[Q] Cortex-A9 Performance Events Counter PMU return Zero

[Q] Cortex-A9 Performance Events Counter PMU return Zero - Samsung Galaxy Nexus

Hello every one,
not sure if this the right place to ask but i really need help.
I am attempting to gather some data on Galaxy Nexus i9250 Android v4.3 CPU ARMv7.I am trying to use ARM Streamline but it provides the following error:
ARM Processor PMU event counters have been detected, however the event counters are reading zeroes. Event counters include those counters listed in the counter configuration options dialog under the core name but exclude the cycle counter (Clock:Cycles) as it is controlled by a dedicated counter. It is possible that the PMU configuration bit DBGEN has not been enabled, and counter values subsequently will always read as zero. To remedy, please update your firmware or Linux kernel to enable DBGEN.
after some search i found similar problem: on freescale
which suggest some modification to the SDER Secure Debug Enable Register, Security Extensions.
i do not know what to so i found a file perf_event in kernel source but not sure where to start.
i found out on infocenter of arm for ARM11 that i should use
// MRC p15, 0, <Rd>, CRn, CRm, opCode_2 ; base
MRC p15, 0, <Rd>, c15, c12, 0 ; Read Performance Monitor Control Register
MCR p15, 0, <Rd>, c15, c12, 0 ; Write Performance Monitor Control Register
this is in perf_event_v6.c kernel folder like this:
static inline unsigned long
armv6_pmcr_read(void)
{
u32 val;
asm volatile("mrc p15, 0, %0, c15, c12, 0" : "=r"(val));
return val;
}
since i'm using version arm7 so i should modify perf_event_v7.c
and my guessing that i should use c9 instead of c15 because this is the option used there and mentioned in the Cortex Reference manual for EX:
c9 registers
Table 4-10 shows the CP15 system control registers you can access when CRn is c9.
Table 4-10 c9 register summary
Op1 CRm Op2 Name Type Reset Description
0 c12 0 PMCR RW 0x41093000 Performance Monitor Control Register
1 PMCNTENSET RW 0x00000000 Count Enable Set Register
2 PMCNTENCLR RW 0x00000000 Count Enable Clear Register
3 PMOVSR RW - Overflow Flag Status Register
4 PMSWINC WO - Software Increment Register
5 PMSELR RW 0x00000000 Event Counter Selection Register
so it should be :
MRC p15, 0, <Rd>, c9, c12, 0 ; Read Performance Monitor Control Register
MCR p15, 0, <Rd>, c9, c12, 0 ; Write Performance Monitor Control Register
and
MRC p15, 0, <Rd>, c9, c12, 5 ; Read PMSELR Register
MCR p15, 0, <Rd>, c9, c12, 5 ; Write PMSELR Register
and to choose the event:
EXPORT pmn_config
; Sets the event for a programmable counter to record
; void pmn_config(unsigned counter, uint32_t event)
; counter (in r0) = Which counter to program (e.g. 0 for PMN0, 1 for PMN1)
; event (in r1) = The event code (from appropriate TRM or ARM Architecture Reference Manual)
pmn_config PROC
AND r0, r0, #0x1F ; Mask to leave only bits 4:0
MCR p15, 0, r0, c9, c12, 5 ; Write PMSELR Register
ISB ; Synchronize context
MCR p15, 0, r1, c9, c13, 1 ; Write PMXEVTYPER Register
BX lr
ENDP
the steps i should follow are as follow:
The following procedure should be followed:
Disable performance counters
Set what each event counter will count
Set cycle counter tick rate
Reset performance counters
Enable performance counters
Call function to profile
Disable performance counters
Read out performance counters
Check that performance counters did not overflow
i also found this EX:
following this code on google_code DirectPMUCodeGCC
i found on e2e support site that Galaxy Nexus is a secure device by checking the DBGAUTHSTATUS
i should push DBGEN or NIDEN high.
but i still did not know how to do it.
Any help?

Related

'Permanent Save' through registry entries

Hi,
I have tried to enable Permanent Save through the following registry values:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\AdvancedCPL
CalendarPassColdBoot = 1
ConnectionPassColdBoot = 1
ConatctPassColdBoot = 1
TaskPassColdBoot = 1
But the entries in hh_cb.exe still are unchecked.
How can I get this etries checked through a selfmade program/registry entries?

Cant modify module IAT to hook API

This may be better served in the development and hacking forum. Mods please move?
I am trying to hook the keybd_event API in the keypad. I have found the address of the import entry for keybd_event in the keypad.dll's IAT. I have done so by disassembling the keypad.dll and finding the offset from an exported function to that IAT entry. At runtime, I have added my own service (in order to get my dll loaded into services.exe). When loaded, I use GetModuleHandle and GetProcAddress to find that exported function then use the known offset to find the IAT entry. I have verified that I have the right memory location by comparing the pointer to the module's location using remote process viewer.
The problem is that I cannot read from or write to the IAT. My code crashes when I try. IsBadReadPtr and IsBadWritePtr tell me that I cant read or write to this memory location. Even a call to VirtualProtect to set it to PAGE_EXECUTE_READWRITE will not work. The call fails. How can I get access to this memory?
This simple test code exe shows that all the memory in the code section of keypad.dll is writeable. As soon as I hit section 2 which contains the IAT The call starts failing. Once I hit section 3 it succeeds again (the hard coded PID and address come from remote process viewer and my service dll; I debugged to find where the read calls fail).
Code:
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
DWORD PID = 239927214, addr = 2061766572, read = 0, sz = 0;
HANDLE pr;
BOOL ans1;
_SetKMode SetKMode;
SetKMode = (_SetKMode)GetProcAddress(GetModuleHandle(L"coredll.dll"), L"SetKMode");
ans1 = SetKMode(true);
pr = OpenProcess(0, 0, PID);
while(ReadProcessMemory(pr, (LPVOID)addr, &read, 4, &sz))
addr++;
while(!ReadProcessMemory(pr, (LPVOID)addr, &read, 4, &sz))
addr++;
while(ReadProcessMemory(pr, (LPVOID)addr, &read, 4, &sz))
addr++;
//ans4 = WriteProcessMemory(pr, ptr2, &mkep, 4, &p4);
CloseHandle(pr);
return 0;
}
What do I need to do to get access? Calls to VirtualProtect and SetKMode do nothing. Any ideas? Thanks!

Nevermind! It seems I was not modifying the correct location. I was trying to modify the table that simply lists imports. I found where the actual function pointer is stored.

Possibility to execute download mode programmatically on Omnia 7?

Us T-Mobile users cannot flash Roms at the minute because the download mode button combo has been disabled.
Maybe there is a way to do this programatically or use a resistor accross certain USB pins like the Galaxy S method.
What's your opinion on this?
Sent from my OMNIA7 using Board Express

Yesterday I wasted some time playing around with the USB diagnostic port (enable in the Diagnosis app, it's the third USB mode option). Both PSAS and QPST can connect to and mess with the phone, so I think if someone knows his way around, the phone can be kicked into Download Mode.
(I only managed to crash the phone in many different ways, but I was really just monkeying around.)

If this can be done it would be great as this is the first phone I have owned where I cannot flash firmware myself.
Might be worth while seeing if everyone with a tmobile uk branded omnia 7 has this issue?
FYI I have included my firmware versions etc so we can try and collate a list of working/non working ones to see what the differences are if any.
os version 7.0.7004.0
firmware revision number 2424.10.10.6
hardware revision number 3.15.0.4
radio software version 2424.10.10.6
radio hardware version 0.0.0.800
bootloader version 4.10.1.9
chip soc version 0.36.2.0

KarmaXXK said:
Yesterday I wasted some time playing around with the USB diagnostic port (enable in the Diagnosis app, it's the third USB mode option). Both PSAS and QPST can connect to and mess with the phone, so I think if someone knows his way around, the phone can be kicked into Download Mode.
(I only managed to crash the phone in many different ways, but I was really just monkeying around.)
Click to expand...
Click to collapse
Yes, I tried the *#7284# code and changed the USB Path Control to "Modem, USB Diag" and my phone was recognised by the ROM Downloader but the phone was not in download mode.
I have stumbled upon something which may be what we are looking for though, after reverse engineering the Samsung Diagnosis app I notice there are codes to access 'Operator Specific' Admin areas in the app. Take a look at the attached image.
Now as you can see, the values listed cannot be typed into the Diagnosis app as there is a formula to decipher them. I have the formula but cannot get it to work.
Code:
Private Overloads Function GetHashCode(ByVal str As String) As UInteger
Dim num As UInteger = 0
For i As Integer = 0 To str.Length - 1
[B]num = ((num << 5) + num) + str(i)[/B]
Next
Return num
End Function
Now the bit highlighted in bold is the bit I cant get to work.
It gives the following error:
Operator '+' is not defined for types 'UInteger' and 'Char'.
Once someone can help to get this working, reversing the formula should in theory show us the correct *#000# code combination for each area.

Fingers crossed you can crack it!

lyriquidperfection said:
Yes, I tried the *#7284# code and changed the USB Path Control to "Modem, USB Diag" and my phone was recognised by the ROM Downloader but the phone was not in download mode.
I have stumbled upon something which may be what we are looking for though, after reverse engineering the Samsung Diagnosis app I notice there are codes to access 'Operator Specific' Admin areas in the app. Take a look at the attached image.
Now as you can see, the values listed cannot be typed into the Diagnosis app as there is a formula to decipher them. I have the formula but cannot get it to work.
Code:
Private Overloads Function GetHashCode(ByVal str As String) As UInteger
Dim num As UInteger = 0
For i As Integer = 0 To str.Length - 1
[B]num = ((num << 5) + num) + str(i)[/B]
Next
Return num
End Function
Now the bit highlighted in bold is the bit I cant get to work.
It gives the following error:
Operator '+' is not defined for types 'UInteger' and 'Char'.
Once someone can help to get this working, reversing the formula should in theory show us the correct *#000# code combination for each area.
Click to expand...
Click to collapse
I worked on this few days ago, I couldn't reverse the hash function but we had some brilliant ideas how to do it (see the stackoverflow thread about it http://stackoverflow.com/questions/4523553/reversing-a-hash-function)
but I used brute force and extracted some 60 diagnosis codes that you can find here http://www.martani.net/2010/12/windows-7-hacks-all-diagnosis-codes-you.html
and here http://www.martani.net/2010/12/windows-7-hacks-all-diagnosis-codes-you_26.html

This is great stuff martani if there is any way to decipher these ones, they may be worth looking at:
g_ADMIN_GENERIC = 3370684588
g_ADMIN_TMOBILE = 469486183
g_ADMIN_VODAFONE = 474092301
These ones indeed look very interesting and may offer a way to enable ADC or even the Download Mode some people like me have been looking for.

lyriquidperfection said:
This is great stuff martani if there is any way to decipher these ones, they may be worth looking at:
g_ADMIN_GENERIC = 3370684588
g_ADMIN_TMOBILE = 469486183
g_ADMIN_VODAFONE = 474092301
These ones indeed look very interesting and may offer a way to enable ADC or even the Download Mode some people like me have been looking for.
Click to expand...
Click to collapse
Actually the code is a little misleading, if you see closely, the enum HashCodeTable is used nowhere.
The app waits for user input, after each "tap" on a number it calls the function ParseDial() that hashes the input with GetHashCode then calls the function GetEnumFromList() on this hashed value.
In GetEnumFromList, there is no use of HashCodeTable and even the codes you provided are not hard-coded in this function. I am not sure why they are there but as far as I can tell, to access these parts of the diagnosis app, you need another method than dialing a code it seems

martani said:
Actually the code is a little misleading, if you see closely, the enum HashCodeTable is used nowhere.
The app waits for user input, after each "tap" on a number it calls the function ParseDial() that hashes the input with GetHashCode then calls the function GetEnumFromList() on this hashed value.
In GetEnumFromList, there is no use of HashCodeTable and even the codes you provided are not hard-coded in this function. I am not sure why they are there but as far as I can tell, to access these parts of the diagnosis app, you need another method than dialing a code it seems
Click to expand...
Click to collapse
Damn it! Looks like we are back to square one!
Have you seen also on the Samsung Galaxy S the Download mode is disabled on some devices, but some users made a jig where you bridge 2 pins with a certain resistor and it knocks the phone into download mode. Maybe this would work on the Omnia 7 also????

I am hoping for a software based fix rather than hacking together something.

**ALL** diagnostic codes for SAMSUNG devices
I reverse engineered the Diagnostic Menu Application. It contains a list of configuration "Titles" with corresponding hash-codes. I made a tool to reverse the hash-codes to dial-codes. The dial-codes may not be the same as some codes that were already known, but the dial-codes are absolutely correct for these menu. Differences are due to hash-collisions (same hash-code may have multiple possible dial-codes). I just used the shortest dial-codes for every menu.
The list of menu's is very long and I discovered that not all menu-codes were not actually implemented. I guess this list of codes is used for all Samsung devices (possibly also for Galaxy S and older Windows Mobile devices). So not all dial-codes may actually work on your device.
WARNING!! The menu's can configure low-level settings of your phone. And if you don't know what you're doing you may brick your device or maybe hard-reset the device and loose all your data and settings. Or you may faulty calibrate your sensors. Be very, very careful with experimenting!! I will not take any responsibility for damaging your device in any way.
I would personally be very interested if anyone finds a way to get the device in download-mode by using these menu's (I have a bad bootloader which does not let my Samsung Omnia 7 go into download-mode to flash it to a newer firmware).
By the way: the admin menu's are NOT implemented on the Omnia 7 :-(
This is the list with menu-titles, dial-codes and their hashcode:
Code:
FTAMain = 15 (0x686)
QUALCOMM TEST = *09# (0x17DB96)
TMOServiceMenu = *74*# (0x31710C2)
SMDINFO = *#03# (0x30C0953)
SIMPLE FUNCTION TEST = *#05# (0x30C0995)
IMEI NUMBER = *#06# (0x30C09B6)
VIEWHISTORYNW = *#07# (0x30C09D7)
LCDTEST = *#0*# (0x30C082A)
QWERTYTEST = *#1*# (0x30C0C6B)
BATT TEST = *#2*# (0x30C10AC)
BRIGHTNESS TEST = *#3*# (0x30C14ED)
TouchDelta 80 = *#80# (0x30C2AF8)
LIGHTTEST = *#12*# (0x648DBCDD)
BTLOGDUMP = *#232# (0x648E4E87)
WIFI FACTORY TEST = *#526# (0x648FEFED)
RILNETLOG = *#638# (0x649080D1)
RILDUMP = *#745# (0x64911110)
VPHONE770 = *#770# (0x64911D2E)
VPHONE771 = *#771# (0x64911D4F)
VPHONE772 = *#772# (0x64911D70)
VPHONE773 = *#773# (0x64911D91)
VPHONE774 = *#774# (0x64911DB2)
VPHONE775 = *#775# (0x64911DD3)
VPHONE776 = *#776# (0x64911DF4)
VPHONE777 = *#777# (0x64911E15)
VPHONE778 = *#778# (0x64911E36)
VPHONE779 = *#779# (0x64911E57)
SR TEST = *#780# (0x6491216F)
VT DUMP = *#938# (0x649225F4)
Disable Testbed = #12358# (0xFC28BE89)
Enable Testbed = *12358# (0x170067D0)
DEBUGMODE1 = *#0011# (0xF63246F2)
BATTERYINFO = *#0228# (0xF63364DC)
PHONELOOPBACKTEST = *#0283# (0xF6337DBD)
AUDIOTEST2 = *#0289# (0xF6337E83)
FMRADIORX = *#0368# (0xF6340241)
LIGHTSENSORTEST = *#0589# (0xF63523A6)
RRCVERSION = *#0599# (0xF63527E7)
AUDIOTEST = *#0673# (0xF635AB00)
SOUNDTEST = *#0675# (0xF635AB42)
RTC = *#0782# (0xF6363B81)
DEVICETEST = *#0842# (0xF636B6DE)
ILLUMINATIONTEST = *#0843# (0xF636B6FF)
MultiTouch = *#0987# (0xF63754E8)
SWversionFTA = *#1111# (0xF644EBD4)
MOUSETEST = *#121*# (0xF645774E)
SWversionEx = *#1234# (0xF645811A)
MOUSECAL = *#123*# (0xF6457FD0)
MOUSECAL06 = *#126*# (0xF6458C93)
GPSTEST = *#1575# (0xF6473762)
MICROUSB TEST = *#1793# (0xF6485864)
HWversionFTA = *#2222# (0xF6579518)
BANDSELECTION = *#2263# (0xF657A63D)
PHONEDUMP = *#2454# (0xF658BADF)
CAMERAUPDATE = *#2470# (0xF658C2DD)
CAMERADISABLE = *#2480# (0xF658C71E)
NAVIKEY TEST = *#2486# (0xF658C7E4)
INTEGRITY = *#2580# (0xF659537F)
TouchFirmare 2663 = *#2663# (0xF659D7C1)
TouchDelta 2664 = *#2664# (0xF659D7E2)
TouchDelta 2665 = *#2665# (0xF659D803)
RILNETLOG OFF = *#6380# (0xF6A09CC1)
RILNETLOG ON = *#6381# (0xF6A09CE2)
NETLOCK NETWORK = *#6955# (0xF6A3DAE9)
USBPATHCHANGE = *#7284# (0xF6B22965)
POWERONATTACH = *#7298# (0xF6B22E2A)
SELF DIAGNOSTIC MODE = *#7353# (0xF6B2A8E2)
DebugOption = *#7450# (0xF6B334E0)
ERROR REPORT ON = *#7451# (0xF6B33501)
ERROR REPORT VERIFY = *#7452# (0xF6B33522)
NETLOCK SERVICE = *#7755# (0xF6B4DAA8)
VPHONE DISABLED = *#77*0# (0xF6B4AB38)
VPHONE ENABLED = *#77*1# (0xF6B4AB59)
UARTCHANGER = *#9090# (0xF6D54562)
DEBUGDUMP = *#9900# (0xF6DA0E82)
PILEDUMP = *#9901# (0xF6DA0EA3)
NETLOG LOG START = *#9905# (0xF6DA0F27)
DEBUG RIL DUMP = *#9906# (0xF6DA0F48)
ERRORREPCAB INSTALL = *#9907# (0xF6DA0F69)
GUMITEST3G CAB INSTALL = *#9908# (0xF6DA0F8A)
SUWON3G CAB INSTALL = *#9909# (0xF6DA0FAB)
UARTPATH = *#9910# (0xF6DA12C3)
BATTERYMONITOR = *#9911# (0xF6DA12E4)
CONNECTION SETTING = *#9920# (0xF6DA1704)
VERIFYCOMPARE = *#9990# (0xF6DA34CB)
YSSHINTEST = *#9999# (0xF6DA35F4)
VersionScript = 19104#2* (0xD21FC43E)
BLUETOOTH LOG DISABLE = 20652609 (0x1598F3DE)
BLUETOOTH LOG ENABLE = 20652619 (0x1598F3FF)
BT SSPDEbugModeEnable = 20652629 (0x1598F420)
BT SSPDEbugModeDisable = 20652639 (0x1598F441)
OMADMCLIENT LOG DISABLE = 20653609 (0x1599803F)
OMADMCLIENT LOG ENABLE = 20653619 (0x15998060)
CELOG LOG DISABLE = 20654609 (0x159A0CA0)
CELOG LOG ENABLE = 20654619 (0x159A0CC1)
TOTALCALLTIME = 2934331* (0xC35403F3)
RESET CUSTOM = 35180948 (0x77496B66)
RESET FACTORY = 35190718 (0x775B7B02)
ERASE IMEIITEM = 35190728 (0x775B7B23)
IMEI ADJUST = 35190738 (0x775B7B44)
BLUETOOTH RF TEST = 3##65*88 (0xECE73A9E)
BLUETOOTH AUDIO TEST = 3##65*98 (0xECE73ABF)
AutoSimSetting = 40*047#3 (0xD1C556DF)
PVKKey = 40*549#3 (0xD21FD9E6)
RESET FACTORY WITHDEFAULTLANGUAGE = 76264513 (0x777E1362)
NONSLEEPCALL OFF = *#069*0# (0xBCEBFF49)
NONSLEEPCALL ON = *#069*1# (0xBCEBFF6A)
LEDTEST = *#14789# (0xBF1C1ADD)
DMSessionInit = *#15428# (0xBF2C7494)
CIPHERING = *#32489# (0xC3A095FA)
CAMERAUPDATESVC = *#32589# (0xC3A1225B)
LOGDUMPMGR = *#33284# (0xC3B19514)
SR DISABLED = *#780*0# (0xCD5F5D49)
SR ENABLED = *#780*1# (0xCD5F5D6A)
NETLOCK SUBSET = *#78255# (0xCD60A57B)
LAUNCH UAEDIT = *#92782# (0xD1A12DFC)
PdaBuildTime = *#99820# (0xD2204C1C)
VersionTime = *#99821# (0xD2204C3D)
WIFI TEST = 0373385#6 (0xECE73BA6)
EN LOCK NW = 074578132 (0xBBF27D35)
GCFTESTMODE ENTER = 086#58023 (0x1807BAE3)
FILE SYSTEM TEST = 089559715 (0x28F3F681)
AUDIOGAINCONTROL = 08#766104 (0x902D68E3)
DIS LOCK SUB NW = 17#991#3* (0x1D45A6AE)
PVKFileName = 18*357#25 (0x161B193C)
EN LOCK SUB NW = 193582504 (0xBC073A15)
GPSTESTTOOL = 1#8865#55 (0xF61EC09C)
EN LOCK CORP = 1*0273411 (0xF62C007D)
EN LOCK SVC = 1*0278411 (0xF62EBE62)
DIS LOCK NW = 20789802* (0x1D30E9CE)
SellOutSMS = 2615#0922 (0xD04CA8DE)
TFlashUnPairing = 30334*733 (0x51B892C4)
DIS LOCK SVC = 38025*93# (0xCA957BDB)
GPSTESTTOOL2 = 400#40*08 (0xB9F6D60D)
GPSTESTXTRA = 400#40*18 (0xB9F6D62E)
SerialNumber = 5317*0648 (0x6E256D8C)
EN LOCK SIM = 5494585*3 (0xBC051995)
SERVERURL = 553378683 (0xD8389060)
SLIDECOUNT = 584644021 (0xF0BF3052)
SellOutSMSTestMode = 597#*224# (0x96E7B26D)
APPSLAUNCHER = 5**6244*3 (0x33B0B76)
SLOGSERIAL M2 = 66#6757#1 (0x7050E07C)
AutoReceive Enable = 7160*5088 (0xEF2C5E0D)
TESTMODE = 718071#49 (0x8A09ACC8)
RESET SERVICE = 72673#00# (0xEC5B4BEF)
ReactivateSellOutSMS = 74201#086 (0x807DB65F)
AUDIOCODEC = 7#16#1#37 (0x902D68C2)
ADMIN GENERIC = 838*5448* (0xC8E890AC)
SLOGSERIAL ALL ON = 8644*3081 (0x705107AC)
VT MANUALSETTING = 8802*7*5# (0x104384B5)
DISLOCK SIM = 98217*243 (0x1D43862E)
DMTESTMENU = 9#7357764 (0x414D9633)
SLOGSERIAL ALL OFF = #22#6214# (0x7050E03A)
SLOGSERIAL M1 = #22#6215# (0x7050E05B)
SLOGSERIAL M3 = #22#6217# (0x7050E09D)
SLOGSERIAL M4 = #22#6218# (0x7050E0BE)
SLOGSERIAL M5 = #22#6219# (0x7050E0DF)
ADMIN VODAFONE = #75471648 (0x1C42130D)
DisableSellOutSMS = *4587*676 (0x903477AF)
BLUETOOTH SEARCH TEST = *#232333# (0xECE73AE0)
RANDOM BT MAC = *#232336# (0xECE73B43)
BLUETOOTH MAC VIEWER = *#232337# (0xECE73B64)
WIFI MAC VIEWER = *#232338# (0xECE73B85)
PRECONFIGURATION = *#638738# (0x213EF313)
SELF DIAGNOSTIC MODE DISABLE = *#7353*0# (0x6E008D7C)
SLOGSERIAL M6 = *#745*06# (0x7050E100)
DIS LOCK CORP = 00*2*2#524 (0xCA92BDF6)
ADMIN TMOBILE = 0612824763 (0x1BFBCA67)
AutoReceive Disable = 09925572#3 (0xD4B8217D)
SWversionIn = 1309653522 (0xECB23FC4)
GPSTTFFTESTTOOL = 154*068271 (0xF61EBC7C)
SellOutSMSProductionMode = 1#3341#5#0 (0x96D7C68A)
LOCK STATUS INFO = 28##**23*0 (0x7D8C72E3)
SWversionNewIn = 32456464#7 (0xFD58D7FC)

Heathcliff74 said:
I reverse engineered the Diagnostic Menu Application. It contains a list of configuration "Titles" with corresponding hash-codes. I made a tool to reverse the hash-codes to dial-codes. The dial-codes may not be the same as some codes that were already known, but the dial-codes are absolutely correct for these menu. Differences are due to hash-collisions (same hash-code may have multiple possible dial-codes). I just used the shortest dial-codes for every menu.
Click to expand...
Click to collapse
Can you share how did you reverse the hash function? I worked on this some time ago but finally just brute forced it to extract the keys.

I would also like to know how he reversed the hash codes! I tried for hours and had no luck!

Haha.. Well, I first tried to calculate the original dial-codes, but that seems to work only for dialcodes shorter than 8 digits (5 bits per digit, 32 bits hash-code = 32 / 5 = 7 digits + 1 digit for the extra add):
Code:
uint hash = 0; // enter hash here
string DialCode = "";
while (hash > 0)
{
uint digit = (hash % 33) + 33;
if (digit > hash)
hash = 0;
else
hash = (hash - digit) / 33;
DialCode = Convert.ToChar(digit) + DialCode;
}
return DialCode;
But this does not work for long dial-codes. So after that I just made a little program to brute-force it. I copied the enum with menu-titles and hash-codes to my project. Then I used reflection to populate a sortedlist. Then I started to brute-force and check all dialcodes for their hashcode and see if it exists in the list. If it exists, I add it to a textbox and remove the item from the list. That's it. So it is not really reversed, but my program took about an hour to get dial-codes for all the hashcodes in the enum.
Code:
SortedList<uint, string> hashCodes = new SortedList<uint, string>();
int l = typeof(HashCodeTable).GetEnumNames().Length;
string[] menunames = typeof(HashCodeTable).GetEnumNames();
for (int i = 0; i < l; i++)
{
try
{
hashCodes.Add(Convert.ToUInt32(Enum.Parse(typeof(HashCodeTable), menunames[i])), menunames[i].Substring(2).Replace('_', ' '));
}
catch { }
}
char[] chars = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '#', '*' };
for (int length = 1; length <= 20; length++)
{
ushort[] digits = new ushort[length];
for (int i = 0; i < length; i++) digits[i] = 0;
while (true)
{
// calc hash
uint hashCode = 0;
for (int i = 0; i < length; i++)
{
hashCode = ((hashCode << 5) + hashCode) + chars[digits[i]];
}
if (hashCodes.ContainsKey(hashCode))
{
int m = hashCodes.IndexOfKey(hashCode);
string str = "";
for (int j = 0; j < length; j++)
str = str + chars[digits[j]];
textBox1.Text = textBox1.Text + hashCodes.Values[m] + " = " + str + " (0x" + hashCode.ToString("X") + ")" + Environment.NewLine;
hashCodes.RemoveAt(m);
}
// increase
digits[length - 1]++;
for (int k = length - 1; k >= 0; k--)
{
if (digits[k] >= 12)
{
if (k == 0)
break;
else
{
digits[k] -= 12;
digits[k - 1]++;
}
}
}
if ((digits[0] >= 12) || (hashCodes.Count == 0)) break;
}
if (hashCodes.Count == 0) break;
}

Excellent stuff! Thank you for this very interesting code snippit!

WP7 diag codes
martani said:
Actually the code is a little misleading, if you see closely, the enum HashCodeTable is used nowhere.
Click to expand...
Click to collapse
This is because the compiler optimized out the switch statement and compiled the constants into the IL code for the hash codes.
Within the main switch statement where keypad entries are evaluated there are ~112 codes and I've reversed all of them. Writing hash algorithms is not straightforward and it's quite a simple one, since my app captured 2-3-4 variants of keycodes for the same hash value.
Regarding the most interesting entries at the top of the enum the ADMIN_ entries...those hash values are not handled by the application, maybe Samsung has another diag app or a different app which is using the same method.
The other thing I can think of is there are APIs in the diag app which one is sending the hash of a keycode to the given driver...I tried that but the ADMIN stuff did not worked that way either :-((
If anyone is interested I can post the resolved codes, but not sure if I can post it in the forum or not ;-)

Regsitry entry to enable SLDR mode
I found this definition in B44C7A84-5068-4b43-A1E5-F870A80F6FF8.rgu:
[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\UsbFn]
...
"OsMode"=dword:0 ; 0 for Main OS, 1 for SLDR
....
Is the download mode == SLDR mode?
Since maybe we can set this entry "somehow", and upon next reboot we will get into download mode so we can flash the device?
So the question is, what is SLDR mode? Secure Loader mode? I don't know this, a more pro in this area should help out ;-)
UPDATE
I was able to read the value (0) and write it back (0). Did not tried to write 1 there

Hey guys. I know this thread is about programmatically enter downloadmode, but I wanted to try the 301k resistor trick and I can confirm it works on Samsung Omnia 7.
I used this guide. If you're gonna do that too, then you should pay attention to these things:
- The guide refers to pin 4 and 5 being closest to the headphone socket. But on the omnia 7, the headphone and micro-usb sockets are the other way around if you compare it to the Galaxy S. The guide is for the Galaxy S, so you should really pay attention to which pins you solder the resistor(s). This is the best picture on how you should solder the resistor(s).
- Many micro-usb cables have no wire for pin 4. Some connectors don't even have a pin 4. You should first verify that your connector has all 5 pins. If you only have 4 wires, then you have to dismantle the connector and solder directly on the back of the connector.
I switched off my Omnia 7. I plugged in my jig and it went to downloadmode immediately.
It's late now, so I will see tomorrow what I will be going to flash on it. There quite a few roms and I'm not sure which one I should use. I have to figure that out first.
If anyone has questions about how to make a jig, just ask. I know how to make one now.

You should post pictures, how to make such a cable. Thanks

FromOuterSpace said:
You should post pictures, how to make such a cable. Thanks
Click to expand...
Click to collapse
The picture I linked to in my previous post look pretty clear to me. It shows what pins you have to use. The guide I linked to contain all the other necessary details. If you have any specific questions about something that is still not clear, you can ask me.

[MOD/SETTINGS TWEAK] SiRF GPS on SGS2

This is the updated sirfgps.conf file ONLY for ICS and has been modded by myself. As the GPS serial port is changed in ICS ROM.
#CSR SiRF plc
#PROJECT_NAME : white Space is not allowed
#UART_DRIVER : Uart Driver Path
#RESET_GPIO : Reset GPIO Driver Path
#ONOFF_GPIO : OnOff GPIO Driver Path
#EXTERNAL_LNA : 1 - use External LNA, 0 - use Internal LNA only
#REF_CLOCK_26MHZ: 1 - use 26MHz TCXO, 0 - use 16.369MHz TCXO
#UART_BAUD_RATE : 0 - 115200bps 1 - 230400, 2 - 460800, 3 - 57600
#FREQUENCY_AIDING : 0 - Disable, 1 - Enable
#SENSOR_AIDING : 0 - Disable, 1 - Enable
#SET_ID_IMSI : 1 - Use IMSI for SET ID, 0 - Use MSISDN for SET ID, especially for Japan Network Operators
#DEBUGGING_FILES : 0 - no log file, 1 - log files enabled
#SSL_ENABLED : 0 - SSL Disabled, 1 - SSL Enabled
#CERTI_VERSION : 0 - TLSv1 , 1 - SSLv3 , 2 - SSLv23
#CP_RESPONSETIME : 0 - no priority, 1 - resposne priority time, 2 - resposne priority position ,3 - resposne priority use entire response time
#REAIDING=20
#CONTROL_PLANE : 1 - CP Enabled, 0 - CP Disabled, for MP3 player or PND
#ATT_NETWORK_OPERATOR : 1 - for AT&T, 0 - for other network operator
#SGEE : 1 - SGEE ENABLE 0 - SGEE DISABLE
PROJECT=SAMSUNG_S5PC210
UART_DRIVER=/dev/ttySAC1
RESET_GPIO=/sys/devices/virtual/sec/gps/GPS_nRST/value
ONOFF_GPIO=/sys/devices/virtual/sec/gps/GPS_PWR_EN/value
REAIDING=20
EXTERNAL_LNA=1
REF_CLOCK_26MHZ=1
UART_BAUD_RATE=2
FREQUENCY_AIDING=1
SENSOR_AIDING=1
SET_ID_IMSI=1
DEBUGGING_FILES=0
SSL_ENABLED=1
CERTI_VERSION=1
CP_RESPONSETIME=3
CONTROL_PLANE=1
ATT_NETWORK_OPERATOR=0
ICS_NETWORK_OPERATOR=0
EMC_ENABLE=1
CIQ_ENABLE=1
SGEE=1
CGEE=1
LOG_PATH=/data
Click to expand...
Click to collapse
======================================
I meddled with the stock SGS KH3 firmware and found this file inside (/etc/sirfgps.conf).
It got so many settings for GPS chipset but is untouched by AngryGPS program or any system's GPS settings, it must be edited manually.
I noticed a big differences by turning on this sensor aiding, freq aid, and emc feature in this file.
I do notice that sensor aiding is toggleable in the system's setting but it only work in software level and this conf file is in hardware level.
If any of you want the edited file, let me know and I'll post it for you.
============================================

Please share, I'm curious about your discovery
Sent from my htc.desireZED

Yes. It would be nice if you posted the updated file.

This is the mentioned file found in my stock rooted /etc folder. Modified of course...
Permission is rw-r--r--
Group is root|root

hm I m looking for difference and you switch AIDING to ON manuall but when I enable in setting>>location>>use sensors- It is the same I think .)

Crescendo Xenomorph said:
This is the mentioned file found in my stock rooted /etc folder. Modified of course...
Permission is rw-r--r--
Group is root|root
Click to expand...
Click to collapse
This looks interesting, but unfortunately the zip file seems to be corrupt. Can you please re-upload the file?

I just trying to open the file and it works OK.
Try to extract it using WinRAR. I compressed it via WinRAR.
Hmm, when I enable the sensor aiding in the location menu, the sensor aiding in that conf file is still 0. When I disable it, the file also says 0. The last modified time is months ago, which is before I activate this device.
I notice the faster fix (mainly when you try to get a cold fix inside a fast moving car) and slight improvement in accuracy.
The interesting settings are: frequency aiding and emc feature.
I dunno what it's for but it improve my lock time and accuracy.

#CSR SiRF plc
#PROJECT_NAME : white Space is not allowed
#UART_DRIVER : Uart Driver Path
#RESET_GPIO : Reset GPIO Driver Path
#ONOFF_GPIO : OnOff GPIO Driver Path
#EXTERNAL_LNA : 1 - use External LNA, 0 - use Internal LNA only
#REF_CLOCK_26MHZ: 1 - use 26MHz TCXO, 0 - use 16.369MHz TCXO
#UART_BAUD_RATE : 0 - 115200bps 1 - 230400, 2 - 460800, 3 - 57600
#FREQUENCY_AIDING : 0 - Disable, 1 - Enable
#SENSOR_AIDING : 0 - Disable, 1 - Enable
#SET_ID_IMSI : 1 - Use IMSI for SET ID, 0 - Use MSISDN for SET ID, especially for Japan Network Operators
#DEBUGGING_FILES : 0 - no log file, 1 - log files enabled
#SSL_ENABLED : 0 - SSL Disabled, 1 - SSL Enabled
#CERTI_VERSION : 0 - TLSv1 , 1 - SSLv3 , 2 - SSLv23
#CP_RESPONSETIME : 0 - no priority, 1 - resposne priority time, 2 - resposne priority position ,3 - resposne priority use entire response time
#REAIDING=20
#CONTROL_PLANE : 1 - CP Enabled, 0 - CP Disabled, for MP3 player or PND
#ATT_NETWORK_OPERATOR : 1 - for AT&T, 0 - for other network operator
PROJECT=SAMSUNG_S5PC210
UART_DRIVER=/dev/s3c2410_serial1
RESET_GPIO=/sys/devices/virtual/sec/gps/GPS_nRST/value
ONOFF_GPIO=/sys/devices/virtual/sec/gps/GPS_PWR_EN/value
EXTERNAL_LNA=1
REF_CLOCK_26MHZ=1
UART_BAUD_RATE=2
FREQUENCY_AIDING=1
SENSOR_AIDING=1
SET_ID_IMSI=1
DEBUGGING_FILES=0
SSL_ENABLED=0
CERTI_VERSION=0
CP_RESPONSETIME=2
CONTROL_PLANE=1
ATT_NETWORK_OPERATOR=0
EMC_ENABLE=1
LOG_PATH=/sdcard/gps/csr

Testing
Hi,
I have tried this trick, but i saw no difference ...Inside my car (i have those "heat-protected" windows) i still have problems, my accuracy is awful, usually between 15-20 m in an open road (with spots of 5-10 m), and 25-30 m inside the city (which makes it useless).
I have changed the UART_BAUD to 3 and i will test it later....the reason is that i realized that when i turn right/left with my car, or in the road when a curve is closed enough to generate "centrifugal force" the accuracy drops from 10 m to 25 m and then when i come back to a straight lane the precision goes down to "normal" values....so i reduced BAUD to minimum, it will be slower but i hope more stable....
I'll try and post my results tomorrow

Crescendo Xenomorph said:
#CSR SiRF plc
#PROJECT_NAME : white Space is not allowed
#UART_DRIVER : Uart Driver Path
#RESET_GPIO : Reset GPIO Driver Path
#ONOFF_GPIO : OnOff GPIO Driver Path
#EXTERNAL_LNA : 1 - use External LNA, 0 - use Internal LNA only
#REF_CLOCK_26MHZ: 1 - use 26MHz TCXO, 0 - use 16.369MHz TCXO
#UART_BAUD_RATE : 0 - 115200bps 1 - 230400, 2 - 460800, 3 - 57600
#FREQUENCY_AIDING : 0 - Disable, 1 - Enable
#SENSOR_AIDING : 0 - Disable, 1 - Enable
#SET_ID_IMSI : 1 - Use IMSI for SET ID, 0 - Use MSISDN for SET ID, especially for Japan Network Operators
#DEBUGGING_FILES : 0 - no log file, 1 - log files enabled
#SSL_ENABLED : 0 - SSL Disabled, 1 - SSL Enabled
#CERTI_VERSION : 0 - TLSv1 , 1 - SSLv3 , 2 - SSLv23
#CP_RESPONSETIME : 0 - no priority, 1 - resposne priority time, 2 - resposne priority position ,3 - resposne priority use entire response time
#REAIDING=20
#CONTROL_PLANE : 1 - CP Enabled, 0 - CP Disabled, for MP3 player or PND
#ATT_NETWORK_OPERATOR : 1 - for AT&T, 0 - for other network operator
PROJECT=SAMSUNG_S5PC210
UART_DRIVER=/dev/s3c2410_serial1
RESET_GPIO=/sys/devices/virtual/sec/gps/GPS_nRST/value
ONOFF_GPIO=/sys/devices/virtual/sec/gps/GPS_PWR_EN/value
EXTERNAL_LNA=1
REF_CLOCK_26MHZ=1
UART_BAUD_RATE=2
FREQUENCY_AIDING=1
SENSOR_AIDING=1
SET_ID_IMSI=1
DEBUGGING_FILES=0
SSL_ENABLED=0
CERTI_VERSION=0
CP_RESPONSETIME=2
CONTROL_PLANE=1
ATT_NETWORK_OPERATOR=0
EMC_ENABLE=1
LOG_PATH=/sdcard/gps/csr
Click to expand...
Click to collapse
I dont think this will make much difference.. on my phone anyway if you look at the line
Crescendo Xenomorph said:
UART_DRIVER=/dev/s3c2410_serial1
Click to expand...
Click to collapse
looking in that file location there is no such driver present..

I DO have the s3c2410_serial1 file on that location....And a serial0, serial2, serial3 and serial4
I dont really know if this is doing something or not...I tried to enable debugging and i see no file created on sdcard

But why Samsung put that file inside their ROM?

Hi,
this works for me, gps fix in 10sec.
with friendly greet
starbase64

So you only copy sirfgps to /etc and not more?
Thanks. Sounds interesting.
Sent from my GT-I9100 using XDA App

lynx2k50 said:
So you only copy sirfgps to /etc and not more?
Thanks. Sounds interesting.
Sent from my GT-I9100 using XDA App
Click to expand...
Click to collapse
yes
german forum: http://goo.gl/o2aa4

IN new italian ROM LA2 2.3.6
Code:
#CSR SiRF plc
#PROJECT_NAME : white Space is not allowed
#UART_DRIVER : Uart Driver Path
#RESET_GPIO : Reset GPIO Driver Path
#ONOFF_GPIO : OnOff GPIO Driver Path
#EXTERNAL_LNA : 1 - use External LNA, 0 - use Internal LNA only
#REF_CLOCK_26MHZ: 1 - use 26MHz TCXO, 0 - use 16.369MHz TCXO
#UART_BAUD_RATE : 0 - 115200bps 1 - 230400, 2 - 460800, 3 - 57600
#FREQUENCY_AIDING : 0 - Disable, 1 - Enable
#SENSOR_AIDING : 0 - Disable, 1 - Enable
#SET_ID_IMSI : 1 - Use IMSI for SET ID, 0 - Use MSISDN for SET ID, especially for Japan Network Operators
#DEBUGGING_FILES : 0 - no log file, 1 - log files enabled
#SSL_ENABLED : 0 - SSL Disabled, 1 - SSL Enabled
#CERTI_VERSION : 0 - TLSv1 , 1 - SSLv3 , 2 - SSLv23
#CP_RESPONSETIME : 0 - no priority, 1 - resposne priority time, 2 - resposne priority position ,3 - resposne priority use entire response time
#REAIDING=20
#CONTROL_PLANE : 1 - CP Enabled, 0 - CP Disabled, for MP3 player or PND
#ATT_NETWORK_OPERATOR : 1 - for AT&T, 0 - for other network operator
#SGEE : 1 - SGEE ENABLE 0 - SGEE DISABLE
PROJECT=SAMSUNG_S5PC210
UART_DRIVER=/dev/s3c2410_serial1
RESET_GPIO=/sys/devices/virtual/sec/gps/GPS_nRST/value
ONOFF_GPIO=/sys/devices/virtual/sec/gps/GPS_PWR_EN/value
EXTERNAL_LNA=1
REF_CLOCK_26MHZ=1
UART_BAUD_RATE=2
FREQUENCY_AIDING=0
SENSOR_AIDING=0
SET_ID_IMSI=1
DEBUGGING_FILES=0
SSL_ENABLED=0
CERTI_VERSION=0
CP_RESPONSETIME=2
CONTROL_PLANE=1
ATT_NETWORK_OPERATOR=0
ICS_NETWORK_OPERATOR=0
EMC_ENABLE=0
CIQ_ENABLE=0
SGEE=1
LOG_PATH=/sdcard/gps/csr
This line are new:
ICS_NETWORK_OPERATOR=0
CIQ_ENABLE=0
SGEE=1

Hi,
Please would someone post the original settings as my GPS will not lock at all now and I would like to reset them.
Thanks

From stock rom..
#CSR SiRF plc
#PROJECT_NAME : white Space is not allowed
#UART_DRIVER : Uart Driver Path
#RESET_GPIO : Reset GPIO Driver Path
#ONOFF_GPIO : OnOff GPIO Driver Path
#EXTERNAL_LNA : 1 - use External LNA, 0 - use Internal LNA only
#REF_CLOCK_26MHZ: 1 - use 26MHz TCXO, 0 - use 16.369MHz TCXO
#UART_BAUD_RATE : 0 - 115200bps 1 - 230400, 2 - 460800, 3 - 57600
#FREQUENCY_AIDING : 0 - Disable, 1 - Enable
#SENSOR_AIDING : 0 - Disable, 1 - Enable
#SET_ID_IMSI : 1 - Use IMSI for SET ID, 0 - Use MSISDN for SET ID, especially for Japan Network Operators
#DEBUGGING_FILES : 0 - no log file, 1 - log files enabled
#SSL_ENABLED : 0 - SSL Disabled, 1 - SSL Enabled
#CERTI_VERSION : 0 - TLSv1 , 1 - SSLv3 , 2 - SSLv23
PROJECT=SAMSUNG_U1
UART_DRIVER=/dev/s3c2410_serial1
RESET_GPIO=/sys/devices/virtual/sec/gps/GPS_nRST/value
ONOFF_GPIO=/sys/devices/virtual/sec/gps/GPS_PWR_EN/value
EXTERNAL_LNA=1
REF_CLOCK_26MHZ=1
UART_BAUD_RATE=2
FREQUENCY_AIDING=1
SENSOR_AIDING=0
SET_ID_IMSI=1
DEBUGGING_FILES=0
SSL_ENABLED=0
CERTI_VERSION=0

Crescendo Xenomorph said:
But why Samsung put that file inside their ROM?
Click to expand...
Click to collapse
did you try to use an external SiRFIII GPS through BT, maybe it's for that....

Crescendo Xenomorph said:
Hmm, when I enable the sensor aiding in the location menu, the sensor aiding in that conf file is still 0. When I disable it, the file also says 0. The last modified time is months ago, which is before I activate this device.
Click to expand...
Click to collapse
Most likely there is an interface (maybe a control socket?) that allows these settings to be overridden by the Settings app without changing the file.
To confirm if the file is even used (sometimes cruft makes it into a ROM for no good reason...), try changing the serial port from s3c2410_serial1 to something else - it should completely break things. If it does not totally break things, then the file is most likely not used.

100% Working WiFi Monitor Mode

This article will first describe how to locate the Monitor mode code in Nexus 5 firmware (hammerhead-ktu84p-factory-35ea0277, bootloader-hammerhead-hhz11k : c32f8bec310c659c1296739b00c6a8ac). Then, we will try to understand what it does (its functionalities). Finally, you will have to find bugs by yourself because I didn't find any...so far !
Note: Terms (Non-)Secure world & (Non-)Secure state are used as synonyms. Term Normal world is also used as synonym of Non-Secure world.
I. Quick introduction to ARM Security Extensions
"The Security Extensions define two security states: Secure state and Non-secure state. All instruction execution takes place either in Secure state or in Non-secure state.[...] The Security Extensions also define an additional processor mode, Monitor mode, that provides a bridge between software running in Non-secure state and software running in Secure state."
"The Secure Monitor Call exception is implemented only as part of the Security Extensions. The Secure Monitor Call instruction, SMC , requests a Secure Monitor function, causing the processor to enter Monitor mode."
"When an exception is taken, processor execution is forced to an address that corresponds to the type of exception. This address is called the exception vector for that exception. A set of exception vectors comprises eight consecutive word-aligned memory addresses, starting at an exception base address. These eight vectors form a vector table."
-- ARM Architecture Reference Manual ARMv7-A
II. OpenSource TrustZone examples
Trusted Execution Environment (TEE) is the "small" secure kernel executed in Secure state. The Monitor code is part of the TEE code.
To get an idea of how the Monitor code works, we can take a look at two TrustZone examples:
Cortex-A9 TrustZone example by ARM : a simple example of secure and non-secure code that communicates through Monitor mode.
OP-TEE by STMicroelectronics : an Open Source TEE 1.0 implementation.
After studying these code samples, we can clearly distinguish two parts in Monitor code:
Monitor mode initialization: called once, at TEE initialization time.
In this code, we can notice two specific instructions :
Monitor Vector Base Address Register (MVBAR) setup: MVBAR contains the Monitor vector table address. Both samples use the same instructions to setup MVBAR :
MCR p15, 0, $RX,c12,c0, 1
where $RX is a pointer to the monitor mode's vector table.
SP register setup: the Monitor mode stack address is set into SP register. This register is banked, which means this value will be automatically restored next time the processor enters in Monitor mode.
Exception vectors: called when an exception is taken to Monitor mode.
Both samples implement a simple Secure Monitor Call (SMC) handler that switches between the normal and secure worlds when a SMC call is made. As SMC handler is an entry point to the Secure state, it would be interesting to analyze it in Nexus 5 firmware.
III. Extracting Nexus 5 firmware
We know that the Monitor code may be embedded into the TEE image. In the case of Nexus 5, this image can be extracted from stock ROM.
h t t p s: / / w w w . y o u t u b e . c o m /w a t c h ? v = h 6 c K G j X K S j I
h t t p s : / / w w w . y o u t u b e . c o m / w a t c h ? v = P R K y k F U Q K m 0
Once downloaded, we use a small tool to unpack bootloader-hammerhead-hhz11k.img file. One of extracted files is an ELF ARM binary named "tz".
IV. Nexus 5 Monitor mode code
To analyze the Nexus 5 TrustZone binary, we can use IDA Demo 6.6.
Given that setting up MVBAR is very specific to the monitor mode's initialization code, we use it to locate the Monitor mode's initialization code in Nexus 5 TrustZone binary.
Using IDA regex search in code disassembly, we look for the instruction used to write MVBAR :
MCR[[:space:]]+p15, 0, [^,]+,c12,c0, 1
This search returns only 3 occurrences, and one of them also sets the SP register. These instructions are expected to be found in Monitor mode initialization code.
IV.1. Monitor mode initialization function
Here's the disassembly of the Monitor mode initialization code :
LOAD:FE80DB4C init_monitor
LOAD:FE80DB4C MSR CPSR_c, #0xD6 ; switch to Monitor mode
LOAD:FE80DB50 LDR R0, =monitor_vector_table ; load monitor vector table ptr into R0
LOAD:FE80DB54 MCR p15, 0, R0,c12,c0, 1 ; write R0 to MVBAR
LOAD:FE80DB58 BL sub_FE80DB88 ; initialize Non-Secure world
LOAD:FE80DB5C LDR SP, =0xFE82B700
LOAD:FE80DB60 MRC p15, 0, R0,c0,c0, 5 ; write MPIDR value to R0
LOAD:FE80DB64 AND R0, R0, #0xFF ; keep Affinity level 0 : current virtual CPU id
LOAD:FE80DB68 MOV R1, #0x200
LOAD:FE80DB6C MUL R1, R1, R0 ; compute stack offset for current vCPU
LOAD:FE80DB70 SUB SP, SP, R1 ; setup Monitor stack register SP
LOAD:FE80DB74 MOV R0, #0b100
LOAD:FE80DB78 MCR p15, 0, R0,c1,c1, 0 ; set FIQ flag in SCR register
LOAD:FE80DB7C ISB SY ; flush the pipeline in the processor
LOAD:FE80DB80 MSR CPSR_c, #0xD3 ; switch to Supervisor mode
LOAD:FE80DB84 BX LR
LOAD:FE80DB84 ; End of function init_monitor
We will now proceed to a detailed analysis of each step.
IV.1.A Switch to Monitor mode
MSR instruction moves an immediate value (here 0xD6) to a Special register (here CPSR_c).
LOAD:FE80DB4C MSR CPSR_c, #0xD6 ; switch to Monitor mode
The Current Program Status Register (CPSR) holds processor status and control information. CPSR with "_c" suffix enables writing of bits<0:7> of CPSR (ARM Ref. B9.3.11). This bitfield controls the processor mode and exception masks.
We can use a simple IDAPython script to replace the immediate value 0xD6 with symbols documented in ARM Ref. (B1-1148) :
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
from idautils import *
from idaapi import *
from idc import *
Message("%s starting...\n" % __file__)
CPSR_C_enum_id = GetEnum("CPSR_C_enum")
if CPSR_C_enum_id == BADADDR:
CPSR_C_enum_id = AddEnum(-1, "CPSR_C_enum", hexflag())
SetEnumBf(CPSR_C_enum_id,1);
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_USR", 0b10000, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_FIQ", 0b10001, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_IRQ", 0b10010, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_SVC", 0b10011, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_MON", 0b10110, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_ABT", 0b10111, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_HYP", 0b11010, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_UND", 0b11011, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_MODE_SYS", 0b11111, 0x1F)
AddConstEx(CPSR_C_enum_id,"CPSR_THUMB", 0x20, 0x20)
AddConstEx(CPSR_C_enum_id,"CPSR_MASK_FIQ", 0x40, 0x40)
AddConstEx(CPSR_C_enum_id,"CPSR_MASK_IRQ", 0x80, 0x80)
ea = MinEA()
while True:
ea= FindText(ea, SEARCH_DOWN|SEARCH_NEXT|SEARCH_REGEX, 0, 0, " (CPS|MSR) ")
if ea == BADADDR:
break
mnem = GetMnem(ea)
if mnem == "MSR":
if GetOpnd(ea, 0) == "CPSR_c" and GetOpType(ea, 1) == o_imm:
OpEnumEx(ea, 1, CPSR_C_enum_id, 0)
Message("%s MSR CPSR_c, %s\n" % (hex(ea),GetOpnd(ea, 1)))
elif mnem == "CPS":
OpEnumEx(ea, 0, CPSR_C_enum_id, 0)
Message("%s CPS %s\n" % (hex(ea),GetOpnd(ea, 0)))
else:
Message("Unrecognized instruction @ %s : %s\n" % (hex(ea), GetDisasm(ea)))
ea = NextHead(ea)
Message("Done!\n")
view rawida-armv7a-cpsr_c.py hosted with ❤ by GitHub
Thus, the instruction becomes:
LOAD:FE80DB4C MSR CPSR_c, #CPSR_MODE_MON OR CPSR_MASK_FIQ OR CPSR_MASK_IRQ ; switch to Monitor mode
This instruction switches the processor to Monitor mode. It also sets CPSR.F and CPSR.I bits to mask FIQ and IRQ exceptions, meaning they cannot be taken.
IV.1.B Setup MVBAR
The Move to Coprocessor from ARM core register instruction (MCR) passes the value of an ARM core register (here R0) to a coprocessor (here CP15).
LOAD:FE80DB50 LDR R0, =monitor_vector_table ; load monitor vector table ptr into R0
LOAD:FE80DB54 MCR p15, 0, R0,c12,c0, 1 ; write R0 to MVBAR
CP15 c12 register is present on an ARMv7-A implementation that includes Security Extensions. This instruction writes R0 value to MVBAR. R0 contains a pointer to Monitor vector table. We will describe this table later.
IV.1.C Initialize Non-Secure world
The function sub_FE80DB88 is called to initialize the Non-Secure world context:
LOAD:FE80DB88 sub_FE80DB88
LOAD:FE80DB88 MRC p15, 0, R1,c1,c0, 0 ; read Secure SCTLR
LOAD:FE80DB8C MOV R0, #SCR_NS OR SCR_FW OR SCR_AW ; #0x31
LOAD:FE80DB90 MCR p15, 0, R0,c1,c1, 0 ; switch to Non-Secure (NS) state
LOAD:FE80DB94 ISB SY
LOAD:FE80DB98 MCR p15, 0, R1,c1,c0, 0 ; write Secure SCTLR value to NS SCTLR
LOAD:FE80DB9C MOV R0, #0
LOAD:FE80DBA0 MCR p15, 2, R0,c0,c0, 0 ; clear CSSELR
LOAD:FE80DBA4 MCR p15, 0, R0,c2,c0, 0 ; clear TTBR0
LOAD:FE80DBA8 MCR p15, 0, R0,c2,c0, 1 ; clear TTBR1
LOAD:FE80DBAC MCR p15, 0, R0,c2,c0, 2 ; clear TTBCR
LOAD:FE80DBB0 MCR p15, 0, R0,c3,c0, 0 ; clear DACR
LOAD:FE80DBB4 MCR p15, 0, R0,c5,c0, 0 ; clear DFSR
LOAD:FE80DBB8 MCR p15, 0, R0,c5,c0, 1 ; clear IFSR
LOAD:FE80DBBC MCR p15, 0, R0,c5,c1, 0 ; clear ADFSR
LOAD:FE80DBC0 MCR p15, 0, R0,c5,c1, 1 ; clear AIFSR
LOAD:FE80DBC4 MCR p15, 0, R0,c6,c0, 0 ; clear DFAR
LOAD:FE80DBC8 MCR p15, 0, R0,c6,c0, 2 ; clear IFAR
LOAD:FE80DBCC MCR p15, 0, R0,c7,c4, 0 ; clear PAR
LOAD:FE80DBD0 MCR p15, 0, R0,c10,c2, 0 ; clear PRRR
LOAD:FE80DBD4 MCR p15, 0, R0,c10,c2, 1 ; clear NMRR
LOAD:FE80DBD8 MCR p15, 0, R0,c10,c4, 0 ; clear "MMUDMTR" ?
LOAD:FE80DBDC MCR p15, 0, R0,c10,c4, 1 ; clear "MMUDCPR" ?
LOAD:FE80DBE0 LDR R1, =dword_FE82B8CC ; load Non-Secure VBAR ptr to R1
LOAD:FE80DBE4 LDR R0, [R1]
LOAD:FE80DBE8 MCR p15, 0, R0,c12,c0, 0 ; write Non-Secure VBAR
LOAD:FE80DBEC MOV R0, #0
LOAD:FE80DBF0 STR R0, [R1] ; clear Non-Secure VBAR ptr
LOAD:FE80DBF4 MCR p15, 0, R0,c13,c0, 0 ; clear FCSEIDR
LOAD:FE80DBF8 MCR p15, 0, R0,c13,c0, 1 ; clear CONTEXTIDR
LOAD:FE80DBFC MCR p15, 0, R0,c13,c0, 2 ; clear TPIDRURW
LOAD:FE80DC00 MCR p15, 0, R0,c13,c0, 3 ; clear TPIDRURO
LOAD:FE80DC04 MCR p15, 0, R0,c13,c0, 4 ; clear TPIDRPRW
LOAD:FE80DC08 MOV R0, #SCR_FW OR SCR_AW ; #0x30
LOAD:FE80DC0C MCR p15, 0, R0,c1,c1, 0 ; switch back to Secure state
LOAD:FE80DC10 ISB SY
LOAD:FE80DC14 BX LR
LOAD:FE80DC14 ; End of function sub_FE80DB88
First, the security state is switched to Non-Secure. Then, the coprocessor registers banked in both security states (ARM Ref. Banked system control registers) are initialized to zero. Finally, the security state is switched back to Secure.
IV.1.D Setup SP register
On ARMv7-A, Multiprocessor Affinity Register (MPIDR) holds the processor identification information. In this register, bits<0:7> are the affinity level 0 (Aff0). This number represents the current CPU id. Here, this id is used to compute the stack address of current CPU, which is then stored into SP register. The stack size for each CPU is 0x200 bytes.
LOAD:FE80DB5C LDR SP, =0xFE82B700
LOAD:FE80DB60 MRC p15, 0, R0,c0,c0, 5 ; write MPIDR value to R0
LOAD:FE80DB64 AND R0, R0, #0xFF ; keep Affinity level 0 : current virtual CPU id
LOAD:FE80DB68 MOV R1, #0x200
LOAD:FE80DB6C MUL R1, R1, R0 ; compute stack offset for current vCPU
LOAD:FE80DB70 SUB SP, SP, R1 ; setup Monitor stack register SP
IV.1.E Route FIQ exceptions to Monitor mode
CP15 c1 register is present on an ARMv7-A implementation that includes Security Extensions. This instruction sets bit<2> (0x4) in Secure Configuration Register (SCR), which means FIQ exceptions are now taken to Monitor mode.
LOAD:FE80DB74 MOV R0, #0b100 ; SCR.FIQ
LOAD:FE80DB78 MCR p15, 0, R0,c1,c1, 0 ; set FIQ flag in SCR register
LOAD:FE80DB7C ISB SY ; flush the pipeline in the processor
We can also notice that bit<0> (SCR.NS : Non-Secure) is not set, meaning current execution state is Secure.
IV.1.F Switch back to Supervisor mode
This instruction switches the processor to Supervisor mode, and sets FIQ & IRQ mask bits.
LOAD:FE80DB80 MSR CPSR_c, #CPSR_MODE_SVC OR CPSR_MASK_FIQ OR CPSR_MASK_IRQ ; switch to Supervisor mode
Monitor mode setup is now complete. Monitor code can then be entered through its exception vector table.
IV.2. Monitor Exception Vector Table
The Monitor exception vector table defines exception vectors to handle exceptions taken to Monitor Mode.
Its structure is described in ARM Ref. (B1-1167) :
The vector table entries
Thank to the Monitor initialization code, we know the address of Nexus 5's Monitor exception vector table:
LOAD:FE80CEE0 monitor_vector_table
LOAD:FE80CEE0 B dead_loop ; not used
LOAD:FE80CEE4 ; ---------------------------------------------------------------------------
LOAD:FE80CEE4 B dead_loop ; not used
LOAD:FE80CEE8 ; ---------------------------------------------------------------------------
LOAD:FE80CEE8 B smc_handler ; Secure Monitor Call
LOAD:FE80CEEC ; ---------------------------------------------------------------------------
LOAD:FE80CEEC B dead_loop ; Prefetch Abort
LOAD:FE80CEF0 ; ---------------------------------------------------------------------------
LOAD:FE80CEF0 B dead_loop ; Data Abort
LOAD:FE80CEF4 ; ---------------------------------------------------------------------------
LOAD:FE80CEF4 B dead_loop ; not used
LOAD:FE80CEF8 ; ---------------------------------------------------------------------------
LOAD:FE80CEF8 B sub_FE80CF24 ; IRQ interrupt
LOAD:FE80CEFC ; ---------------------------------------------------------------------------
LOAD:FE80CEFC B sub_FE80CFB4 ; FIQ interrupt
LOAD:FE80CEFC ; End of function monitor_vector_table
We can see that 3 exception handlers are configured: SMC, FIQ, IRQ. Others are dead loops.
IV.3. Secure Monitor Call handler function
HLOS (non-Secure state) can call the TrustZone API (Secure state) using the SMC instruction to trigger a Secure Monitor Call exception. This exception is taken to the Monitor mode, which switches the processor to Secure Supervisor mode to proceed the call. When called TrustZone function returns, a second SMC exception is triggered, so the processor enters Monitor mode again. Finally, the Monitor mode returns results to the calling function (Non-Secure state).
The Monitor mode acts as a bridge between Non-Secure state and Secure state. It's designed to handle calls initiated from the Non-Secure state only.
The exception vector dedicated to SMC exceptions is a pointer to a function at offset 0x08 in Monitor Exception Vector Table.
In this function, which will be named SMC handler, the very first instruction checks if an exception occurred in Secure or Non-Secure state (When the processor is in Monitor mode, the processor is in Secure state regardless of the value of the SCR.NS bit).
LOAD:FE80D028 smc_handler
LOAD:FE80D028
LOAD:FE80D028 varg_r0 = -0x10
LOAD:FE80D028 varg_r1 = -0xC
LOAD:FE80D028 varg_r2 = -8
LOAD:FE80D028 varg_r3 = -4
LOAD:FE80D028
LOAD:FE80D028 STMFD SP!, {R0-R3}
LOAD:FE80D02C MRC p15, 0, R0,c1,c1, 0 ; read SCR register
LOAD:FE80D030 TST R0, #1 ; test SCR.NS bit
LOAD:FE80D034 BEQ loc_FE80D210 ; jump if SCR.NS==0
When an exception is taken to the Monitor mode, CPSR.{A,I, F} bits are set to 1, meaning Abort, IRQ and FIQ exceptions can no longer be taken.
IV.3.A. Call to Secure World
If SCR.NS bit is set, it means the Non-Secure world wants to call the Secure world. We will now analyze the operations performed by the SMC handler until the exception return to the Secure world.
IV.3.A.a Setup current security state
This first step configures the Secure Configuration Register (SCR). Bits<1:3> (SCR.IRQ || SCR.FIQ || SCR.EA) are set to route IRQ, FIQ, and External Abort exceptions to Monitor mode. But the Non-Secure bit<0> is not set. So, this core will still be in the Secure state if it exits Monitor mode.
LOAD:FE80D038 MOV R0, #SCR_IRQ OR SCR_FIQ OR SCR_EA ; 0b1110
LOAD:FE80D03C MCR p15, 0, R0,c1,c1, 0 ; write SCR with SCR.NS==0
LOAD:FE80D040 ISB SY ; Instruction Synchronization Barrier
LOAD:FE80D040 ; flushes the pipeline in the processor
IV.3.A.b Monitor calls
On a HLOS like Android, SMC exceptions are triggered by the Secure Channel Manager (SCM), implemented in Linux kernel.
A quick look at its source code tells us {R0-R3} registers hold arguments of SMC calls. We also learn that R0 is a bitfield that can be defined by the following macro:
#define SCM_ATOMIC(svc, cmd, n) (((((svc) << 10)|((cmd) & 0x3ff)) << 12) | \
SCM_CLASS_REGISTER | \
SCM_MASK_IRQS | \
(n & 0xf))
With svc the service identifier, cmd the command identifier, and n the argument count of the SMC call.
In SMC handler, R0 value is first shifted right by 12. Based on the SCM_ATOMIC macro definition, resulting R0 value represents a service identifier svc and a command identifier cmd defined as ((svc) << 10)|((cmd) & 0x3ff).
Then R0 value is tested against several immediate values. For each case, a specific function is called if values match.
LOAD:FE80D048 MOV R2, R0,LSR#12 ; extract service & command identifiers
LOAD:FE80D04C MOV R1, #0x402 ; SCM_SVC_BOOT::SCM_CMD_TERMINATE_PC
LOAD:FE80D050 CMP R1, R2
LOAD:FE80D054 LDMEQFD SP!, {R1-R3}
LOAD:FE80D058 BEQ sub_FE80D360
LOAD:FE80D05C MOV R1, #0xC05 ; SCM_SVC_UTIL::CACHE_BUFFER_DUMP_COMMAND_ID
LOAD:FE80D060 CMP R1, R2
LOAD:FE80D064 LDMEQFD SP!, {R1-R3}
LOAD:FE80D068 BEQ sub_FE80D68C
LOAD:FE80D06C MOV R1, #0x404 ; SCM_SVC_BOOT::4
LOAD:FE80D070 CMP R1, R2
LOAD:FE80D074 LDMEQFD SP!, {R1-R3}
LOAD:FE80D078 BEQ sub_FE80D72C
LOAD:FE80D07C MOV R1, #0x1401 ; SCM_SVC_IO::SCM_IO_READ
LOAD:FE80D080 CMP R1, R2
LOAD:FE80D084 LDMEQFD SP!, {R1-R3}
LOAD:FE80D088 BEQ sub_FE80D5AC
LOAD:FE80D08C MOV R1, #0x1402 ; SCM_SVC_IO::SCM_IO_WRITE
LOAD:FE80D090 CMP R1, R2
LOAD:FE80D094 LDMEQFD SP!, {R1-R3}
LOAD:FE80D098 BEQ sub_FE80D5CC
LOAD:FE80D09C MOV R1, #0x3404 ; SCM_SVC_DCVS:CVS_CMD_EVENT
LOAD:FE80D0A0 CMP R1, R2
LOAD:FE80D0A4 LDMEQFD SP!, {R1-R3}
LOAD:FE80D0A8 BEQ sub_FE80D64C
LOAD:FE80D0AC MOV R1, #0x1403 ; SCM_SVC_IO::TZ_RESET_ID
LOAD:FE80D0B0 CMP R1, R2
LOAD:FE80D0B4 LDMEQFD SP!, {R1-R3}
LOAD:FE80D0B8 BEQ sub_FE80D5EC
LOAD:FE80D0BC MOV R1, #0x1404 ; SCM_SVC_IO::TZ_UPDATE_ID
LOAD:FE80D0C0 CMP R1, R2
LOAD:FE80D0C4 LDMEQFD SP!, {R1-R3}
LOAD:FE80D0C8 BEQ sub_FE80D618
LOAD:FE80D0CC MOV R1, #0x2401 ; SCM_SVC_PWR::SCM_IO_DISABLE_PMIC_ARBITER
LOAD:FE80D0D0 CMP R1, R2
LOAD:FE80D0D4 LDMEQFD SP!, {R1-R3}
LOAD:FE80D0D8 BEQ sub_FE80D74C
As Linux kernel itself initiates a lot of SMC calls, we explore Linux sources to enumerate service and command identifiers passed to SMC calls. Thereby, we will get more information on corresponding functions without reversing them.
Immediate value Service ID (imm>>10) Command ID (imm&0x3ff) Function description
0x402 SCM_SVC_BOOT SCM_CMD_TERMINATE_PC Put current core in low power state
0xC05 SCM_SVC_UTIL CACHE_BUFFER_DUMP_COMMAND_ID Dump the L1 and L2 caches on panic
0x404 SCM_SVC_BOOT 4 Dummy function, returns to Non-Secure world
0x1401 SCM_SVC_IO SCM_IO_READ Dummy function, returns to Non-Secure world
0x1402 SCM_SVC_IO SCM_IO_WRITE Dummy function, returns to Non-Secure world
0x3404 SCM_SVC_DCVS DCVS_CMD_EVENT Handle some Dynamic Clock and Voltage Scaling (DCVS) See also event definitions
0x1403 SCM_SVC_IO TZ_RESET_ID Related to GPU power management
0x1404 SCM_SVC_IO TZ_UPDATE_ID Related to GPU power management
0x2401 SCM_SVC_PWR SCM_IO_DISABLE_PMIC_ARBITER "Force the SPMI PMIC arbiter to shutdown so that no more SPMI transactions are sent from the MSM to the PMIC."
All these functions have the same epilogue:
LOAD:FE80D738 MOV R3, #SCR_NS OR SCR_FIQ OR SCR_AW ; 0b100101
LOAD:FE80D73C MCR p15, 0, R3,c1,c1, 0 ; write SCR : switch to Non-Secure state
LOAD:FE80D740 ISB SY
LOAD:FE80D744 MOV R3, #0 ; clear R3 to avoid leak
LOAD:FE80D748 MOVS PC, LR ; restore Non-Secure PC & CPSR from LR_mon & SPSR_mon
These instructions switch the processor to Non-Secure state and restore PC & CPSR to perform an exception return.
So SMC calls associated with these specific command/service IDs are kind of "Monitor calls", entirely handled in Monitor mode.
But if R0 value does not match these IDs, the execution continues in Monitor mode.
IV.3.A.c TrustZone lock
If the call has not been handled yet, Monitor code tries to acquire a lock to ensure that only one core at a time enters in TrustZone.
First, current CPU id is retrieved from MPIDR. Then, this value is incremented (because 0 means not locked) and used as lock value.
LOAD:FE80D0E0 LDR R1, =tz_lock
LOAD:FE80D0E4 MRC p15, 0, R2,c0,c0, 5 ; read MPIDR register
LOAD:FE80D0E8 AND R2, R2, #0xFF ; extract Aff0 from MPIDR
LOAD:FE80D0EC ADD R2, R2, #1
LOAD:FE80D0F0
LOAD:FE80D0F0 loc_FE80D0F0 ; CODE XREF: smc_handler+D8j
LOAD:FE80D0F0 LDREX R0, [R1] ; read current tz_lock value
LOAD:FE80D0F4 CMP R0, #0 ; test if TrustZone is locked
LOAD:FE80D0F8 STREXEQ R0, R2, [R1] ; if not locked, try to lock TrustZone
LOAD:FE80D0FC CMPEQ R0, #0 ; test if TrustZone is now locked
LOAD:FE80D100 BNE loc_FE80D0F0 ; retry if TrustZone is still not locked
LOAD:FE80D104 DMB SY ; Data Memory Barrier acts as a memory barrier
Then, it tries to acquire the TrustZone lock. This implementation is very similar to the example provided in ARM Ref. (D7.3.1 Acquiring a lock).
It relies on synchronization primitives (LDREX/STREX) to support exclusive accesses to memory shared between cores.
Once the lock is acquired, the current core is the only one running in TrustZone, and the execution can continue.
IV.3.A.d Pre-exception status
LR_mon and SPSR_mon are both banked registers. Their values are generated by the exception entry. LR_mon contains the return address in Non-Secure world (right after the SMC instruction). The purpose of SPSR_mon is to record the pre-exception value of the CPSR.
LOAD:FE80D108 LDR R0, =NS_core_status ; secure area to store Non-Secure (NS) status
LOAD:FE80D10C MOV R1, LR ; read NS return address (LR_mon)
LOAD:FE80D110 MRS R2, SPSR ; read NS CPSR (SPSR_mon)
LOAD:FE80D114 STMIA R0, {R1,R2} ; write LR_mon & SPSR_mon
These two registers are saved in Secure memory to be restored later on exception return.
IV.3.A.e IRQ interruption flag
Then a DWORD at a static address is unconditionally cleared:
LOAD:FE80D118 LDR R1, =tz_irq_interrupted
LOAD:FE80D11C MOV R0, #0
LOAD:FE80D120 STR R0, [R1] ; clear tz_irq_interrupted value
By looking at cross-references, we notice this DWORD is set to 1 in the IRQ handler of Monitor mode. But in both handlers (SMC & IRQ), when an exception returns to the Non-Secure world, the returned value (in R0) is set to 1 if this DWORD is not null.
Futhermore, we can have a look at how SCM interprets the value returned by a SMC call:
#define SCM_INTERRUPTED 1
do {
asm volatile(
__asmeq("%0", "r0")
__asmeq("%1", "r0")
__asmeq("%2", "r1")
__asmeq("%3", "r2")
#ifdef REQUIRES_SEC
".arch_extension sec\n"
#endif
"smc #0 @ switch to secure world\n"
: "=r" (r0)
: "r" (r0), "r" (r1), "r" (r2)
: "r3");
} while (r0 == SCM_INTERRUPTED);
SCM will reiterate each SMC call while the returned value is 1.
We can deduce that this DWORD indicates if the exception return is due to an IRQ interrupt. TrustZone Whitepaper (3.3.3 Secure interrupts) says ARM recommends the use of IRQ as a Normal world interrupt source. That's why IRQ interrupts are handled in the Normal world.
IV.3.A.f Configure Secure world MMU
Next block of instructions modifies the translation table of Secure MMU (ARM Ref. B3.1 About the VMSA) if two conditions are met:
--

Wouldn't it be easier to provide the link?
http://www.fredericb.info/2014/12/analysis-of-nexus-5-monitor-mode.html

Develop Bugs

welcome