Research on Qualcomm platform debugging (-)

12.1680-v6107-20.rev_a_debug_troubleshoot.pdf

 

When the function is called, The R0-R3 passes four parameters, the rest are saved through the stack, and the parameters are imported from the right to the left order into the stack.

R13 is the stack pointer Stack pointer (SP). It does not need to be used for other purposes and always points to the current position in the stack. When context switch is enabled, Rex uses SP to switch the execution of different tasks (points SP to the stack of different tasks ).

 

R14 generally saves the return address.

PC R15 saves the next command.

 

BL jump command: before the jump, the current content of the PC will be saved in register R14, so you can re-load the content of R14 to the PC, to return the execution of the command after the jump command.

 

BL label: when the program jumps to the label unconditionally, it saves the current Pc value to R14.

 

The R13 (SP) address is 0x140218fc.

Enter the command: D. Dump ui_stack/byte to view the UI stack, as shown in.

See the following value, now push {r1-r7, R14} has been executed:

Address 0x140218fc value 0x1411fc78-contents of R1 <-SP points here

0x14021900 0x00000001-contents of R2

0x14021904 0x00142be3-contents of r3

0x14021908 0x00000000-contents of r4

0x1402191c 0x1411f438-contents of R5

0x14021920 0x14120338-contents of R6

0x14021924 0x14120358-contents of r7

0x14021928 0x00142beb-R14-return address

The value of R14 returns the next command and runs uiuasmsn_init ().

 

FIQ: Fast interrupt, which has a higher priority than IRQ interrupt.

FIQ interrupt vector: Fast interrupt request vector table. When an exception orInterruptedWhen this occurs, the processor sets the PC as a special memory address (faster RAM memory ). This address is called the interrupt vector table. The entry to the interrupt vector table is the entry to the interrupt and abnormal branches ..

 

Intlock () and intfree () in Rex can control the Enable of FIQ and IRQ interruptions.

FIQ interruption occurs every 1.25 mS, so the suspension lock time cannot be longer than Ms.

 

Tasklock protects the current task activity status from being replaced by other tasks, but does not protect it from being interrupted.

 

Use intlock () and intfree:

Before an interruption is locked, intlock will save the status of the current IRQ/FIQ identifier. This value may be 0 (the interrupt is enabled, before the lock), or not 0 (the interrupt is not enabled before the lock ).

 

# Define intlock () {DWORD sav = rex_int_lock ();

# Define intfree () if (! Sav) (void) rex_int_free ();}