Re: Problem with GDB when debugging IRQ handlers

[Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>]

On 6/29/11, Catalin Marinas <catalin.marinas@arm.com> wrote:
> On Tue, Jun 28, 2011 at 11:26:28PM +0100, Dmitry Eremin-Solenikov wrote:
>> On 6/28/11, Catalin Marinas <catalin.marinas@arm.com> wrote:
>> > On Tue, Jun 28, 2011 at 04:45:52PM +0100, Dmitry Eremin-Solenikov wrote:
>> >>  	.macro	svc_entry, stack_hole=0
>> >>   UNWIND(.fnstart		)
>> >> +	.cfi_startproc
>> >>   UNWIND(.save {r0 - pc}		)
>> >>  	sub	sp, sp, #(S_FRAME_SIZE + \stack_hole - 4)
>> >>  #ifdef CONFIG_THUMB2_KERNEL
>> >> @@ -146,6 +148,24 @@ ENDPROC(__und_invalid)
>> >>  	@  r4 - orig_r0 (see pt_regs definition in ptrace.h)
>> >>  	@
>> >>  	stmia	r5, {r0 - r4}
>> >> +	.cfi_def_cfa_offset S_PC + 4
>> >> +	.cfi_offset 14, -4
>> >> +#define	CFI_REG_OFF(r) .cfi_offset r, (r - 16) * 4
>> >> +	CFI_REG_OFF(13)
>> >> +	CFI_REG_OFF(12)
>> >> +	CFI_REG_OFF(11)
>> >> +	CFI_REG_OFF(10)
>> >> +	CFI_REG_OFF(9)
>> >> +	CFI_REG_OFF(8)
>> >> +	CFI_REG_OFF(7)
>> >> +	CFI_REG_OFF(6)
>> >> +	CFI_REG_OFF(5)
>> >> +	CFI_REG_OFF(4)
>> >> +	CFI_REG_OFF(3)
>> >> +	CFI_REG_OFF(2)
>> >> +	CFI_REG_OFF(1)
>> >> +	CFI_REG_OFF(0)
>> >> +#undef CFI_REG_OFF
>> >>  	.endm
>> >
>> > Do we need all the registers in here for gdb stack unwinding? In general
>> > we would only need LR, SP and FP.
>>
>> CFI info isn't only related to stack unwinding. IIUC (I'll have to run
>> more experiments) these instrutions will help me to get correct
>> variables/arguments values in the before-exception stack frames.
>
> OK, in this case we may need to add some annotations. You could actually
> generate a .s file from and existing C one (including -g) and see what
> .cfi directives it generates.

Yes, that actually gave me some ideas. Unfortunately entry*.S files are
a bit ... uncommon, so there are nearly no 1-1 cases. BTW: It seems x86
has .cfi annotations connected to most if not all assembler commands.
I think this is a bit too much, but you got the idea.

-- 
With best wishes
Dmitry