Problem with GDB when debugging IRQ handlers

[Catalin Marinas]

On Tue, Jun 28, 2011 at 11:26:28PM +0100, Dmitry Eremin-Solenikov wrote:
> On 6/28/11, Catalin Marinas <catalin.marinas at 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.

-- 
Catalin