Hi Jean,
On Mon, Mar 03, 2014 at 09:53:21AM +0000, Jean Pihet wrote:
> Introducing perf_regs_load function, which is going
> to be used for dwarf unwind test in following patches.
>
> It takes single argument as a pointer to the regs dump
> buffer and populates it with current registers values.
[...]
> diff --git a/tools/perf/arch/arm/tests/regs_load.S
> b/tools/perf/arch/arm/tests/regs_load.S
> new file mode 100644
> index 0000000..241c6df
> --- /dev/null
> +++ b/tools/perf/arch/arm/tests/regs_load.S
> @@ -0,0 +1,51 @@
> +#include <linux/linkage.h>
> +
> +#define R0 0x00
> +#define R1 0x08
Why are you using a 64-bit stride for 32-bit registers? (which prevents you
from using stm later on).
> +.text
> +.type perf_regs_load,%function
> +ENTRY(perf_regs_load)
> + push {r1}
Do you only push r1 here so that you can do the stack arithmetic later? That
doesn't make sense to me -- can't you str sp directly?
> + str r0, [r0, #R0]
> + str r1, [r0, #R1]
> + str r2, [r0, #R2]
> + str r3, [r0, #R3]
> + str r4, [r0, #R4]
> + str r5, [r0, #R5]
> + str r6, [r0, #R6]
> + str r7, [r0, #R7]
> + str r8, [r0, #R8]
> + str r9, [r0, #R9]
> + str sl, [r0, #SL]
> + str fp, [r0, #FP]
> + str ip, [r0, #IP]
> + add r1, sp, #4 @ Retrieve and save sp at entry time
> + str r1, [r0, #SP]
> + str lr, [r0, #LR]
> + str lr, [r0, #PC] @ Save caller PC
This isn't necessarily the `caller PC' (depending on how you define it).
It's the return address, which is probably (but not always) the instruction
following the branch to this function.
Will
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