Re: [PATCH -tip v5 06/10] kprobes/x86: Cleanup save/restore registers

Masami Hiramatsu
2009-11-24T15:37:49Z

Frederic Weisbecker wrote:
> On Mon, Nov 23, 2009 at 06:22:04PM -0500, Masami Hiramatsu wrote:
>> +#ifdef CONFIG_X86_64
>> +#define SAVE_REGS_STRING \
>> + /* Skip cs, ip, orig_ax. */ \
>> + " subq $24, %rsp\n" \
>> + " pushq %rdi\n" \
>> + " pushq %rsi\n" \
>> + " pushq %rdx\n" \
>> + " pushq %rcx\n" \
>> + " pushq %rax\n" \
>> + " pushq %r8\n" \
>> + " pushq %r9\n" \
>> + " pushq %r10\n" \
>> + " pushq %r11\n" \
>> + " pushq %rbx\n" \
>> + " pushq %rbp\n" \
>> + " pushq %r12\n" \
>> + " pushq %r13\n" \
>> + " pushq %r14\n" \
>> + " pushq %r15\n"
>> +#define RESTORE_REGS_STRING \
>> + " popq %r15\n" \
>> + " popq %r14\n" \
>> + " popq %r13\n" \
>> + " popq %r12\n" \
>> + " popq %rbp\n" \
>> + " popq %rbx\n" \
>> + " popq %r11\n" \
>> + " popq %r10\n" \
>> + " popq %r9\n" \
>> + " popq %r8\n" \
>> + " popq %rax\n" \
>> + " popq %rcx\n" \
>> + " popq %rdx\n" \
>> + " popq %rsi\n" \
>> + " popq %rdi\n" \
>
>
> BTW, do you really need to push/pop every registers
> before/after calling a probe handler?

Yes, in both cases (kretprobe/optprpbe) it needs to
emulate kprobes behavior. kprobes can be used as
fault injection, it should pop pt_regs.

> Is it possible to only save/restore the scratch ones?

Hmm, what code did you mean?

Thank you,