Hi Harvey,
Harvey Harrison wrote:
> Fold some small ifdefs into a helper function.
>
> Signed-off-by: Harvey Harrison <[email protected]>
> ---
> Masami, Ingo, I had this left in some unsent kprobes unification
> work. Depends on your tastes, but does reduce ifdefs and is a bit
> better about self-documenting the REX prefix on X86_64.
Basically, I think it is good idea.
Could you use a macro same as the stack_addr() macro, like as below?
#defile is_REX_prefix(insn) ((insn & 0xf0) == 0x40))
This is just a bit checker, so I think a macro is better to do that.
> If I find places that could also use this I'll try to find a suitable
> header any stick a static inline there instead. Otherwise static to
> kprobes.c is probably more appropriate for now.
>
> arch/x86/kernel/kprobes.c | 27 +++++++++++++++++++--------
> 1 files changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
> index 4e33329..b1804e4 100644
> --- a/arch/x86/kernel/kprobes.c
> +++ b/arch/x86/kernel/kprobes.c
> @@ -171,6 +171,19 @@ static void __kprobes set_jmp_op(void *from, void *to)
> }
>
> /*
> + * Check for the REX prefix which can only exist on X86_64
> + * X86_32 always returns 0
> + */
> +static int __kprobes is_REX_prefix(kprobe_opcode_t *insn)
> +{
> +#ifdef CONFIG_X86_64
> + if ((*insn & 0xf0) == 0x40)
> + return 1;
> +#endif
> + return 0;
> +}
> +
> +/*
> * Returns non-zero if opcode is boostable.
> * RIP relative instructions are adjusted at copying time in 64 bits mode
> */
> @@ -239,14 +252,14 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
> case 0x9d: /* popf/popfd */
> return 1;
> }
> -#ifdef CONFIG_X86_64
> +
> /*
> - * on 64 bit x86, 0x40-0x4f are prefixes so we need to look
> + * on X86_64, 0x40-0x4f are REX prefixes so we need to look
> * at the next byte instead.. but of course not recurse infinitely
> */
> - if (*insn >= 0x40 && *insn <= 0x4f)
> + if (is_REX_prefix(insn))
> return is_IF_modifier(++insn);
> -#endif
> +
> return 0;
> }
>
> @@ -284,7 +297,7 @@ static void __kprobes fix_riprel(struct kprobe *p)
> }
>
> /* Skip REX instruction prefix. */
> - if ((*insn & 0xf0) == 0x40)
> + if (is_REX_prefix(insn))
> ++insn;
>
> if (*insn == 0x0f) {
> @@ -748,11 +761,9 @@ static void __kprobes resume_execution(struct kprobe *p,
> unsigned long orig_ip = (unsigned long)p->addr;
> kprobe_opcode_t *insn = p->ainsn.insn;
>
> -#ifdef CONFIG_X86_64
> /*skip the REX prefix*/
> - if (*insn >= 0x40 && *insn <= 0x4f)
> + if (is_REX_prefix(insn))
> insn++;
> -#endif
>
> regs->flags &= ~X86_EFLAGS_TF;
> switch (*insn) {
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: [email protected], [email protected]
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