On Fri, 2009-04-03 at 12:02 -0400, Masami Hiramatsu wrote:
> Ensure safeness of inserting kprobes by checking whether the specified
> address is at the first byte of a instruction. This is done by decoding
> probed function from its head to the probe point.
>
> changes from v4:
> - change a comment according to Ananth's suggestion.
>
> Signed-off-by: Masami Hiramatsu <[email protected]>
> Cc: Ananth N Mavinakayanahalli <[email protected]>
> Cc: Jim Keniston <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> ---
>
> arch/x86/kernel/kprobes.c | 51
> +++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 51 insertions(+), 0 deletions(-)
>
>
> diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
...
>
> +/* Recover original instruction */
/* Recover the probed instruction at addr for further analysis. */
See below.
> +static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long
> addr)
> +{
> + struct kprobe *kp;
> + kp = get_kprobe((void *)addr);
> + if (!kp)
> + return -EINVAL;
> +
> + /* Don't use p->ainsn.insn; which will be modified by fix_riprel */
fix_riprel doesn't affect the instruction's length, which is what
concerns this patch. But we want this function to be useful for
unforeseen uses as well, so I like the code you have. Just consider the
suggested comment changes.
/*
* Don't use p->ainsn.insn, which could be modified -- e.g.,
* by fix_riprel().
*/
> + memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
> + buf[0] = kp->opcode;
> + return 0;
> +}
Jim Keniston
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