Re: [PATCH][kprobe]disallow kprobes on emulate_step function

[Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>]

On Tue, Oct 31, 2006 at 05:13:19PM +0800, Gui,Jian wrote:
> Probing on emulate_step function will crash 2.6.18.1 when it is
> triggered. This problem is powerpc dependent.
> 
> When kprobe is triggered, emulate_step is on its kernel path and
> will cause recursive kprobe fault. This patch can disallow
> kprobes on emulate_step function.

Looks good, but not complete :-) Even branch_taken() needs to be
__kprobes as emulate_step() calls it.

Please add that and feel free to post the patch to linuxppc-dev
for upstream inclusion.

Ananth

> 
> 
> diff -Nur linux-2.6.18.1/arch/powerpc/lib/sstep.c 
> new/arch/powerpc/lib/sstep.c
> --- linux-2.6.18.1/arch/powerpc/lib/sstep.c     2006-10-13 
> 23:34:03.000000000 -0400
> +++ new/arch/powerpc/lib/sstep.c        2006-10-31 06:14:44.000000000 
> -0500
> @@ -9,6 +9,7 @@
>   * 2 of the License, or (at your option) any later version.
>   */
>  #include <linux/kernel.h>
> +#include <linux/kprobes.h>
>  #include <linux/ptrace.h>
>  #include <asm/sstep.h>
>  #include <asm/processor.h>
> @@ -51,7 +52,7 @@
>   * or -1 if the instruction is one that should not be stepped,
>   * such as an rfid, or a mtmsrd that would clear MSR_RI.
>   */
> -int emulate_step(struct pt_regs *regs, unsigned int instr)
> +int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
>  {
>         unsigned int opcode, rd;
>         unsigned long int imm;