This is the mail archive of the
systemtap@sources.redhat.com
mailing list for the systemtap project.
Re: kprobes problem
- From: Maneesh Soni <maneesh at in dot ibm dot com>
- To: Prasanna S Panchamukhi <prasanna at in dot ibm dot com>
- Cc: Baruch Even <baruch at ev-en dot org>, systemtap at sources dot redhat dot com, varap at us dot ibm dot com
- Date: Tue, 15 Mar 2005 09:44:03 +0530
- Subject: Re: kprobes problem
- References: <20050314163142.GD31327@in.ibm.com>
- Reply-to: maneesh at in dot ibm dot com
On Mon, Mar 14, 2005 at 10:01:42PM +0530, Prasanna S Panchamukhi wrote:
> Hi Baruch,
>
> Thanks for pointing it out.
> Yes, kprobes could not handle probes on ret/lret instruction.
> The instruction pointer modification in case of ret/lret
> instrcution is not required.
> The below patch should fix the problem. This patch is for i386
> achitecture and soon will be ported to other architectures.
>
> Please let me know if you have any issues.
>
> Thanks
> Prasanna
>
>
> Kprobes could not handle the insertion of a probe on a ret/lret instruction.
> This patch fixes the above bug by avoiding adjustment of instruction pointer,
>
> Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
>
>
> ---
>
> linux-2.6.11-rc5-prasanna/arch/i386/kernel/kprobes.c | 8 ++++++++
> 1 files changed, 8 insertions(+)
>
> diff -puN arch/i386/kernel/kprobes.c~kprobes-ret-address-fix arch/i386/kernel/kprobes.c
> --- linux-2.6.11-rc5/arch/i386/kernel/kprobes.c~kprobes-ret-address-fix 2005-03-14 21:27:34.000000000 +0530
> +++ linux-2.6.11-rc5-prasanna/arch/i386/kernel/kprobes.c 2005-03-14 21:48:39.000000000 +0530
> @@ -208,6 +208,14 @@ static void resume_execution(struct kpro
> *tos &= ~(TF_MASK | IF_MASK);
> *tos |= kprobe_old_eflags;
> break;
> + case 0xc3: /* ret/lret */
> + case 0xcb:
> + case 0xc2:
> + case 0xca:
> + regs->eflags &= ~TF_MASK;
> + /* eip is already adjusted, no more changes required*/
> + return;
> + break;
^^^^^^^^^^^^^^^^^^^
why "break" after "return"
> case 0xe8: /* call relative - Fix return addr */
> *tos = orig_eip + (*tos - copy_eip);
> break;
>
> _
> --
>
> Prasanna S Panchamukhi
> Linux Technology Center
> India Software Labs, IBM Bangalore
> Ph: 91-80-25044636
> <prasanna@in.ibm.com>
--
Maneesh Soni
Linux Technology Center,
IBM India Software Labs,
Bangalore, India
email: maneesh@in.ibm.com
Phone: 91-80-25044990