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[PATCH] Kprobes: Incorrect handling of probes on ret/lret instruction
- From: Prasanna S Panchamukhi <prasanna at in dot ibm dot com>
- To: SystemTAP <systemtap at sources dot redhat dot com>, akpm at osdl dot org, Andi Kleen <ak at muc dot de>, davem at davemloft dot net, ananth at in dot ibm dot com, linux-kernel at vger dot kernel dot org
- Date: Fri, 1 Apr 2005 14:07:10 +0530
- Subject: [PATCH] Kprobes: Incorrect handling of probes on ret/lret instruction
- Reply-to: prasanna at in dot ibm dot com
Hi,
Kprobes could not handle the insertion of a probe on the ret/lret instruction
and used to oops after single stepping since kprobes was modifying eip/rip
incorrectly. Adjustment of eip/rip is not required after single stepping in
case of ret/lret instruction, because eip/rip points to the correct location
after execution of the ret/lret instruction. This patch fixes the above problem.
Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
---
---
linux-2.6.12-rc1-prasanna/arch/i386/kernel/kprobes.c | 7 +++++++
linux-2.6.12-rc1-prasanna/arch/x86_64/kernel/kprobes.c | 7 +++++++
2 files changed, 14 insertions(+)
diff -puN arch/i386/kernel/kprobes.c~kprobes-ret-address-fix arch/i386/kernel/kprobes.c
--- linux-2.6.12-rc1/arch/i386/kernel/kprobes.c~kprobes-ret-address-fix 2005-03-31 14:32:56.000000000 +0530
+++ linux-2.6.12-rc1-prasanna/arch/i386/kernel/kprobes.c 2005-03-31 14:37:24.000000000 +0530
@@ -218,6 +218,13 @@ 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;
case 0xe8: /* call relative - Fix return addr */
*tos = orig_eip + (*tos - copy_eip);
break;
diff -puN arch/x86_64/kernel/kprobes.c~kprobes-ret-address-fix arch/x86_64/kernel/kprobes.c
--- linux-2.6.12-rc1/arch/x86_64/kernel/kprobes.c~kprobes-ret-address-fix 2005-03-31 14:33:31.000000000 +0530
+++ linux-2.6.12-rc1-prasanna/arch/x86_64/kernel/kprobes.c 2005-03-31 14:37:08.000000000 +0530
@@ -231,6 +231,13 @@ static void resume_execution(struct kpro
*tos &= ~(TF_MASK | IF_MASK);
*tos |= kprobe_old_rflags;
break;
+ case 0xc3: /* ret/lret */
+ case 0xcb:
+ case 0xc2:
+ case 0xca:
+ regs->eflags &= ~TF_MASK;
+ /* rip is already adjusted, no more changes required*/
+ return;
case 0xe8: /* call relative - Fix return addr */
*tos = orig_rip + (*tos - copy_rip);
break;
_
Thanks
Prasanna
--
Prasanna S Panchamukhi
Linux Technology Center
India Software Labs, IBM Bangalore
Ph: 91-80-25044636
<prasanna@in.ibm.com>