[PATCH] Kprobes: Incorrect handling of probes on ret/lret instruction

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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 14 insertions, 0 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 671681659243..59ff9b455069 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -217,6 +217,13 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs)
                 *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 --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 4f2a852299b6..f77f8a0ff187 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -355,6 +355,13 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs)
                 *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;