[PATCH] kretprobe: fix kretprobe-booster to save regs and set status

There are two bugs in the kretprobe-booster.

1) It doesn't make room for gs registers.

2) It doesn't change status of the current kprobe.  This status will
   effect the fault handling.

This patch fixes these bugs and, additionally, saves skipped registers for
compatibility with the original kretprobe.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index d98e44b16fe20fa1edbda6d0246bc95b3a49cede..fc79e1e859c498a9d640ba40fcff7494fe6110b6 100644 (file)
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -361,8 +361,11 @@ no_kprobe:
        asm volatile ( ".global kretprobe_trampoline\n"
                        "kretprobe_trampoline: \n"
                        "       pushf\n"
-                       /* skip cs, eip, orig_eax, es, ds */
-                       "       subl $20, %esp\n"
+                       /* skip cs, eip, orig_eax */
+                       "       subl $12, %esp\n"
+                       "       pushl %gs\n"
+                       "       pushl %ds\n"
+                       "       pushl %es\n"
                        "       pushl %eax\n"
                        "       pushl %ebp\n"
                        "       pushl %edi\n"
@@ -373,10 +376,10 @@ no_kprobe:
                        "       movl %esp, %eax\n"
                        "       call trampoline_handler\n"
                        /* move eflags to cs */
-                       "       movl 48(%esp), %edx\n"
-                       "       movl %edx, 44(%esp)\n"
+                       "       movl 52(%esp), %edx\n"
+                       "       movl %edx, 48(%esp)\n"
                        /* save true return address on eflags */
-                       "       movl %eax, 48(%esp)\n"
+                       "       movl %eax, 52(%esp)\n"
                        "       popl %ebx\n"
                        "       popl %ecx\n"
                        "       popl %edx\n"
@@ -384,8 +387,8 @@ no_kprobe:
                        "       popl %edi\n"
                        "       popl %ebp\n"
                        "       popl %eax\n"
-                       /* skip eip, orig_eax, es, ds */
-                       "       addl $16, %esp\n"
+                       /* skip eip, orig_eax, es, ds, gs */
+                       "       addl $20, %esp\n"
                        "       popf\n"
                        "       ret\n");
 }
@@ -404,6 +407,10 @@ fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
        INIT_HLIST_HEAD(&empty_rp);
        spin_lock_irqsave(&kretprobe_lock, flags);
        head = kretprobe_inst_table_head(current);
+       /* fixup registers */
+       regs->xcs = __KERNEL_CS;
+       regs->eip = trampoline_address;
+       regs->orig_eax = 0xffffffff;
 
        /*
         * It is possible to have multiple instances associated with a given
@@ -425,6 +432,7 @@ fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
 
                if (ri->rp && ri->rp->handler){
                        __get_cpu_var(current_kprobe) = &ri->rp->kp;
+                       get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
                        ri->rp->handler(ri, regs);
                        __get_cpu_var(current_kprobe) = NULL;
                }