From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

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>
---

 arch/i386/kernel/kprobes.c |   22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff -puN arch/i386/kernel/kprobes.c~fix-kretprobe-booster-to-save-regs-and-set-status arch/i386/kernel/kprobes.c
--- a/arch/i386/kernel/kprobes.c~fix-kretprobe-booster-to-save-regs-and-set-status
+++ a/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_hand
 	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_hand
 
 		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;
 		}
_