x86: jprobe bugfix

jprobe for x86-64 may cause kernel page fault when the jprobe_return()
is called from incorrect function.

- Use jprobe_saved_regs instead getting it from stack.
  (Especially on x86-64, it may get incorrect data, because
   pt_regs can not be get by using container_of(rsp))
- Change the type of stack pointer to unsigned long *.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/kprobes_32.c

@@ -727,9 +727,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 
 	if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
 		if (&regs->esp != kcb->jprobe_saved_esp) {
-			struct pt_regs *saved_regs =
-			    container_of(kcb->jprobe_saved_esp,
-					    struct pt_regs, esp);
+			struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
 			printk("current esp %p does not match saved esp %p\n",
 			       &regs->esp, kcb->jprobe_saved_esp);
 			printk("Saved registers for jprobe %p\n", jp);

arch/x86/kernel/kprobes_64.c

@@ -716,10 +716,8 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 	struct jprobe *jp = container_of(p, struct jprobe, kp);
 
 	if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
-		if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
-			struct pt_regs *saved_regs =
-			    container_of(kcb->jprobe_saved_rsp,
-					    struct pt_regs, rsp);
+		if ((unsigned long *)regs->rsp != kcb->jprobe_saved_rsp) {
+			struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
 			printk("current rsp %p does not match saved rsp %p\n",
 			       (long *)regs->rsp, kcb->jprobe_saved_rsp);
 			printk("Saved registers for jprobe %p\n", jp);

include/asm-x86/kprobes_32.h

@@ -73,7 +73,7 @@ struct kprobe_ctlblk {
 	unsigned long kprobe_status;
 	unsigned long kprobe_old_eflags;
 	unsigned long kprobe_saved_eflags;
-	long *jprobe_saved_esp;
+	unsigned long *jprobe_saved_esp;
 	struct pt_regs jprobe_saved_regs;
 	kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
 	struct prev_kprobe prev_kprobe;

include/asm-x86/kprobes_64.h

@@ -66,7 +66,7 @@ struct kprobe_ctlblk {
 	unsigned long kprobe_status;
 	unsigned long kprobe_old_rflags;
 	unsigned long kprobe_saved_rflags;
-	long *jprobe_saved_rsp;
+	unsigned long *jprobe_saved_rsp;
 	struct pt_regs jprobe_saved_regs;
 	kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
 	struct prev_kprobe prev_kprobe;