[PATCH 1/4] x86: fix jprobe_saved_sp handling

[Harvey Harrison]

This patch fixes a bug of jprobe and cleans up. jprobe for x86-64
can cause kernel page fault when the jprobe_return() is called from
incorrect function. Anyway, that path finally invokes BUG() macro,
so this is not so serious.

Based on patch from Masami Hiramatsu <[EMAIL PROTECTED]>

- 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: Harvey Harrison <[EMAIL PROTECTED]>
---
 arch/x86/kernel/kprobes.c |    8 ++------
 include/asm-x86/kprobes.h |    2 +-
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index e5b7d07..9130c01 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -1022,16 +1022,12 @@ int __kprobes longjmp_break_handler(struct kprobe *p, 
struct pt_regs *regs)
        if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) 
{
 #ifdef CONFIG_X86_32
                if (&regs->sp != kcb->jprobe_saved_sp) {
-                       struct pt_regs *saved_regs =
-                           container_of(kcb->jprobe_saved_sp,
-                                           struct pt_regs, sp);
+                       struct pt_regs *saved_regs = &kcb->jprobe_saved_sp;
                        printk("current sp %p does not match saved sp %p\n",
                               &regs->sp, kcb->jprobe_saved_sp);
 #else
                if ((long *)regs->sp != kcb->jprobe_saved_sp) {
-                       struct pt_regs *saved_regs =
-                           container_of(kcb->jprobe_saved_sp,
-                                           struct pt_regs, sp);
+                       struct pt_regs *saved_regs = &kcb->jprobe_saved_sp;
                        printk("current sp %p does not match saved sp %p\n",
                               (long *)regs->sp, kcb->jprobe_saved_sp);
 #endif
diff --git a/include/asm-x86/kprobes.h b/include/asm-x86/kprobes.h
index e348ed6..7319c62 100644
--- a/include/asm-x86/kprobes.h
+++ b/include/asm-x86/kprobes.h
@@ -79,7 +79,7 @@ struct kprobe_ctlblk {
        unsigned long kprobe_status;
        unsigned long kprobe_old_flags;
        unsigned long kprobe_saved_flags;
-       long *jprobe_saved_sp;
+       unsigned long *jprobe_saved_sp;
        struct pt_regs jprobe_saved_regs;
        kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
        struct prev_kprobe prev_kprobe;
-- 
1.5.4.rc0.1083.gf568


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