[PATCH] kprobe handler: discard user space trap

Currently kprobe handler traps only happen in kernel space, so function
kprobe_exceptions_notify should skip traps which happen in user space.
This patch modifies this, and it is based on 2.6.16-rc4.

Signed-off-by: bibo mao <bibo.mao@intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>
Cc: <hiramatu@sdl.hitachi.co.jp>
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>

1 files changed, 6 insertions, 13 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index acdcc640a72a..df1b346d36ff 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -203,13 +203,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
         struct kprobe *p;
         int ret = 0;
-        kprobe_opcode_t *addr = NULL;
-        unsigned long *lp;
+        kprobe_opcode_t *addr;
         struct kprobe_ctlblk *kcb;
 #ifdef CONFIG_PREEMPT
         unsigned pre_preempt_count = preempt_count();
 #endif /* CONFIG_PREEMPT */
 
+        addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
+
         /*
          * We don't want to be preempted for the entire
          * duration of kprobe processing
@@ -217,17 +218,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
         preempt_disable();
         kcb = get_kprobe_ctlblk();
 
-        /* Check if the application is using LDT entry for its code segment and
-         * calculate the address by reading the base address from the LDT entry.
-         */
-        if ((regs->xcs & 4) && (current->mm)) {
-                lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
-                                        + (char *) current->mm->context.ldt);
-                addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
-                                                sizeof(kprobe_opcode_t));
-        } else {
-                addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
-        }
         /* Check we're not actually recursing */
         if (kprobe_running()) {
                 p = get_kprobe(addr);
@@ -579,6 +569,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         struct die_args *args = (struct die_args *)data;
         int ret = NOTIFY_DONE;
 
+        if (args->regs && user_mode(args->regs))
+                return ret;
+
         switch (val) {
         case DIE_INT3:
                 if (kprobe_handler(args->regs))