[PATCH] kprobes: fix broken fault handling for x86_64

[linux-2.6] / arch / x86_64 / kernel / kprobes.c

diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 218e015c319545a60d6d49f3f97fbe476235e82b..accbff3fec491826071ad572c19d0207413a1bca 100644 (file)
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -37,10 +37,12 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/preempt.h>
+#include <linux/module.h>
 
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
 #include <asm/kdebug.h>
+#include <asm/uaccess.h>
 
 void jprobe_return_end(void);
 static void __kprobes arch_copy_kprobe(struct kprobe *p);
@@ -578,16 +580,62 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 {
        struct kprobe *cur = kprobe_running();
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+       const struct exception_table_entry *fixup;
 
-       if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
-               return 1;
-
-       if (kcb->kprobe_status & KPROBE_HIT_SS) {
-               resume_execution(cur, regs, kcb);
+       switch(kcb->kprobe_status) {
+       case KPROBE_HIT_SS:
+       case KPROBE_REENTER:
+               /*
+                * We are here because the instruction being single
+                * stepped caused a page fault. We reset the current
+                * kprobe and the rip points back to the probe address
+                * and allow the page fault handler to continue as a
+                * normal page fault.
+                */
+               regs->rip = (unsigned long)cur->addr;
                regs->eflags |= kcb->kprobe_old_rflags;
-
-               reset_current_kprobe();
+               if (kcb->kprobe_status == KPROBE_REENTER)
+                       restore_previous_kprobe(kcb);
+               else
+                       reset_current_kprobe();
                preempt_enable_no_resched();
+               break;
+       case KPROBE_HIT_ACTIVE:
+       case KPROBE_HIT_SSDONE:
+               /*
+                * We increment the nmissed count for accounting,
+                * we can also use npre/npostfault count for accouting
+                * these specific fault cases.
+                */
+               kprobes_inc_nmissed_count(cur);
+
+               /*
+                * We come here because instructions in the pre/post
+                * handler caused the page_fault, this could happen
+                * if handler tries to access user space by
+                * copy_from_user(), get_user() etc. Let the
+                * user-specified handler try to fix it first.
+                */
+               if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
+                       return 1;
+
+               /*
+                * In case the user-specified fault handler returned
+                * zero, try to fix up.
+                */
+               fixup = search_exception_tables(regs->rip);
+               if (fixup) {
+                       regs->rip = fixup->fixup;
+                       return 1;
+               }
+
+               /*
+                * fixup() could not handle it,
+                * Let do_page_fault() fix it.
+                */
+               break;
+       default:
+               break;
        }
        return 0;
 }