[PATCH] kprobes: Temporary disarming of reentrant probe for sparc64

This patch includes sparc64 architecture specific changes to support temporary
disarming on reentrancy of probes.

Signed-of-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 49 insertions, 13 deletions

diff --git a/arch/sparc64/kernel/kprobes.c b/arch/sparc64/kernel/kprobes.c
index d67195ba3fa2..bdac631cf011 100644
--- a/arch/sparc64/kernel/kprobes.c
+++ b/arch/sparc64/kernel/kprobes.c
@@ -65,19 +65,40 @@ void arch_remove_kprobe(struct kprobe *p)
 {
 }
 
-/* kprobe_status settings */
-#define KPROBE_HIT_ACTIVE       0x00000001
-#define KPROBE_HIT_SS           0x00000002
-
 static struct kprobe *current_kprobe;
 static unsigned long current_kprobe_orig_tnpc;
 static unsigned long current_kprobe_orig_tstate_pil;
 static unsigned int kprobe_status;
+static struct kprobe *kprobe_prev;
+static unsigned long kprobe_orig_tnpc_prev;
+static unsigned long kprobe_orig_tstate_pil_prev;
+static unsigned int kprobe_status_prev;
 
-static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+static inline void save_previous_kprobe(void)
+{
+        kprobe_status_prev = kprobe_status;
+        kprobe_orig_tnpc_prev = current_kprobe_orig_tnpc;
+        kprobe_orig_tstate_pil_prev = current_kprobe_orig_tstate_pil;
+        kprobe_prev = current_kprobe;
+}
+
+static inline void restore_previous_kprobe(void)
+{
+        kprobe_status = kprobe_status_prev;
+        current_kprobe_orig_tnpc = kprobe_orig_tnpc_prev;
+        current_kprobe_orig_tstate_pil = kprobe_orig_tstate_pil_prev;
+        current_kprobe = kprobe_prev;
+}
+
+static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
 {
         current_kprobe_orig_tnpc = regs->tnpc;
         current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
+        current_kprobe = p;
+}
+
+static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
         regs->tstate |= TSTATE_PIL;
 
         /*single step inline, if it a breakpoint instruction*/
@@ -110,12 +131,18 @@ static int kprobe_handler(struct pt_regs *regs)
                                 unlock_kprobes();
                                 goto no_kprobe;
                         }
-                        arch_disarm_kprobe(p);
-                        regs->tpc = (unsigned long) p->addr;
-                        regs->tnpc = current_kprobe_orig_tnpc;
-                        regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
-                                        current_kprobe_orig_tstate_pil);
-                        ret = 1;
+                        /* We have reentered the kprobe_handler(), since
+                         * another probe was hit while within the handler.
+                         * We here save the original kprobes variables and
+                         * just single step on the instruction of the new probe
+                         * without calling any user handlers.
+                         */
+                        save_previous_kprobe();
+                        set_current_kprobe(p, regs);
+                        p->nmissed++;
+                        kprobe_status = KPROBE_REENTER;
+                        prepare_singlestep(p, regs);
+                        return 1;
                 } else {
                         p = current_kprobe;
                         if (p->break_handler && p->break_handler(p, regs))
@@ -143,8 +170,8 @@ static int kprobe_handler(struct pt_regs *regs)
                 goto no_kprobe;
         }
 
+        set_current_kprobe(p, regs);
         kprobe_status = KPROBE_HIT_ACTIVE;
-        current_kprobe = p;
         if (p->pre_handler && p->pre_handler(p, regs))
                 return 1;
 
@@ -250,12 +277,20 @@ static inline int post_kprobe_handler(struct pt_regs *regs)
         if (!kprobe_running())
                 return 0;
 
-        if (current_kprobe->post_handler)
+        if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
+                kprobe_status = KPROBE_HIT_SSDONE;
                 current_kprobe->post_handler(current_kprobe, regs, 0);
+        }
 
         resume_execution(current_kprobe, regs);
 
+        /*Restore back the original saved kprobes variables and continue. */
+        if (kprobe_status == KPROBE_REENTER) {
+                restore_previous_kprobe();
+                goto out;
+        }
         unlock_kprobes();
+out:
         preempt_enable_no_resched();
 
         return 1;
@@ -397,3 +432,4 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
         }
         return 0;
 }
+