[PATCH] Kprobes/ia64: temporary disarming of reentrant probe
authorAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Thu, 23 Jun 2005 07:09:40 +0000 (00:09 -0700)
committerLinus Torvalds <torvalds@ppc970.osdl.org>
Thu, 23 Jun 2005 16:45:25 +0000 (09:45 -0700)
This patch includes IA64 architecture specific changes(ported form i386) to
support temporary disarming on reentrancy of probes.

In case of reentrancy we single step without calling user handler.

Signed-of-by: Anil S Keshavamurth <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
arch/ia64/kernel/kprobes.c

index 41e80b42d3f3cd80b74bae3467d06f7ebad27589..5978823d5c63ce3fbc891c2108ddd6c98579e739 100644 (file)
@@ -41,8 +41,8 @@ extern void jprobe_inst_return(void);
 #define KPROBE_HIT_ACTIVE      0x00000001
 #define KPROBE_HIT_SS          0x00000002
 
-static struct kprobe *current_kprobe;
-static unsigned long kprobe_status;
+static struct kprobe *current_kprobe, *kprobe_prev;
+static unsigned long kprobe_status, kprobe_status_prev;
 static struct pt_regs jprobe_saved_regs;
 
 enum instruction_type {A, I, M, F, B, L, X, u};
@@ -273,6 +273,23 @@ static int valid_kprobe_addr(int template, int slot, unsigned long addr)
        return 0;
 }
 
+static inline void save_previous_kprobe(void)
+{
+       kprobe_prev = current_kprobe;
+       kprobe_status_prev = kprobe_status;
+}
+
+static inline void restore_previous_kprobe(void)
+{
+       current_kprobe = kprobe_prev;
+       kprobe_status = kprobe_status_prev;
+}
+
+static inline void set_current_kprobe(struct kprobe *p)
+{
+       current_kprobe = p;
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
        unsigned long addr = (unsigned long) p->addr;
@@ -436,8 +453,18 @@ static int pre_kprobes_handler(struct die_args *args)
                                unlock_kprobes();
                                goto no_kprobe;
                        }
-                       arch_disarm_kprobe(p);
-                       ret = 1;
+                       /* We have reentered the pre_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);
+                       p->nmissed++;
+                       prepare_ss(p, regs);
+                       kprobe_status = KPROBE_REENTER;
+                       return 1;
                } else if (args->err == __IA64_BREAK_JPROBE) {
                        /*
                         * jprobe instrumented function just completed
@@ -460,7 +487,7 @@ static int pre_kprobes_handler(struct die_args *args)
        }
 
        kprobe_status = KPROBE_HIT_ACTIVE;
-       current_kprobe = p;
+       set_current_kprobe(p);
 
        if (p->pre_handler && p->pre_handler(p, regs))
                /*
@@ -485,12 +512,22 @@ static int post_kprobes_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;
 }