[PATCH] kprobes: fix namespace problem and sparc64 build
[linux-2.6.git] / arch / i386 / kernel / kprobes.c
index 59ff9b4..a6d8c45 100644 (file)
@@ -23,6 +23,9 @@
  *             Rusty Russell).
  * 2004-July   Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
  *             interface to access function arguments.
+ * 2005-May    Hien Nguyen <hien@us.ibm.com>, Jim Keniston
+ *             <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
+ *             <prasanna@in.ibm.com> added function-return probes.
  */
 
 #include <linux/config.h>
 #include <linux/ptrace.h>
 #include <linux/spinlock.h>
 #include <linux/preempt.h>
+#include <asm/cacheflush.h>
 #include <asm/kdebug.h>
 #include <asm/desc.h>
 
-/* kprobe_status settings */
-#define KPROBE_HIT_ACTIVE      0x00000001
-#define KPROBE_HIT_SS          0x00000002
-
 static struct kprobe *current_kprobe;
 static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
+static struct kprobe *kprobe_prev;
+static unsigned long kprobe_status_prev, kprobe_old_eflags_prev, kprobe_saved_eflags_prev;
 static struct pt_regs jprobe_saved_regs;
 static long *jprobe_saved_esp;
 /* copy of the kernel stack at the probe fire time */
@@ -68,16 +70,50 @@ int arch_prepare_kprobe(struct kprobe *p)
 void arch_copy_kprobe(struct kprobe *p)
 {
        memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+       p->opcode = *p->addr;
 }
 
-void arch_remove_kprobe(struct kprobe *p)
+void arch_arm_kprobe(struct kprobe *p)
 {
+       *p->addr = BREAKPOINT_INSTRUCTION;
+       flush_icache_range((unsigned long) p->addr,
+                          (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 }
 
-static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+void arch_disarm_kprobe(struct kprobe *p)
 {
        *p->addr = p->opcode;
-       regs->eip = (unsigned long)p->addr;
+       flush_icache_range((unsigned long) p->addr,
+                          (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+}
+
+static inline void save_previous_kprobe(void)
+{
+       kprobe_prev = current_kprobe;
+       kprobe_status_prev = kprobe_status;
+       kprobe_old_eflags_prev = kprobe_old_eflags;
+       kprobe_saved_eflags_prev = kprobe_saved_eflags;
+}
+
+static inline void restore_previous_kprobe(void)
+{
+       current_kprobe = kprobe_prev;
+       kprobe_status = kprobe_status_prev;
+       kprobe_old_eflags = kprobe_old_eflags_prev;
+       kprobe_saved_eflags = kprobe_saved_eflags_prev;
+}
+
+static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
+{
+       current_kprobe = p;
+       kprobe_saved_eflags = kprobe_old_eflags
+               = (regs->eflags & (TF_MASK | IF_MASK));
+       if (is_IF_modifier(p->opcode))
+               kprobe_saved_eflags &= ~IF_MASK;
 }
 
 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -91,6 +127,25 @@ static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
                regs->eip = (unsigned long)&p->ainsn.insn;
 }
 
+void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
+{
+       unsigned long *sara = (unsigned long *)&regs->esp;
+        struct kretprobe_instance *ri;
+
+        if ((ri = get_free_rp_inst(rp)) != NULL) {
+                ri->rp = rp;
+                ri->task = current;
+               ri->ret_addr = (kprobe_opcode_t *) *sara;
+
+               /* Replace the return addr with trampoline addr */
+               *sara = (unsigned long) &kretprobe_trampoline;
+
+                add_rp_inst(ri);
+        } else {
+                rp->nmissed++;
+        }
+}
+
 /*
  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
  * remain disabled thorough out this function.
@@ -127,8 +182,18 @@ static int kprobe_handler(struct pt_regs *regs)
                                unlock_kprobes();
                                goto no_kprobe;
                        }
-                       disarm_kprobe(p, regs);
-                       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++;
+                       prepare_singlestep(p, regs);
+                       kprobe_status = KPROBE_REENTER;
+                       return 1;
                } else {
                        p = current_kprobe;
                        if (p->break_handler && p->break_handler(p, regs)) {
@@ -163,11 +228,7 @@ static int kprobe_handler(struct pt_regs *regs)
        }
 
        kprobe_status = KPROBE_HIT_ACTIVE;
-       current_kprobe = p;
-       kprobe_saved_eflags = kprobe_old_eflags
-           = (regs->eflags & (TF_MASK | IF_MASK));
-       if (is_IF_modifier(p->opcode))
-               kprobe_saved_eflags &= ~IF_MASK;
+       set_current_kprobe(p, regs);
 
        if (p->pre_handler && p->pre_handler(p, regs))
                /* handler has already set things up, so skip ss setup */
@@ -184,6 +245,78 @@ no_kprobe:
 }
 
 /*
+ * For function-return probes, init_kprobes() establishes a probepoint
+ * here. When a retprobed function returns, this probe is hit and
+ * trampoline_probe_handler() runs, calling the kretprobe's handler.
+ */
+ void kretprobe_trampoline_holder(void)
+ {
+       asm volatile (  ".global kretprobe_trampoline\n"
+                       "kretprobe_trampoline: \n"
+                       "nop\n");
+ }
+
+/*
+ * Called when we hit the probe point at kretprobe_trampoline
+ */
+int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+        struct kretprobe_instance *ri = NULL;
+        struct hlist_head *head;
+        struct hlist_node *node, *tmp;
+       unsigned long orig_ret_address = 0;
+       unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
+
+        head = kretprobe_inst_table_head(current);
+
+       /*
+        * It is possible to have multiple instances associated with a given
+        * task either because an multiple functions in the call path
+        * have a return probe installed on them, and/or more then one return
+        * return probe was registered for a target function.
+        *
+        * We can handle this because:
+        *     - instances are always inserted at the head of the list
+        *     - when multiple return probes are registered for the same
+         *       function, the first instance's ret_addr will point to the
+        *       real return address, and all the rest will point to
+        *       kretprobe_trampoline
+        */
+       hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+                if (ri->task != current)
+                       /* another task is sharing our hash bucket */
+                        continue;
+
+               if (ri->rp && ri->rp->handler)
+                       ri->rp->handler(ri, regs);
+
+               orig_ret_address = (unsigned long)ri->ret_addr;
+               recycle_rp_inst(ri);
+
+               if (orig_ret_address != trampoline_address)
+                       /*
+                        * This is the real return address. Any other
+                        * instances associated with this task are for
+                        * other calls deeper on the call stack
+                        */
+                       break;
+       }
+
+       BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+       regs->eip = orig_ret_address;
+
+       unlock_kprobes();
+       preempt_enable_no_resched();
+
+        /*
+         * By returning a non-zero value, we are telling
+         * kprobe_handler() that we have handled unlocking
+         * and re-enabling preemption.
+         */
+        return 1;
+}
+
+/*
  * Called after single-stepping.  p->addr is the address of the
  * instruction whose first byte has been replaced by the "int 3"
  * instruction.  To avoid the SMP problems that can occur when we
@@ -263,13 +396,21 @@ 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);
        regs->eflags |= kprobe_saved_eflags;
 
+       /*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();
 
        /*
@@ -390,3 +531,13 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
        }
        return 0;
 }
+
+static struct kprobe trampoline_p = {
+       .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+       .pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+       return register_kprobe(&trampoline_p);
+}