1 files changed, 160 insertions, 16 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 59ff9b455069..3762f6b35ab2 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -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>
@@ -30,15 +33,14 @@
 #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 +127,50 @@ static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
                 regs->eip = (unsigned long)&p->ainsn.insn;
 }
 
+struct task_struct  *arch_get_kprobe_task(void *ptr)
+{
+        return ((struct thread_info *) (((unsigned long) ptr) &
+                                        (~(THREAD_SIZE -1))))->task;
+}
+
+void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
+{
+        unsigned long *sara = (unsigned long *)&regs->esp;
+        struct kretprobe_instance *ri;
+        static void *orig_ret_addr;
+
+        /*
+         * Save the return address when the return probe hits
+         * the first time, and use it to populate the (krprobe
+         * instance)->ret_addr for subsequent return probes at
+         * the same addrress since stack address would have
+         * the kretprobe_trampoline by then.
+         */
+        if (((void*) *sara) != kretprobe_trampoline)
+                orig_ret_addr = (void*) *sara;
+
+        if ((ri = get_free_rp_inst(rp)) != NULL) {
+                ri->rp = rp;
+                ri->stack_addr = sara;
+                ri->ret_addr = orig_ret_addr;
+                add_rp_inst(ri);
+                /* Replace the return addr with trampoline addr */
+                *sara = (unsigned long) &kretprobe_trampoline;
+        } else {
+                rp->nmissed++;
+        }
+}
+
+void arch_kprobe_flush_task(struct task_struct *tk)
+{
+        struct kretprobe_instance *ri;
+        while ((ri = get_rp_inst_tsk(tk)) != NULL) {
+                *((unsigned long *)(ri->stack_addr)) =
+                                        (unsigned long) ri->ret_addr;
+                recycle_rp_inst(ri);
+        }
+}
+
 /*
  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
  * remain disabled thorough out this function.
@@ -127,8 +207,18 @@ 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 +253,7 @@ 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 +270,55 @@ 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 task_struct *tsk;
+        struct kretprobe_instance *ri;
+        struct hlist_head *head;
+        struct hlist_node *node;
+        unsigned long *sara = ((unsigned long *) &regs->esp) - 1;
+
+        tsk = arch_get_kprobe_task(sara);
+        head = kretprobe_inst_table_head(tsk);
+
+        hlist_for_each_entry(ri, node, head, hlist) {
+                if (ri->stack_addr == sara && ri->rp) {
+                        if (ri->rp->handler)
+                                ri->rp->handler(ri, regs);
+                }
+        }
+        return 0;
+}
+
+void trampoline_post_handler(struct kprobe *p, struct pt_regs *regs,
+                                                unsigned long flags)
+{
+        struct kretprobe_instance *ri;
+        /* RA already popped */
+        unsigned long *sara = ((unsigned long *)&regs->esp) - 1;
+
+        while ((ri = get_rp_inst(sara))) {
+                regs->eip = (unsigned long)ri->ret_addr;
+                recycle_rp_inst(ri);
+        }
+        regs->eflags &= ~TF_MASK;
+}
+
+/*
  * 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 +398,22 @@ 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);
+        if (current_kprobe->post_handler != trampoline_post_handler)
+                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();
 
         /*