1 files changed, 44 insertions, 48 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index bebc3007a793..ca5d5a081e75 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -43,12 +43,6 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
 
-int is_current_kprobe_addr(unsigned long addr)
-{
-        struct kprobe *p = kprobe_running();
-        return (p && (unsigned long)p->addr == addr) ? 1 : 0;
-}
-
 bool arch_within_kprobe_blacklist(unsigned long addr)
 {
         return  (addr >= (unsigned long)__kprobes_text_start &&
@@ -59,7 +53,7 @@ bool arch_within_kprobe_blacklist(unsigned long addr)
 
 kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 {
-        kprobe_opcode_t *addr;
+        kprobe_opcode_t *addr = NULL;
 
 #ifdef PPC64_ELF_ABI_v2
         /* PPC64 ABIv2 needs local entry point */
@@ -91,36 +85,29 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
          * Also handle <module:symbol> format.
          */
         char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
-        const char *modsym;
         bool dot_appended = false;
-        if ((modsym = strchr(name, ':')) != NULL) {
-                modsym++;
-                if (*modsym != '\0' && *modsym != '.') {
-                        /* Convert to <module:.symbol> */
-                        strncpy(dot_name, name, modsym - name);
-                        dot_name[modsym - name] = '.';
-                        dot_name[modsym - name + 1] = '\0';
-                        strncat(dot_name, modsym,
-                                sizeof(dot_name) - (modsym - name) - 2);
-                        dot_appended = true;
-                } else {
-                        dot_name[0] = '\0';
-                        strncat(dot_name, name, sizeof(dot_name) - 1);
-                }
-        } else if (name[0] != '.') {
-                dot_name[0] = '.';
-                dot_name[1] = '\0';
-                strncat(dot_name, name, KSYM_NAME_LEN - 2);
+        const char *c;
+        ssize_t ret = 0;
+        int len = 0;
+
+        if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
+                c++;
+                len = c - name;
+                memcpy(dot_name, name, len);
+        } else
+                c = name;
+
+        if (*c != '\0' && *c != '.') {
+                dot_name[len++] = '.';
                 dot_appended = true;
-        } else {
-                dot_name[0] = '\0';
-                strncat(dot_name, name, KSYM_NAME_LEN - 1);
         }
-        addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
-        if (!addr && dot_appended) {
-                /* Let's try the original non-dot symbol lookup */
+        ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
+        if (ret > 0)
+                addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
+
+        /* Fallback to the original non-dot symbol lookup */
+        if (!addr && dot_appended)
                 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
-        }
 #else
         addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
 #endif
@@ -239,7 +226,7 @@ void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 
-int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
+static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
 {
         int ret;
         unsigned int insn = *p->ainsn.insn;
@@ -261,9 +248,20 @@ int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
                  */
                 printk("Can't step on instruction %x\n", insn);
                 BUG();
-        } else if (ret == 0)
-                /* This instruction can't be boosted */
-                p->ainsn.boostable = -1;
+        } else {
+                /*
+                 * If we haven't previously emulated this instruction, then it
+                 * can't be boosted. Note it down so we don't try to do so again.
+                 *
+                 * If, however, we had emulated this instruction in the past,
+                 * then this is just an error with the current run (for
+                 * instance, exceptions due to a load/store). We return 0 so
+                 * that this is now single-stepped, but continue to try
+                 * emulating it in subsequent probe hits.
+                 */
+                if (unlikely(p->ainsn.boostable != 1))
+                        p->ainsn.boostable = -1;
+        }
 
         return ret;
 }
@@ -639,24 +637,22 @@ NOKPROBE_SYMBOL(setjmp_pre_handler);
 
 void __used jprobe_return(void)
 {
-        asm volatile("trap" ::: "memory");
+        asm volatile("jprobe_return_trap:\n"
+                     "trap\n"
+                     ::: "memory");
 }
 NOKPROBE_SYMBOL(jprobe_return);
 
-static void __used jprobe_return_end(void)
-{
-}
-NOKPROBE_SYMBOL(jprobe_return_end);
-
 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 {
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 
-        /*
-         * FIXME - we should ideally be validating that we got here 'cos
-         * of the "trap" in jprobe_return() above, before restoring the
-         * saved regs...
-         */
+        if (regs->nip != ppc_kallsyms_lookup_name("jprobe_return_trap")) {
+                pr_debug("longjmp_break_handler NIP (0x%lx) does not match jprobe_return_trap (0x%lx)\n",
+                                regs->nip, ppc_kallsyms_lookup_name("jprobe_return_trap"));
+                return 0;
+        }
+
         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
         /* It's OK to start function graph tracing again */
         unpause_graph_tracing();