1 files changed, 72 insertions, 16 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 2407a6d81cb7..c3a7cb4bf6e6 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -100,7 +100,7 @@ static const unsigned char *ftrace_nop_replace(void)
 }
 
 static int
-ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
+ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
                    unsigned const char *new_code)
 {
         unsigned char replaced[MCOUNT_INSN_SIZE];
@@ -141,7 +141,20 @@ int ftrace_make_nop(struct module *mod,
         old = ftrace_call_replace(ip, addr);
         new = ftrace_nop_replace();
 
-        return ftrace_modify_code(rec->ip, old, new);
+        /*
+         * On boot up, and when modules are loaded, the MCOUNT_ADDR
+         * is converted to a nop, and will never become MCOUNT_ADDR
+         * again. This code is either running before SMP (on boot up)
+         * or before the code will ever be executed (module load).
+         * We do not want to use the breakpoint version in this case,
+         * just modify the code directly.
+         */
+        if (addr == MCOUNT_ADDR)
+                return ftrace_modify_code_direct(rec->ip, old, new);
+
+        /* Normal cases use add_brk_on_nop */
+        WARN_ONCE(1, "invalid use of ftrace_make_nop");
+        return -EINVAL;
 }
 
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
@@ -152,20 +165,8 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
         old = ftrace_nop_replace();
         new = ftrace_call_replace(ip, addr);
 
-        return ftrace_modify_code(rec->ip, old, new);
-}
-
-int ftrace_update_ftrace_func(ftrace_func_t func)
-{
-        unsigned long ip = (unsigned long)(&ftrace_call);
-        unsigned char old[MCOUNT_INSN_SIZE], *new;
-        int ret;
-
-        memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
-        new = ftrace_call_replace(ip, (unsigned long)func);
-        ret = ftrace_modify_code(ip, old, new);
-
-        return ret;
+        /* Should only be called when module is loaded */
+        return ftrace_modify_code_direct(rec->ip, old, new);
 }
 
 /*
@@ -201,6 +202,29 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
  */
 atomic_t modifying_ftrace_code __read_mostly;
 
+static int
+ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
+                   unsigned const char *new_code);
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+        unsigned long ip = (unsigned long)(&ftrace_call);
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
+        int ret;
+
+        memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
+        new = ftrace_call_replace(ip, (unsigned long)func);
+
+        /* See comment above by declaration of modifying_ftrace_code */
+        atomic_inc(&modifying_ftrace_code);
+
+        ret = ftrace_modify_code(ip, old, new);
+
+        atomic_dec(&modifying_ftrace_code);
+
+        return ret;
+}
+
 /*
  * A breakpoint was added to the code address we are about to
  * modify, and this is the handle that will just skip over it.
@@ -520,6 +544,38 @@ void ftrace_replace_code(int enable)
         }
 }
 
+static int
+ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
+                   unsigned const char *new_code)
+{
+        int ret;
+
+        ret = add_break(ip, old_code);
+        if (ret)
+                goto out;
+
+        run_sync();
+
+        ret = add_update_code(ip, new_code);
+        if (ret)
+                goto fail_update;
+
+        run_sync();
+
+        ret = ftrace_write(ip, new_code, 1);
+        if (ret) {
+                ret = -EPERM;
+                goto out;
+        }
+        run_sync();
+ out:
+        return ret;
+
+ fail_update:
+        probe_kernel_write((void *)ip, &old_code[0], 1);
+        goto out;
+}
+
 void arch_ftrace_update_code(int command)
 {
         /* See comment above by declaration of modifying_ftrace_code */