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-rw-r--r--arch/x86/kernel/ftrace.c88
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 */