Merge tag 'for-linus-20140225' of git://git.infradead.org/linux-mtd

[~andy/linux] / arch / x86 / kernel / ftrace.c

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index d4bdd253fea71358ca080ba567a44935a9830396..e6253195a301ade244143d4d13a73c947602a0cb 100644 (file)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -77,8 +77,7 @@ within(unsigned long addr, unsigned long start, unsigned long end)
        return addr >= start && addr < end;
 }
 
-static int
-do_ftrace_mod_code(unsigned long ip, const void *new_code)
+static unsigned long text_ip_addr(unsigned long ip)
 {
        /*
         * On x86_64, kernel text mappings are mapped read-only with
@@ -91,7 +90,7 @@ do_ftrace_mod_code(unsigned long ip, const void *new_code)
        if (within(ip, (unsigned long)_text, (unsigned long)_etext))
                ip = (unsigned long)__va(__pa_symbol(ip));
 
-       return probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE);
+       return ip;
 }
 
 static const unsigned char *ftrace_nop_replace(void)
@@ -123,8 +122,10 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
        if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
                return -EINVAL;
 
+       ip = text_ip_addr(ip);
+
        /* replace the text with the new text */
-       if (do_ftrace_mod_code(ip, new_code))
+       if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
                return -EPERM;
 
        sync_core();
@@ -221,37 +222,51 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
        return -EINVAL;
 }
 
-int ftrace_update_ftrace_func(ftrace_func_t func)
+static unsigned long ftrace_update_func;
+
+static int update_ftrace_func(unsigned long ip, void *new)
 {
-       unsigned long ip = (unsigned long)(&ftrace_call);
-       unsigned char old[MCOUNT_INSN_SIZE], *new;
+       unsigned char old[MCOUNT_INSN_SIZE];
        int ret;
 
-       memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
-       new = ftrace_call_replace(ip, (unsigned long)func);
+       memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
+
+       ftrace_update_func = ip;
+       /* Make sure the breakpoints see the ftrace_update_func update */
+       smp_wmb();
 
        /* 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;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+       unsigned long ip = (unsigned long)(&ftrace_call);
+       unsigned char *new;
+       int ret;
+
+       new = ftrace_call_replace(ip, (unsigned long)func);
+       ret = update_ftrace_func(ip, new);
+
        /* Also update the regs callback function */
        if (!ret) {
                ip = (unsigned long)(&ftrace_regs_call);
-               memcpy(old, &ftrace_regs_call, MCOUNT_INSN_SIZE);
                new = ftrace_call_replace(ip, (unsigned long)func);
-               ret = ftrace_modify_code(ip, old, new);
+               ret = update_ftrace_func(ip, new);
        }
 
-       atomic_dec(&modifying_ftrace_code);
-
        return ret;
 }
 
 static int is_ftrace_caller(unsigned long ip)
 {
-       if (ip == (unsigned long)(&ftrace_call) ||
-               ip == (unsigned long)(&ftrace_regs_call))
+       if (ip == ftrace_update_func)
                return 1;
 
        return 0;
@@ -677,45 +692,41 @@ int __init ftrace_dyn_arch_init(void *data)
 #ifdef CONFIG_DYNAMIC_FTRACE
 extern void ftrace_graph_call(void);
 
-static int ftrace_mod_jmp(unsigned long ip,
-                         int old_offset, int new_offset)
+static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
 {
-       unsigned char code[MCOUNT_INSN_SIZE];
+       static union ftrace_code_union calc;
 
-       if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
-               return -EFAULT;
+       /* Jmp not a call (ignore the .e8) */
+       calc.e8         = 0xe9;
+       calc.offset     = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
 
-       if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
-               return -EINVAL;
+       /*
+        * ftrace external locks synchronize the access to the static variable.
+        */
+       return calc.code;
+}
 
-       *(int *)(&code[1]) = new_offset;
+static int ftrace_mod_jmp(unsigned long ip, void *func)
+{
+       unsigned char *new;
 
-       if (do_ftrace_mod_code(ip, &code))
-               return -EPERM;
+       new = ftrace_jmp_replace(ip, (unsigned long)func);
 
-       return 0;
+       return update_ftrace_func(ip, new);
 }
 
 int ftrace_enable_ftrace_graph_caller(void)
 {
        unsigned long ip = (unsigned long)(&ftrace_graph_call);
-       int old_offset, new_offset;
 
-       old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
-       new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
-
-       return ftrace_mod_jmp(ip, old_offset, new_offset);
+       return ftrace_mod_jmp(ip, &ftrace_graph_caller);
 }
 
 int ftrace_disable_ftrace_graph_caller(void)
 {
        unsigned long ip = (unsigned long)(&ftrace_graph_call);
-       int old_offset, new_offset;
-
-       old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
-       new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
 
-       return ftrace_mod_jmp(ip, old_offset, new_offset);
+       return ftrace_mod_jmp(ip, &ftrace_stub);
 }
 
 #endif /* !CONFIG_DYNAMIC_FTRACE */