Merge branch 'perf/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic...

[safe/jmp/linux-2.6] / arch / x86 / kernel / ftrace.c

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 944e982..cd37469 100644 (file)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -9,6 +9,8 @@
  * the dangers of modifying code on the run.
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
 #include <linux/uaccess.h>
@@ -28,14 +30,32 @@
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
+/*
+ * modifying_code is set to notify NMIs that they need to use
+ * memory barriers when entering or exiting. But we don't want
+ * to burden NMIs with unnecessary memory barriers when code
+ * modification is not being done (which is most of the time).
+ *
+ * A mutex is already held when ftrace_arch_code_modify_prepare
+ * and post_process are called. No locks need to be taken here.
+ *
+ * Stop machine will make sure currently running NMIs are done
+ * and new NMIs will see the updated variable before we need
+ * to worry about NMIs doing memory barriers.
+ */
+static int modifying_code __read_mostly;
+static DEFINE_PER_CPU(int, save_modifying_code);
+
 int ftrace_arch_code_modify_prepare(void)
 {
        set_kernel_text_rw();
+       modifying_code = 1;
        return 0;
 }
 
 int ftrace_arch_code_modify_post_process(void)
 {
+       modifying_code = 0;
        set_kernel_text_ro();
        return 0;
 }
@@ -147,6 +167,11 @@ static void ftrace_mod_code(void)
 
 void ftrace_nmi_enter(void)
 {
+       __get_cpu_var(save_modifying_code) = modifying_code;
+
+       if (!__get_cpu_var(save_modifying_code))
+               return;
+
        if (atomic_inc_return(&nmi_running) & MOD_CODE_WRITE_FLAG) {
                smp_rmb();
                ftrace_mod_code();
@@ -158,6 +183,9 @@ void ftrace_nmi_enter(void)
 
 void ftrace_nmi_exit(void)
 {
+       if (!__get_cpu_var(save_modifying_code))
+               return;
+
        /* Finish all executions before clearing nmi_running */
        smp_mb();
        atomic_dec(&nmi_running);
@@ -353,15 +381,15 @@ int __init ftrace_dyn_arch_init(void *data)
 
        switch (faulted) {
        case 0:
-               pr_info("ftrace: converting mcount calls to 0f 1f 44 00 00\n");
+               pr_info("converting mcount calls to 0f 1f 44 00 00\n");
                memcpy(ftrace_nop, ftrace_test_p6nop, MCOUNT_INSN_SIZE);
                break;
        case 1:
-               pr_info("ftrace: converting mcount calls to 66 66 66 66 90\n");
+               pr_info("converting mcount calls to 66 66 66 66 90\n");
                memcpy(ftrace_nop, ftrace_test_nop5, MCOUNT_INSN_SIZE);
                break;
        case 2:
-               pr_info("ftrace: converting mcount calls to jmp . + 5\n");
+               pr_info("converting mcount calls to jmp . + 5\n");
                memcpy(ftrace_nop, ftrace_test_jmp, MCOUNT_INSN_SIZE);
                break;
        }
@@ -482,85 +510,3 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
        }
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-
-#ifdef CONFIG_FTRACE_SYSCALLS
-
-extern unsigned long __start_syscalls_metadata[];
-extern unsigned long __stop_syscalls_metadata[];
-extern unsigned long *sys_call_table;
-
-static struct syscall_metadata **syscalls_metadata;
-
-static struct syscall_metadata *find_syscall_meta(unsigned long *syscall)
-{
-       struct syscall_metadata *start;
-       struct syscall_metadata *stop;
-       char str[KSYM_SYMBOL_LEN];
-
-
-       start = (struct syscall_metadata *)__start_syscalls_metadata;
-       stop = (struct syscall_metadata *)__stop_syscalls_metadata;
-       kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
-
-       for ( ; start < stop; start++) {
-               if (start->name && !strcmp(start->name, str))
-                       return start;
-       }
-       return NULL;
-}
-
-struct syscall_metadata *syscall_nr_to_meta(int nr)
-{
-       if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
-               return NULL;
-
-       return syscalls_metadata[nr];
-}
-
-int syscall_name_to_nr(char *name)
-{
-       int i;
-
-       if (!syscalls_metadata)
-               return -1;
-
-       for (i = 0; i < NR_syscalls; i++) {
-               if (syscalls_metadata[i]) {
-                       if (!strcmp(syscalls_metadata[i]->name, name))
-                               return i;
-               }
-       }
-       return -1;
-}
-
-void set_syscall_enter_id(int num, int id)
-{
-       syscalls_metadata[num]->enter_id = id;
-}
-
-void set_syscall_exit_id(int num, int id)
-{
-       syscalls_metadata[num]->exit_id = id;
-}
-
-static int __init arch_init_ftrace_syscalls(void)
-{
-       int i;
-       struct syscall_metadata *meta;
-       unsigned long **psys_syscall_table = &sys_call_table;
-
-       syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
-                                       NR_syscalls, GFP_KERNEL);
-       if (!syscalls_metadata) {
-               WARN_ON(1);
-               return -ENOMEM;
-       }
-
-       for (i = 0; i < NR_syscalls; i++) {
-               meta = find_syscall_meta(psys_syscall_table[i]);
-               syscalls_metadata[i] = meta;
-       }
-       return 0;
-}
-arch_initcall(arch_init_ftrace_syscalls);
-#endif