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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt8
-rw-r--r--include/linux/ftrace.h11
-rw-r--r--kernel/trace/ftrace.c2
-rw-r--r--kernel/trace/trace.c18
4 files changed, 38 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f5a27f067db9..f6b7ee64ace8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1435,6 +1435,14 @@
as early as possible in order to facilitate early
boot debugging.
+ ftrace_boot_snapshot
+ [FTRACE] On boot up, a snapshot will be taken of the
+ ftrace ring buffer that can be read at:
+ /sys/kernel/tracing/snapshot.
+ This is useful if you need tracing information from kernel
+ boot up that is likely to be overridden by user space
+ start up functionality.
+
ftrace_dump_on_oops[=orig_cpu]
[FTRACE] will dump the trace buffers on oops.
If no parameter is passed, ftrace will dump
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9999e29187de..37b619185ec9 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -30,6 +30,12 @@
#define ARCH_SUPPORTS_FTRACE_OPS 0
#endif
+#ifdef CONFIG_TRACING
+extern void ftrace_boot_snapshot(void);
+#else
+static inline void ftrace_boot_snapshot(void) { }
+#endif
+
#ifdef CONFIG_FUNCTION_TRACER
struct ftrace_ops;
struct ftrace_regs;
@@ -215,7 +221,10 @@ struct ftrace_ops_hash {
void ftrace_free_init_mem(void);
void ftrace_free_mem(struct module *mod, void *start, void *end);
#else
-static inline void ftrace_free_init_mem(void) { }
+static inline void ftrace_free_init_mem(void)
+{
+ ftrace_boot_snapshot();
+}
static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { }
#endif
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9feb197b2da..4e29bd1cf151 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7096,6 +7096,8 @@ void __init ftrace_free_init_mem(void)
void *start = (void *)(&__init_begin);
void *end = (void *)(&__init_end);
+ ftrace_boot_snapshot();
+
ftrace_free_mem(NULL, start, end);
}
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7c85ce9ffdc3..eaf7d30ca6f1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -185,6 +185,7 @@ static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
static char *default_bootup_tracer;
static bool allocate_snapshot;
+static bool snapshot_at_boot;
static int __init set_cmdline_ftrace(char *str)
{
@@ -230,6 +231,15 @@ static int __init boot_alloc_snapshot(char *str)
__setup("alloc_snapshot", boot_alloc_snapshot);
+static int __init boot_snapshot(char *str)
+{
+ snapshot_at_boot = true;
+ boot_alloc_snapshot(str);
+ return 1;
+}
+__setup("ftrace_boot_snapshot", boot_snapshot);
+
+
static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
static int __init set_trace_boot_options(char *str)
@@ -10149,6 +10159,14 @@ out:
return ret;
}
+void __init ftrace_boot_snapshot(void)
+{
+ if (snapshot_at_boot) {
+ tracing_snapshot();
+ internal_trace_puts("** Boot snapshot taken **\n");
+ }
+}
+
void __init early_trace_init(void)
{
if (tracepoint_printk) {