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Subject[PATCH 3/5] ftrace: add ftrace_bprintk()
From: Lai Jiangshan <laijs@cn.fujitsu.com>

Impact: Add a generic printk() for ftrace, like ftrace_printk()

ftrace_bprintk() use the infrastructure to record events on ring_buffer.

[fweisbec@gmail.com: ported to latest -tip and made it work if !CONFIG_MODULES]

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
include/asm-generic/vmlinux.lds.h | 3 +
include/linux/ftrace.h | 21 ++++++
include/linux/module.h | 5 ++
kernel/module.c | 6 ++
kernel/trace/trace.c | 15 ++++
kernel/trace/trace_bprintk.c | 132 ++++++++++++++++++++++++++++++++++++-
6 files changed, 181 insertions(+), 1 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 9d97491..13f20f4 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -100,6 +100,9 @@
*(__vermagic) /* Kernel version magic */ \
*(__markers_strings) /* Markers: strings */ \
*(__tracepoints_strings)/* Tracepoints: strings */ \
+ VMLINUX_SYMBOL(__start___trace_bprintk_fmt) = .; \
+ *(__trace_printk_fmt) /* Trace_printk fmt' pointer */ \
+ VMLINUX_SYMBOL(__stop___trace_bprintk_fmt) = .; \
} \
\
.rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 8ac2fac..f82b986 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -224,6 +224,27 @@ extern int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr);

#ifdef CONFIG_TRACE_BPRINTK
extern int trace_vbprintk(unsigned long ip, const char *fmt, va_list args);
+extern int __ftrace_bprintk(unsigned long ip, const char *fmt, ...)
+ __attribute__ ((format (printf, 2, 3)));
+
+static inline void ____ftrace_bprintk_check_format(const char *fmt, ...)
+ __attribute__ ((format (printf, 1, 2)));
+static inline void ____ftrace_bprintk_check_format(const char *fmt, ...) {}
+#define __ftrace_bprintk_check_format(fmt, args...) \
+do { \
+ if (0) \
+ ____ftrace_bprintk_check_format(fmt, ##args); \
+} while (0)
+
+#define ftrace_bprintk(fmt, args...) \
+do { \
+ static char *__attribute__((section("__trace_bprintk_fmt"))) \
+ ftrace_bprintk_fmt = fmt; \
+ __ftrace_bprintk_check_format(fmt, ##args); \
+ __ftrace_bprintk(_THIS_IP_, ftrace_bprintk_fmt, ##args); \
+} while (0)
+#else
+#define ftrace_bprintk ftrace_printk
#endif

/* May be defined in arch */
diff --git a/include/linux/module.h b/include/linux/module.h
index 07b1cb4..c4f2845 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -347,6 +347,11 @@ struct module
unsigned int num_tracepoints;
#endif

+#ifdef CONFIG_TRACE_BPRINTK
+ const char **trace_bprintk_fmt_start;
+ unsigned int num_trace_bprintk_fmt;
+#endif
+
#ifdef CONFIG_MODULE_UNLOAD
/* What modules depend on me? */
struct list_head modules_which_use_me;
diff --git a/kernel/module.c b/kernel/module.c
index 90a6d63..fa96909 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2192,6 +2192,12 @@ static noinline struct module *load_module(void __user *umod,
&mod->num_tracepoints);
#endif

+#ifdef CONFIG_TRACE_BPRINTK
+ mod->trace_bprintk_fmt_start = section_objs(hdr, sechdrs, secstrings,
+ "__trace_bprintk_fmt", sizeof(char *),
+ &mod->num_trace_bprintk_fmt);
+#endif
+
#ifdef CONFIG_MODVERSIONS
if ((mod->num_syms && !mod->crcs)
|| (mod->num_gpl_syms && !mod->gpl_crcs)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3a3ae19..0e30dce 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3627,6 +3627,21 @@ out:
}
EXPORT_SYMBOL_GPL(trace_vbprintk);

+int __ftrace_bprintk(unsigned long ip, const char *fmt, ...)
+{
+ int ret;
+ va_list ap;
+
+ if (!fmt)
+ return 0;
+
+ va_start(ap, fmt);
+ ret = trace_vbprintk(ip, fmt, ap);
+ va_end(ap);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__ftrace_bprintk);
+
static int trace_panic_handler(struct notifier_block *this,
unsigned long event, void *unused)
{
diff --git a/kernel/trace/trace_bprintk.c b/kernel/trace/trace_bprintk.c
index 1f8e532..28e6286 100644
--- a/kernel/trace/trace_bprintk.c
+++ b/kernel/trace/trace_bprintk.c
@@ -19,9 +19,23 @@

#include "trace.h"

+#ifdef CONFIG_MODULES
+
/* binary printk basic */
static DEFINE_MUTEX(btrace_mutex);
static int btrace_metadata_count;
+/*
+ * modules ftrace_bprintk()'s formats are autosaved in struct trace_bprintk_fmt
+ * which are queued on trace_bprintk_fmt_list.
+ */
+static LIST_HEAD(trace_bprintk_fmt_list);
+
+struct trace_bprintk_fmt {
+ struct list_head list;
+ int count;
+ char fmt[0];
+};
+

static inline void lock_btrace(void)
{
@@ -33,6 +47,93 @@ static inline void unlock_btrace(void)
mutex_unlock(&btrace_mutex);
}

+/*
+ * If trace_bprintk() is not active, we release the trace_bprintk's
+ * formats that no modules has reference to.
+ */
+static inline void shrink_trace_bprintk_fmt(void)
+{
+ struct trace_bprintk_fmt *pos, *next;
+ list_for_each_entry_safe(pos, next, &trace_bprintk_fmt_list, list) {
+ if (!pos->count) {
+ list_del(&pos->list);
+ kfree(pos);
+ }
+ }
+}
+
+static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
+{
+ struct trace_bprintk_fmt *pos;
+ list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
+ if (!strcmp(pos->fmt, fmt))
+ return pos;
+ }
+ return NULL;
+}
+
+static
+void hold_module_trace_bprintk_format(const char **start, const char **end)
+{
+ const char **iter;
+ lock_btrace();
+ for (iter = start; iter < end; iter++) {
+ struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
+ if (tb_fmt) {
+ tb_fmt->count++;
+ *iter = tb_fmt->fmt;
+ continue;
+ }
+
+ tb_fmt = kmalloc(offsetof(struct trace_bprintk_fmt, fmt)
+ + strlen(*iter) + 1, GFP_KERNEL);
+ if (tb_fmt) {
+ list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
+ tb_fmt->count = 1;
+ strcpy(tb_fmt->fmt, *iter);
+ *iter = tb_fmt->fmt;
+ } else
+ *iter = NULL;
+ }
+ unlock_btrace();
+}
+
+static
+void release_module_trace_bprintk_format(const char **start, const char **end)
+{
+ const char **iter;
+ lock_btrace();
+ for (iter = start; iter < end; iter++) {
+ struct trace_bprintk_fmt *tb_fmt;
+ if (!*iter)
+ continue;
+
+ tb_fmt = container_of(*iter, struct trace_bprintk_fmt, fmt[0]);
+ tb_fmt->count--;
+ if (!tb_fmt->count && !btrace_metadata_count) {
+ list_del(&tb_fmt->list);
+ kfree(tb_fmt);
+ }
+ }
+ unlock_btrace();
+}
+
+static int module_trace_bprintk_format_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct module *mod = data;
+ if (mod->num_trace_bprintk_fmt) {
+ const char **start = mod->trace_bprintk_fmt_start;
+ const char **end = start + mod->num_trace_bprintk_fmt;
+
+ if (val == MODULE_STATE_COMING)
+ hold_module_trace_bprintk_format(start, end);
+ else if (val == MODULE_STATE_GOING)
+ release_module_trace_bprintk_format(start, end);
+ }
+ return 0;
+}
+
static void get_btrace_metadata(void)
{
lock_btrace();
@@ -44,9 +145,31 @@ static void put_btrace_metadata(void)
{
lock_btrace();
btrace_metadata_count--;
+
+ if (!btrace_metadata_count) {
+ shrink_trace_bprintk_fmt();
+ }
unlock_btrace();
}

+#else /* !CONFIG_MODULES */
+__init static int
+module_trace_bprintk_format_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ return 0;
+}
+
+static inline void get_btrace_metadata(void) { }
+static inline void put_btrace_metadata(void) { }
+#endif /* CONFIG_MODULES */
+
+
+__initdata_or_module static
+struct notifier_block module_trace_bprintk_format_nb = {
+ .notifier_call = module_trace_bprintk_format_notify,
+};
+
/* events tracer */
int trace_bprintk_enable;

@@ -81,7 +204,14 @@ static struct tracer bprintk_trace __read_mostly =

static __init int init_bprintk(void)
{
- return register_tracer(&bprintk_trace);
+ int ret = register_module_notifier(&module_trace_bprintk_format_nb);
+ if (ret)
+ return ret;
+
+ ret = register_tracer(&bprintk_trace);
+ if (ret)
+ unregister_module_notifier(&module_trace_bprintk_format_nb);
+ return ret;
}

device_initcall(init_bprintk);
--
1.6.1



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