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Date: Mon, 2 Mar 2009 11:34:51 -0500 (EST)
From: Steven Rostedt <rostedt@...dmis.org>
To: Frederic Weisbecker <fweisbec@...il.com>
cc: Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Lai Jiangshan <laijs@...fujitsu.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] ftrace: add ftrace_bprintk()
On Sat, 28 Feb 2009, Frederic Weisbecker wrote:
> From: Lai Jiangshan <laijs@...fujitsu.com>
>
> Impact: Add a generic printk() for ftrace, like ftrace_printk()
>
> ftrace_bprintk() use the infrastructure to record events on ring_buffer.
>
> [fweisbec@...il.com: ported to latest -tip and made it work if !CONFIG_MODULES]
>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.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) = .; \
If this can only be done when tracing is enabled, I would wrap that up
in a macro that is a nop when tracing is disabled.
> } \
> \
> .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_MODULE> +
> /* 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);
Shouldn't *iter get assigned to NULL somewhere here?
-- Steve
> + }
> + }
> + 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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