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    Subject[PATCH 3/3] 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 make it work if !CONFIG_MODULES]

    Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    ---
    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 5406e70..d52af50 100644
    --- a/include/asm-generic/vmlinux.lds.h
    +++ b/include/asm-generic/vmlinux.lds.h
    @@ -91,6 +91,9 @@
    *(__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 22d7379..2dece10 100644
    --- a/kernel/module.c
    +++ b/kernel/module.c
    @@ -2158,6 +2158,12 @@ 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 be0bb8c..10173a0 100644
    --- a/kernel/trace/trace.c
    +++ b/kernel/trace/trace.c
    @@ -3140,6 +3140,21 @@ 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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