From: Steven Rostedt Developers have been asking for the ability in the ftrace event tracer to display names of bits in a flags variable. Instead of printing out c2, it would be easier to read FOO|BAR|GOO, assuming that FOO is bit 1, BAR is bit 6 and GOO is bit 7. Some examples where this would be useful are the state flags in a context switch, kmalloc flags, and even permision flags in accessing files. [ v2 changes include: Frederic Weisbecker's idea of using a mask instead of bits, thus we can output GFP_KERNEL instead of GPF_WAIT|GFP_IO|GFP_FS. Li Zefan's idea of allowing the caller of __print_flags to add their own delimiter (or no delimiter) where we can get for file permissions rwx instead of r|w|x. ] [ v3 changes: Christoph Hellwig's idea of using an array instead of va_args. ] [ Impact: better displaying of flags in trace output ] Signed-off-by: Steven Rostedt --- include/linux/ftrace_event.h | 13 ++++++++++++- include/trace/ftrace.h | 14 ++++++++++++++ kernel/trace/trace_output.c | 38 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 64 insertions(+), 1 deletions(-) diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index bae51dd..4b58cf1 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -3,12 +3,23 @@ #include #include - +#include struct trace_array; struct tracer; struct dentry; +DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq); + +struct trace_print_flags { + unsigned long mask; + const char *name; +}; + +const char *ftrace_print_flags_seq(struct trace_seq *p, const char *delim, + unsigned long flags, + const struct trace_print_flags *flag_array); + /* * The trace entry - the most basic unit of tracing. This is what * is printed in the end as a single line in the trace output, such as: diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h index edb02bc..063d227 100644 --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -87,6 +87,7 @@ * struct trace_seq *s = &iter->seq; * struct ftrace_raw_ *field; <-- defined in stage 1 * struct trace_entry *entry; + * struct trace_seq *p; * int ret; * * entry = iter->ent; @@ -98,7 +99,9 @@ * * field = (typeof(field))entry; * + * p = get_cpu_var(ftrace_event_seq); * ret = trace_seq_printf(s, "\n"); + * put_cpu(); * if (!ret) * return TRACE_TYPE_PARTIAL_LINE; * @@ -119,6 +122,14 @@ #undef __get_str #define __get_str(field) ((char *)__entry + __entry->__str_loc_##field) +#undef __print_flags +#define __print_flags(flag, delim, flag_array...) \ + ({ \ + static const struct trace_print_flags flags[] = \ + { flag_array, { -1, NULL }}; \ + ftrace_print_flags_seq(p, delim, flag, flags); \ + }) + #undef TRACE_EVENT #define TRACE_EVENT(call, proto, args, tstruct, assign, print) \ enum print_line_t \ @@ -127,6 +138,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ struct trace_seq *s = &iter->seq; \ struct ftrace_raw_##call *field; \ struct trace_entry *entry; \ + struct trace_seq *p; \ int ret; \ \ entry = iter->ent; \ @@ -138,7 +150,9 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ \ field = (typeof(field))entry; \ \ + p = &get_cpu_var(ftrace_event_seq); \ ret = trace_seq_printf(s, #call ": " print); \ + put_cpu(); \ if (!ret) \ return TRACE_TYPE_PARTIAL_LINE; \ \ diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 489c0e8..e51bcc0 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -14,6 +14,8 @@ /* must be a power of 2 */ #define EVENT_HASHSIZE 128 +DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq); + static DEFINE_MUTEX(trace_event_mutex); static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly; @@ -212,6 +214,42 @@ int trace_seq_path(struct trace_seq *s, struct path *path) return 0; } +const char * +ftrace_print_flags_seq(struct trace_seq *p, const char *delim, + unsigned long flags, + const struct trace_print_flags *flag_array) +{ + unsigned long mask; + const char *str; + int i; + + trace_seq_init(p); + + for (i = 0; flag_array[i].name && flags; i++) { + + mask = flag_array[i].mask; + if ((flags & mask) != mask) + continue; + + str = flag_array[i].name; + flags &= ~mask; + if (p->len && delim) + trace_seq_puts(p, delim); + trace_seq_puts(p, str); + } + + /* check for left over flags */ + if (flags) { + if (p->len && delim) + trace_seq_puts(p, delim); + trace_seq_printf(p, "0x%lx", flags); + } + + trace_seq_putc(p, 0); + + return p->buffer; +} + #ifdef CONFIG_KRETPROBES static inline const char *kretprobed(const char *name) { -- 1.6.2.4 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/