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SubjectRe: [PATCH 2/2] tracing/events: introduce __dynamic_array()

On Mon, 1 Jun 2009, Li Zefan wrote:

> __string() is limited:
>
> - it's a char array, but we may want to define array with other types
> - a source string should be available, but we may just know the string size
>
> We introduce __dynamic_array() to break those limitations, and __string()
> becomes a wrapper of it. As a side effect, now __get_str() can be used
> in TP_fast_assign but not only TP_print.
>
> Take XFS for example, we have the string length in the dirent, but the
> string itself is not NULL-terminated, so __dynamic_array() can be used:
>
> TRACE_EVENT(xfs_dir2,
> TP_PROTO(struct xfs_da_args *args),
> TP_ARGS(args),
>
> TP_STRUCT__entry(
> __field(int, namelen)
> __dynamic_array(char, name, args->namelen + 1)
> ...
> ),
>
> TP_fast_assign(
> char *name = __get_str(name);
>
> if (args->namelen)
> memcpy(name, args->name, args->namelen);
> name[args->namelen] = '\0';
>
> __entry->namelen = args->namelen;
> ),
>
> TP_printk("name %.*s namelen %d",
> __entry->namelen ? __get_str(name) : NULL
> __entry->namelen)
> );
>
> [ Impact: allow defining dynamic size arrays ]
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

Thanks Li,

I'll pull this in.

-- Steve

> ---
> include/trace/ftrace.h | 122 ++++++++++++++++++++++++++----------
> kernel/trace/trace_events_filter.c | 6 +-
> 2 files changed, 91 insertions(+), 37 deletions(-)
>
> diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> index ee92682..b5478da 100644
> --- a/include/trace/ftrace.h
> +++ b/include/trace/ftrace.h
> @@ -18,14 +18,17 @@
>
> #include <linux/ftrace_event.h>
>
> +#undef __field
> +#define __field(type, item) type item;
> +
> #undef __array
> #define __array(type, item, len) type item[len];
>
> -#undef __field
> -#define __field(type, item) type item;
> +#undef __dynamic_array
> +#define __dynamic_array(type, item, len) unsigned short __data_loc_##item;
>
> #undef __string
> -#define __string(item, src) unsigned short __str_loc_##item;
> +#define __string(item, src) __dynamic_array(char, item, -1)
>
> #undef TP_STRUCT__entry
> #define TP_STRUCT__entry(args...) args
> @@ -35,7 +38,7 @@
> struct ftrace_raw_##name { \
> struct trace_entry ent; \
> tstruct \
> - char __str_data[0]; \
> + char __data[0]; \
> }; \
> static struct ftrace_event_call event_##name
>
> @@ -47,30 +50,31 @@
> *
> * Include the following:
> *
> - * struct ftrace_str_offsets_<call> {
> - * int <str1>;
> - * int <str2>;
> + * struct ftrace_data_offsets_<call> {
> + * int <item1>;
> + * int <item2>;
> * [...]
> * };
> *
> - * The __string() macro will create each int <str>, this is to
> - * keep the offset of each string from the beggining of the event
> - * once we perform the strlen() of the src strings.
> - *
> + * The __dynamic_array() macro will create each int <item>, this is
> + * to keep the offset of each array from the beginning of the event.
> */
>
> +#undef __field
> +#define __field(type, item);
> +
> #undef __array
> #define __array(type, item, len)
>
> -#undef __field
> -#define __field(type, item);
> +#undef __dynamic_array
> +#define __dynamic_array(type, item, len) int item;
>
> #undef __string
> -#define __string(item, src) int item;
> +#define __string(item, src) __dynamic_array(char, item, -1)
>
> #undef TRACE_EVENT
> #define TRACE_EVENT(call, proto, args, tstruct, assign, print) \
> - struct ftrace_str_offsets_##call { \
> + struct ftrace_data_offsets_##call { \
> tstruct; \
> };
>
> @@ -119,8 +123,12 @@
> #undef TP_printk
> #define TP_printk(fmt, args...) fmt "\n", args
>
> +#undef __get_dynamic_array
> +#define __get_dynamic_array(field) \
> + ((void *)__entry + __entry->__data_loc_##field)
> +
> #undef __get_str
> -#define __get_str(field) ((char *)__entry + __entry->__str_loc_##field)
> +#define __get_str(field) (char *)__get_dynamic_array(field)
>
> #undef __print_flags
> #define __print_flags(flag, delim, flag_array...) \
> @@ -207,16 +215,19 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \
> if (!ret) \
> return 0;
>
> -#undef __string
> -#define __string(item, src) \
> - ret = trace_seq_printf(s, "\tfield:__str_loc " #item ";\t" \
> +#undef __dynamic_array
> +#define __dynamic_array(type, item, len) \
> + ret = trace_seq_printf(s, "\tfield:__data_loc " #item ";\t" \
> "offset:%u;\tsize:%u;\n", \
> (unsigned int)offsetof(typeof(field), \
> - __str_loc_##item), \
> - (unsigned int)sizeof(field.__str_loc_##item)); \
> + __data_loc_##item), \
> + (unsigned int)sizeof(field.__data_loc_##item)); \
> if (!ret) \
> return 0;
>
> +#undef __string
> +#define __string(item, src) __dynamic_array(char, item, -1)
> +
> #undef __entry
> #define __entry REC
>
> @@ -260,11 +271,14 @@ ftrace_format_##call(struct trace_seq *s) \
> if (ret) \
> return ret;
>
> +#undef __dynamic_array
> +#define __dynamic_array(type, item, len) \
> + ret = trace_define_field(event_call, "__data_loc" "[" #type "]", #item,\
> + offsetof(typeof(field), __data_loc_##item), \
> + sizeof(field.__data_loc_##item), 0);
> +
> #undef __string
> -#define __string(item, src) \
> - ret = trace_define_field(event_call, "__str_loc", #item, \
> - offsetof(typeof(field), __str_loc_##item), \
> - sizeof(field.__str_loc_##item), 0);
> +#define __string(item, src) __dynamic_array(char, item, -1)
>
> #undef TRACE_EVENT
> #define TRACE_EVENT(call, proto, args, tstruct, func, print) \
> @@ -289,6 +303,43 @@ ftrace_define_fields_##call(void) \
> #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
>
> /*
> + * remember the offset of each array from the beginning of the event.
> + */
> +
> +#undef __entry
> +#define __entry entry
> +
> +#undef __field
> +#define __field(type, item)
> +
> +#undef __array
> +#define __array(type, item, len)
> +
> +#undef __dynamic_array
> +#define __dynamic_array(type, item, len) \
> + __data_offsets->item = __data_size + \
> + offsetof(typeof(*entry), __data); \
> + __data_size += (len) * sizeof(type);
> +
> +#undef __string
> +#define __string(item, src) __dynamic_array(char, item, strlen(src) + 1) \
> +
> +#undef TRACE_EVENT
> +#define TRACE_EVENT(call, proto, args, tstruct, assign, print) \
> +static inline int ftrace_get_offsets_##call( \
> + struct ftrace_data_offsets_##call *__data_offsets, proto) \
> +{ \
> + int __data_size = 0; \
> + struct ftrace_raw_##call __maybe_unused *entry; \
> + \
> + tstruct; \
> + \
> + return __data_size; \
> +}
> +
> +#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
> +
> +/*
> * Stage 4 of the trace events.
> *
> * Override the macros in <trace/trace_events.h> to include the following:
> @@ -432,15 +483,15 @@ static void ftrace_profile_disable_##call(struct ftrace_event_call *event_call)\
> #undef __array
> #define __array(type, item, len)
>
> +#undef __dynamic_array
> +#define __dynamic_array(type, item, len) \
> + __entry->__data_loc_##item = __data_offsets.item;
> +
> #undef __string
> -#define __string(item, src) \
> - __str_offsets.item = __str_size + \
> - offsetof(typeof(*entry), __str_data); \
> - __str_size += strlen(src) + 1;
> +#define __string(item, src) __dynamic_array(char, item, -1) \
>
> #undef __assign_str
> #define __assign_str(dst, src) \
> - __entry->__str_loc_##dst = __str_offsets.dst; \
> strcpy(__get_str(dst), src);
>
> #undef TRACE_EVENT
> @@ -451,26 +502,29 @@ static struct ftrace_event_call event_##call; \
> \
> static void ftrace_raw_event_##call(proto) \
> { \
> - struct ftrace_str_offsets_##call __maybe_unused __str_offsets; \
> + struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
> struct ftrace_event_call *event_call = &event_##call; \
> struct ring_buffer_event *event; \
> struct ftrace_raw_##call *entry; \
> unsigned long irq_flags; \
> - int __str_size = 0; \
> + int __data_size; \
> int pc; \
> \
> local_save_flags(irq_flags); \
> pc = preempt_count(); \
> \
> - tstruct; \
> + __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
> \
> event = trace_current_buffer_lock_reserve(event_##call.id, \
> - sizeof(struct ftrace_raw_##call) + __str_size,\
> + sizeof(*entry) + __data_size, \
> irq_flags, pc); \
> if (!event) \
> return; \
> entry = ring_buffer_event_data(event); \
> \
> + \
> + tstruct \
> + \
> { assign; } \
> \
> if (!filter_current_check_discard(event_call, entry, event)) \
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 35d10df..ffd461a 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -478,12 +478,12 @@ enum {
>
> static int is_string_field(const char *type)
> {
> + if (strstr(type, "__data_loc") && strstr(type, "char"))
> + return FILTER_DYN_STRING;
> +
> if (strchr(type, '[') && strstr(type, "char"))
> return FILTER_STATIC_STRING;
>
> - if (!strcmp(type, "__str_loc"))
> - return FILTER_DYN_STRING;
> -
> return 0;
> }
>
> --
> 1.5.4.rc3
>
>
>


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