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SubjectRe: [PATCH 2/2] tracing/events: record the size of dynamic arrays
On Thu, Jul 16, 2009 at 10:54:02AM +0800, Li Zefan wrote:
> When a dynamic array is defined, we add __data_loc_foo in
> trace_entry to record the offset of the array, but the
> size of the array is not recorded, which causes 2 problems:
>
> - the event filter just compares the first 2 chars of the strings.
>
> - parsers can't parse dynamic arrays.
>
> So we encode the size of each dynamic array in the higher 16 bits
> of __data_loc_foo, while the offset is in lower 16 bits.
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
> include/trace/ftrace.h | 14 ++++++++------
> kernel/trace/trace_events_filter.c | 6 ++++--
> 2 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> index cc78943..3cbb96e 100644
> --- a/include/trace/ftrace.h
> +++ b/include/trace/ftrace.h
> @@ -25,7 +25,7 @@
> #define __array(type, item, len) type item[len];
>
> #undef __dynamic_array
> -#define __dynamic_array(type, item, len) unsigned short __data_loc_##item;
> +#define __dynamic_array(type, item, len) u32 __data_loc_##item;
>
> #undef __string
> #define __string(item, src) __dynamic_array(char, item, -1)
> @@ -51,13 +51,14 @@
> * Include the following:
> *
> * struct ftrace_data_offsets_<call> {
> - * int <item1>;
> - * int <item2>;
> + * u32 <item1>;
> + * u32 <item2>;
> * [...]
> * };
> *
> - * The __dynamic_array() macro will create each int <item>, this is
> + * The __dynamic_array() macro will create each u32 <item>, this is
> * to keep the offset of each array from the beginning of the event.
> + * The size of an array is also encoded, in the higher 16 bits of <item>.
> */
>
> #undef __field
> @@ -67,7 +68,7 @@
> #define __array(type, item, len)
>
> #undef __dynamic_array
> -#define __dynamic_array(type, item, len) int item;
> +#define __dynamic_array(type, item, len) u32 item;
>
> #undef __string
> #define __string(item, src) __dynamic_array(char, item, -1)
> @@ -207,7 +208,7 @@ ftrace_format_##call(struct trace_seq *s) \
>
> #undef __get_dynamic_array
> #define __get_dynamic_array(field) \
> - ((void *)__entry + __entry->__data_loc_##field)
> + ((void *)__entry + (__entry->__data_loc_##field & 0xffff))
>
> #undef __get_str
> #define __get_str(field) (char *)__get_dynamic_array(field)
> @@ -325,6 +326,7 @@ ftrace_define_fields_##call(void) \
> #define __dynamic_array(type, item, len) \
> __data_offsets->item = __data_size + \
> offsetof(typeof(*entry), __data); \
> + __data_offsets->item |= (len * sizeof(type)) << 16; \
> __data_size += (len) * sizeof(type);
>
> #undef __string
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index b9aae72..1c80ef7 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -176,11 +176,13 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
> static int filter_pred_strloc(struct filter_pred *pred, void *event,
> int val1, int val2)
> {
> - unsigned short str_loc = *(unsigned short *)(event + pred->offset);
> + u32 str_item = *(u32 *)(event + pred->offset);
> + int str_loc = str_item & 0xffff;
> + int str_len = str_item >> 16;
> char *addr = (char *)(event + str_loc);
> int cmp, match;
>
> - cmp = strncmp(addr, pred->str_val, pred->str_len);
> + cmp = strncmp(addr, pred->str_val, str_len);
>
> match = (!cmp) ^ pred->not;
>
> -- 1.6.3


Looks good.
Like the previous one, I prefer to wait for an Ack from Steve though.



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