On Sat, Nov 26, 2016 at 07:03:49AM +0000, Wang Nan wrote:
> Newly introduced jit-helpers.[ch] defines a series of helpers which helps
> jitted perf hook functions accessing BPF maps defined in their BPF scripts.
> The helpers fetches fd of 'struct bpf_map' from 'struct bpf_object' and the
> address of 'struct bpf_map_def' in jitted file. 'struct bpf_object' is the
> context passed to hooks.
>
> Jit helpers added in this commits are all leading with 'perf_'. We don't use
> 'bpf_' prefix because in following commits 'bpf_' prefix is going to be
> assigned
> to kernel side BPF map operations. Same operation has different protocol for
> kernel and user.
>
> Example:
>
> $ cat ./test.c
> /*******************************************************/
> #define SEC(name) __attribute__((section(name), used))
> #define BPF_MAP_TYPE_ARRAY 2
> #define BPF_MAP_TYPE_PERF_EVENT_ARRAY 4
> #define BPF_FUNC_map_lookup_elem 1
> static void *(*bpf_map_lookup_elem)(void *map, void *key) =
> (void *) BPF_FUNC_map_lookup_elem;
> struct bpf_map_def {
> unsigned int type;
> unsigned int key_size;
> unsigned int value_size;
> unsigned int max_entries;
> };
> struct bpf_map_def SEC("maps") counter = {
> .type = BPF_MAP_TYPE_ARRAY,
> .key_size = sizeof(int),
> .value_size = sizeof(int),
> .max_entries = 1,
> };
> extern int perf_map_update_elem(void *ctx, struct bpf_map_def *map,
> void *key, void *value, unsigned long flags);
> extern int perf_map_lookup_elem(void *ctx, struct bpf_map_def *map,
> void *key, void *value);
> SEC("sys_close=SyS_close")
> int sys_close(void *ctx)
> {
> int key = 0;
> int *value;
> value = bpf_map_lookup_elem(&counter, &key);
> if (!value)
> return 0;
> __sync_fetch_and_add(value, 1);
> return 0;
> }
> extern int printf(const char *fmt, ...);
> SEC("perfhook:record_start")
> void record_start(void *ctx)
> {
> int key = 0;
> int value = 100000000;
> printf("Welcom to perf record\n");
> perf_map_update_elem(ctx, &counter, &key, &value, 0);
> }
>
> SEC("perfhook:record_end")
> void record_end(void *ctx)
> {
> int key = 0;
> int value;
> perf_map_lookup_elem(ctx, &counter, &key, &value);
> printf("Goodbye, perf record, value=%d\n", value);
> }
> char _license[] SEC("license") = "GPL";
> int _version SEC("version") = LINUX_VERSION_CODE;
> /*******************************************************/
> $ sudo perf record -e ./test.c echo Hehe
> Welcom to perf record
> Hehe
> [ perf record: Woken up 1 times to write data ]
> Goodbye, perf record, value=100000644
> [ perf record: Captured and wrote 0.014 MB perf.data ]
>
> Signed-off-by: Wang Nan <wangn...@huawei.com>
...
> +#define __stringify_1(x) #x
> +#define __stringify(x) __stringify_1(x)
> static std::map<const std::string, const void *> exported_funcs =
> {
> -#define EXPORT(f) {#f, (const void *)&f}
> +#define EXPORT(f) {__stringify(f), (const void *)&f}
> EXPORT(test__clang_callback),
> EXPORT(printf),
> EXPORT(puts),
> + EXPORT(JIT_HELPER_FUNC_NAME(map_update_elem)),
> + EXPORT(JIT_HELPER_FUNC_NAME(map_lookup_elem)),
> + EXPORT(JIT_HELPER_FUNC_NAME(map_get_next_key)),
> + EXPORT(JIT_HELPER_FUNC_NAME(map_pin)),
> #undef EXPORT
...
> +#define PARAMS(args...) args
> +#define DEFINE_JIT_BPF_MAP_HELPER(name, proto, args) \
> + JIT_BPF_MAP_HELPER(name, proto) { \
> + int map_fd = get_bpf_map_fd(ctx, map); \
> + \
> + if (map_fd < 0) \
> + return map_fd; \
> + return bpf_map_##name(map_fd, args); \
> + }
> +
> +DEFINE_JIT_BPF_MAP_HELPER(update_elem,
> + PARAMS(void *key, void *value, u64 flags),
> + PARAMS(key, value, flags))
the naming and approach to exports look good to me.
Acked-by: Alexei Starovoitov <a...@kernel.org>
