Messages in this thread | | | Subject | Re: [PATCH v4 09/16] perf tools: Enable indices setting syntax for BPF maps | From | pi3orama <> | Date | Fri, 11 Dec 2015 20:39:35 +0800 |
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发自我的 iPhone
> 在 2015年12月11日,下午8:15,Arnaldo Carvalho de Melo <acme@kernel.org> 写道: > > Em Fri, Dec 11, 2015 at 09:11:45AM -0300, Arnaldo Carvalho de Melo escreveu: >> Em Tue, Dec 08, 2015 at 02:25:37AM +0000, Wang Nan escreveu: >>> This patch introduce a new syntax to perf event parser: >>> >>> # perf record -e bpf_file.c/maps.mymap.value[0,3...5,7]=1234/ ... >> >> Is the above example valid? Wouldn't this be "maps:mymap.value" ? >> >>> >>> By utilizing the basic facilities in bpf-loader.c which allow setting >>> different slots in a BPF map separately, the newly introduced syntax >>> allows perf to control specific elements in a BPF map. >>> >>> Test result: >>> >>> # cat ./test_bpf_map_3.c >>> /************************ BEGIN **************************/ >>> #define SEC(NAME) __attribute__((section(NAME), used)) >>> enum bpf_map_type { >>> BPF_MAP_TYPE_ARRAY = 2, >>> }; >>> struct bpf_map_def { >>> unsigned int type; >>> unsigned int key_size; >>> unsigned int value_size; >>> unsigned int max_entries; >>> }; >>> static void *(*map_lookup_elem)(struct bpf_map_def *, void *) = >>> (void *)1; >>> static int (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = >>> (void *)6; >> >> Can you explain the above a bit more? What are the magic 1 and 6 values? > > So, from another patch: > > static u64 (*bpf_ktime_get_ns)(void) = > (void *)5; > static int (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = > (void *)6; > static int (*bpf_get_smp_processor_id)(void) = > (void *)8; > static int (*bpf_perf_event_output)(void *, struct bpf_map_def *, int, > void *, unsigned long) = > (void *)23; > > Where can I get this magical mistery table? Could this be hidden away in > some .h file automagically included in bpf scriptlets so that n00bies > like me don't have to be wtf'ing? >
They are function numbers defined in bpf.h and bpf-common.h, but they are Linux headers. Directly include them causes many error for llvm. Also, the function prototypes are BPF specific and can't included in Linux source. We should have a place holds those indices and prototypes together.
> - Arnaldo
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