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Diffstat (limited to 'tools/perf/Documentation/perf-dlfilter.txt')
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diff --git a/tools/perf/Documentation/perf-dlfilter.txt b/tools/perf/Documentation/perf-dlfilter.txt new file mode 100644 index 000000000000..fb22e3b31dc5 --- /dev/null +++ b/tools/perf/Documentation/perf-dlfilter.txt @@ -0,0 +1,281 @@ +perf-dlfilter(1) +================ + +NAME +---- +perf-dlfilter - Filter sample events using a dynamically loaded shared +object file + +SYNOPSIS +-------- +[verse] +'perf script' [--dlfilter file.so ] [ --dlarg arg ]... + +DESCRIPTION +----------- + +This option is used to process data through a custom filter provided by a +dynamically loaded shared object file. Arguments can be passed using --dlarg +and retrieved using perf_dlfilter_fns.args(). + +If 'file.so' does not contain "/", then it will be found either in the current +directory, or perf tools exec path which is ~/libexec/perf-core/dlfilters for +a local build and install (refer perf --exec-path), or the dynamic linker +paths. + +API +--- + +The API for filtering consists of the following: + +[source,c] +---- +#include <perf/perf_dlfilter.h> + +struct perf_dlfilter_fns perf_dlfilter_fns; + +int start(void **data, void *ctx); +int stop(void *data, void *ctx); +int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ctx); +int filter_event_early(void *data, const struct perf_dlfilter_sample *sample, void *ctx); +const char *filter_description(const char **long_description); +---- + +If implemented, 'start' will be called at the beginning, before any +calls to 'filter_event' or 'filter_event_early'. Return 0 to indicate success, +or return a negative error code. '*data' can be assigned for use by other +functions. 'ctx' is needed for calls to perf_dlfilter_fns, but most +perf_dlfilter_fns are not valid when called from 'start'. + +If implemented, 'stop' will be called at the end, after any calls to +'filter_event' or 'filter_event_early'. Return 0 to indicate success, or +return a negative error code. 'data' is set by 'start'. 'ctx' is needed +for calls to perf_dlfilter_fns, but most perf_dlfilter_fns are not valid +when called from 'stop'. + +If implemented, 'filter_event' will be called for each sample event. +Return 0 to keep the sample event, 1 to filter it out, or return a negative +error code. 'data' is set by 'start'. 'ctx' is needed for calls to +'perf_dlfilter_fns'. + +'filter_event_early' is the same as 'filter_event' except it is called before +internal filtering. + +If implemented, 'filter_description' should return a one-line description +of the filter, and optionally a longer description. + +The perf_dlfilter_sample structure +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +'filter_event' and 'filter_event_early' are passed a perf_dlfilter_sample +structure, which contains the following fields: +[source,c] +---- +/* + * perf sample event information (as per perf script and <linux/perf_event.h>) + */ +struct perf_dlfilter_sample { + __u32 size; /* Size of this structure (for compatibility checking) */ + __u16 ins_lat; /* Refer PERF_SAMPLE_WEIGHT_TYPE in <linux/perf_event.h> */ + __u16 p_stage_cyc; /* Refer PERF_SAMPLE_WEIGHT_TYPE in <linux/perf_event.h> */ + __u64 ip; + __s32 pid; + __s32 tid; + __u64 time; + __u64 addr; + __u64 id; + __u64 stream_id; + __u64 period; + __u64 weight; /* Refer PERF_SAMPLE_WEIGHT_TYPE in <linux/perf_event.h> */ + __u64 transaction; /* Refer PERF_SAMPLE_TRANSACTION in <linux/perf_event.h> */ + __u64 insn_cnt; /* For instructions-per-cycle (IPC) */ + __u64 cyc_cnt; /* For instructions-per-cycle (IPC) */ + __s32 cpu; + __u32 flags; /* Refer PERF_DLFILTER_FLAG_* above */ + __u64 data_src; /* Refer PERF_SAMPLE_DATA_SRC in <linux/perf_event.h> */ + __u64 phys_addr; /* Refer PERF_SAMPLE_PHYS_ADDR in <linux/perf_event.h> */ + __u64 data_page_size; /* Refer PERF_SAMPLE_DATA_PAGE_SIZE in <linux/perf_event.h> */ + __u64 code_page_size; /* Refer PERF_SAMPLE_CODE_PAGE_SIZE in <linux/perf_event.h> */ + __u64 cgroup; /* Refer PERF_SAMPLE_CGROUP in <linux/perf_event.h> */ + __u8 cpumode; /* Refer CPUMODE_MASK etc in <linux/perf_event.h> */ + __u8 addr_correlates_sym; /* True => resolve_addr() can be called */ + __u16 misc; /* Refer perf_event_header in <linux/perf_event.h> */ + __u32 raw_size; /* Refer PERF_SAMPLE_RAW in <linux/perf_event.h> */ + const void *raw_data; /* Refer PERF_SAMPLE_RAW in <linux/perf_event.h> */ + __u64 brstack_nr; /* Number of brstack entries */ + const struct perf_branch_entry *brstack; /* Refer <linux/perf_event.h> */ + __u64 raw_callchain_nr; /* Number of raw_callchain entries */ + const __u64 *raw_callchain; /* Refer <linux/perf_event.h> */ + const char *event; + __s32 machine_pid; + __s32 vcpu; +}; +---- + +Note: 'machine_pid' and 'vcpu' are not original members, but were added together later. +'size' can be used to determine their presence at run time. +PERF_DLFILTER_HAS_MACHINE_PID will be defined if they are present at compile time. +For example: +[source,c] +---- +#include <perf/perf_dlfilter.h> +#include <stddef.h> +#include <stdbool.h> + +static inline bool have_machine_pid(const struct perf_dlfilter_sample *sample) +{ +#ifdef PERF_DLFILTER_HAS_MACHINE_PID + return sample->size >= offsetof(struct perf_dlfilter_sample, vcpu) + sizeof(sample->vcpu); +#else + return false; +#endif +} +---- + +The perf_dlfilter_fns structure +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The 'perf_dlfilter_fns' structure is populated with function pointers when the +file is loaded. The functions can be called by 'filter_event' or +'filter_event_early'. + +[source,c] +---- +struct perf_dlfilter_fns { + const struct perf_dlfilter_al *(*resolve_ip)(void *ctx); + const struct perf_dlfilter_al *(*resolve_addr)(void *ctx); + char **(*args)(void *ctx, int *dlargc); + __s32 (*resolve_address)(void *ctx, __u64 address, struct perf_dlfilter_al *al); + const __u8 *(*insn)(void *ctx, __u32 *length); + const char *(*srcline)(void *ctx, __u32 *line_number); + struct perf_event_attr *(*attr)(void *ctx); + __s32 (*object_code)(void *ctx, __u64 ip, void *buf, __u32 len); + void *(*reserved[120])(void *); +}; +---- + +'resolve_ip' returns information about ip. + +'resolve_addr' returns information about addr (if addr_correlates_sym). + +'args' returns arguments from --dlarg options. + +'resolve_address' provides information about 'address'. al->size must be set +before calling. Returns 0 on success, -1 otherwise. + +'insn' returns instruction bytes and length. + +'srcline' return source file name and line number. + +'attr' returns perf_event_attr, refer <linux/perf_event.h>. + +'object_code' reads object code and returns the number of bytes read. + +The perf_dlfilter_al structure +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The 'perf_dlfilter_al' structure contains information about an address. + +[source,c] +---- +/* + * Address location (as per perf script) + */ +struct perf_dlfilter_al { + __u32 size; /* Size of this structure (for compatibility checking) */ + __u32 symoff; + const char *sym; + __u64 addr; /* Mapped address (from dso) */ + __u64 sym_start; + __u64 sym_end; + const char *dso; + __u8 sym_binding; /* STB_LOCAL, STB_GLOBAL or STB_WEAK, refer <elf.h> */ + __u8 is_64_bit; /* Only valid if dso is not NULL */ + __u8 is_kernel_ip; /* True if in kernel space */ + __u32 buildid_size; + __u8 *buildid; + /* Below members are only populated by resolve_ip() */ + __u8 filtered; /* true if this sample event will be filtered out */ + const char *comm; +}; +---- + +perf_dlfilter_sample flags +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The 'flags' member of 'perf_dlfilter_sample' corresponds with the flags field +of perf script. The bits of the flags are as follows: + +[source,c] +---- +/* Definitions for perf_dlfilter_sample flags */ +enum { + PERF_DLFILTER_FLAG_BRANCH = 1ULL << 0, + PERF_DLFILTER_FLAG_CALL = 1ULL << 1, + PERF_DLFILTER_FLAG_RETURN = 1ULL << 2, + PERF_DLFILTER_FLAG_CONDITIONAL = 1ULL << 3, + PERF_DLFILTER_FLAG_SYSCALLRET = 1ULL << 4, + PERF_DLFILTER_FLAG_ASYNC = 1ULL << 5, + PERF_DLFILTER_FLAG_INTERRUPT = 1ULL << 6, + PERF_DLFILTER_FLAG_TX_ABORT = 1ULL << 7, + PERF_DLFILTER_FLAG_TRACE_BEGIN = 1ULL << 8, + PERF_DLFILTER_FLAG_TRACE_END = 1ULL << 9, + PERF_DLFILTER_FLAG_IN_TX = 1ULL << 10, + PERF_DLFILTER_FLAG_VMENTRY = 1ULL << 11, + PERF_DLFILTER_FLAG_VMEXIT = 1ULL << 12, +}; +---- + +EXAMPLE +------- + +Filter out everything except branches from "foo" to "bar": + +[source,c] +---- +#include <perf/perf_dlfilter.h> +#include <string.h> + +struct perf_dlfilter_fns perf_dlfilter_fns; + +int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ctx) +{ + const struct perf_dlfilter_al *al; + const struct perf_dlfilter_al *addr_al; + + if (!sample->ip || !sample->addr_correlates_sym) + return 1; + + al = perf_dlfilter_fns.resolve_ip(ctx); + if (!al || !al->sym || strcmp(al->sym, "foo")) + return 1; + + addr_al = perf_dlfilter_fns.resolve_addr(ctx); + if (!addr_al || !addr_al->sym || strcmp(addr_al->sym, "bar")) + return 1; + + return 0; +} +---- + +To build the shared object, assuming perf has been installed for the local user +i.e. perf_dlfilter.h is in ~/include/perf : + + gcc -c -I ~/include -fpic dlfilter-example.c + gcc -shared -o dlfilter-example.so dlfilter-example.o + +To use the filter with perf script: + + perf script --dlfilter dlfilter-example.so + +NOTES +----- + +The dlfilter .so file will be dependent on shared libraries. If those change, +it may be necessary to rebuild the .so. Also there may be unexpected results +if the .so uses different versions of the shared libraries that perf uses. +Versions can be checked using the ldd command. + +SEE ALSO +-------- +linkperf:perf-script[1] |