perf-dlfilter(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | API | EXAMPLE | SEE ALSO | COLOPHON

PERF-DLFILTER(1)               perf Manual              PERF-DLFILTER(1)

NAME         top

       perf-dlfilter - Filter sample events using a dynamically loaded
       shared object file

SYNOPSIS         top

       perf script [--dlfilter file.so ] [ --dlarg arg ]...

DESCRIPTION         top

       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         top

       The API for filtering consists of the following:

           #include <perf/perf_dlfilter.h>

           const 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:

           /*
            * 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;
           };

   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.

           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.

           /*
            * 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:

           /* 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         top

       Filter out everything except branches from "foo" to "bar":

           #include <perf/perf_dlfilter.h>
           #include <string.h>

           const 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

SEE ALSO         top

       perf-script(1)

COLOPHON         top

       This page is part of the perf (Performance analysis tools for
       Linux (in Linux source tree)) project.  Information about the
       project can be found at 
       ⟨https://perf.wiki.kernel.org/index.php/Main_Page⟩.  If you have a
       bug report for this manual page, send it to
       linux-kernel@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git⟩
       on 2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-26.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

perf                           2021-07-01               PERF-DLFILTER(1)

Pages that refer to this page: perf-script(1)