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NAME | SYNOPSIS | DESCRIPTION | API | EXAMPLE | SEE ALSO | COLOPHON |
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PERF-DLFILTER(1) perf Manual PERF-DLFILTER(1)
perf-dlfilter - Filter sample events using a dynamically loaded
shared object file
perf script [--dlfilter file.so ] [ --dlarg arg ]...
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.
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,
};
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
perf-script(1)
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)
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