The API for filtering consists of the following:
#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.
Do not assume the sample argument is valid (dereferenceable) after filter_event and filter_event_early
return.
Do not assume data referenced by pointers in struct perf_dlfilter_sample is valid (dereferenceable) after
filter_event and filter_event_early return.
Theperf_dlfilter_samplestructurefilter_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;
__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:
#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
}
Theperf_dlfilter_fnsstructure
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 (*al_cleanup)(void *ctx, struct perf_dlfilter_al *al);
void *(*reserved[119])(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. Call al_cleanup() (if present, see below) when al data is no longer needed.
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.
al_cleanup must be called (if present, so check perf_dlfilter_fns.al_cleanup != NULL) after
resolve_address() to free any associated resources.
Do not assume pointers obtained via perf_dlfilter_fns are valid (dereferenceable) after filter_event and
filter_event_early return.
Theperf_dlfilter_alstructure
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;
void *priv; /* Private data. Do not change */
};
Do not assume data referenced by pointers in struct perf_dlfilter_al is valid (dereferenceable) after
filter_event and filter_event_early return.
perf_dlfilter_sampleflags
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,
};
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