perf-dlfilter - Man Page

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;
        __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
}

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.

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.

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,
};