'\" t .\" Title: perf-dlfilter .\" Author: [see the "AUTHOR(S)" section] .\" Generator: Asciidoctor 2.0.16 .\" Date: 2021-11-03 .\" Manual: perf Manual .\" Source: perf .\" Language: English .\" .TH "PERF_5.14\-DLFILTER" "1" "2021-11-03" "perf" "perf Manual" .ie \n(.g .ds Aq \(aq .el .ds Aq ' .ss \n[.ss] 0 .nh .ad l .de URL \fI\\$2\fP <\\$1>\\$3 .. .als MTO URL .if \n[.g] \{\ . mso www.tmac . am URL . ad l . . . am MTO . ad l . . . LINKSTYLE blue R < > .\} .SH "NAME" perf-dlfilter \- Filter sample events using a dynamically loaded shared object file .SH "SYNOPSIS" .sp .nf \fIperf script\fP [\-\-dlfilter file.so ] [ \-\-dlarg arg ]... .fi .br .SH "DESCRIPTION" .sp 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(). .sp If \fIfile.so\fP 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. .SH "API" .sp The API for filtering consists of the following: .sp .if n .RS 4 .nf .fam C #include 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); .fam .fi .if n .RE .sp If implemented, \fIstart\fP will be called at the beginning, before any calls to \fIfilter_event\fP or \fIfilter_event_early\fP. Return 0 to indicate success, or return a negative error code. \fI*data\fP can be assigned for use by other functions. \fIctx\fP is needed for calls to perf_dlfilter_fns, but most perf_dlfilter_fns are not valid when called from \fIstart\fP. .sp If implemented, \fIstop\fP will be called at the end, after any calls to \fIfilter_event\fP or \fIfilter_event_early\fP. Return 0 to indicate success, or return a negative error code. \fIdata\fP is set by \fIstart\fP. \fIctx\fP is needed for calls to perf_dlfilter_fns, but most perf_dlfilter_fns are not valid when called from \fIstop\fP. .sp If implemented, \fIfilter_event\fP 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. \fIdata\fP is set by \fIstart\fP. \fIctx\fP is needed for calls to \fIperf_dlfilter_fns\fP. .sp \fIfilter_event_early\fP is the same as \fIfilter_event\fP except it is called before internal filtering. .sp If implemented, \fIfilter_description\fP should return a one\-line description of the filter, and optionally a longer description. .SS "The perf_dlfilter_sample structure" .sp \fIfilter_event\fP and \fIfilter_event_early\fP are passed a perf_dlfilter_sample structure, which contains the following fields: .sp .if n .RS 4 .nf .fam C /* * perf sample event information (as per perf script and ) */ struct perf_dlfilter_sample { __u32 size; /* Size of this structure (for compatibility checking) */ __u16 ins_lat; /* Refer PERF_SAMPLE_WEIGHT_TYPE in */ __u16 p_stage_cyc; /* Refer PERF_SAMPLE_WEIGHT_TYPE in */ __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 */ __u64 transaction; /* Refer PERF_SAMPLE_TRANSACTION in */ __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 */ __u64 phys_addr; /* Refer PERF_SAMPLE_PHYS_ADDR in */ __u64 data_page_size; /* Refer PERF_SAMPLE_DATA_PAGE_SIZE in */ __u64 code_page_size; /* Refer PERF_SAMPLE_CODE_PAGE_SIZE in */ __u64 cgroup; /* Refer PERF_SAMPLE_CGROUP in */ __u8 cpumode; /* Refer CPUMODE_MASK etc in */ __u8 addr_correlates_sym; /* True => resolve_addr() can be called */ __u16 misc; /* Refer perf_event_header in */ __u32 raw_size; /* Refer PERF_SAMPLE_RAW in */ const void *raw_data; /* Refer PERF_SAMPLE_RAW in */ __u64 brstack_nr; /* Number of brstack entries */ const struct perf_branch_entry *brstack; /* Refer */ __u64 raw_callchain_nr; /* Number of raw_callchain entries */ const __u64 *raw_callchain; /* Refer */ const char *event; }; .fam .fi .if n .RE .SS "The perf_dlfilter_fns structure" .sp The \fIperf_dlfilter_fns\fP structure is populated with function pointers when the file is loaded. The functions can be called by \fIfilter_event\fP or \fIfilter_event_early\fP. .sp .if n .RS 4 .nf .fam 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 *); }; .fam .fi .if n .RE .sp \fIresolve_ip\fP returns information about ip. .sp \fIresolve_addr\fP returns information about addr (if addr_correlates_sym). .sp \fIargs\fP returns arguments from \-\-dlarg options. .sp \fIresolve_address\fP provides information about \fIaddress\fP. al\(->size must be set before calling. Returns 0 on success, \-1 otherwise. .sp \fIinsn\fP returns instruction bytes and length. .sp \fIsrcline\fP return source file name and line number. .sp \fIattr\fP returns perf_event_attr, refer . .sp \fIobject_code\fP reads object code and returns the number of bytes read. .SS "The perf_dlfilter_al structure" .sp The \fIperf_dlfilter_al\fP structure contains information about an address. .sp .if n .RS 4 .nf .fam 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 */ __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; }; .fam .fi .if n .RE .SS "perf_dlfilter_sample flags" .sp The \fIflags\fP member of \fIperf_dlfilter_sample\fP corresponds with the flags field of perf script. The bits of the flags are as follows: .sp .if n .RS 4 .nf .fam 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, }; .fam .fi .if n .RE .SH "EXAMPLE" .sp Filter out everything except branches from "foo" to "bar": .sp .if n .RS 4 .nf .fam C #include #include 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; } .fam .fi .if n .RE .sp To build the shared object, assuming perf has been installed for the local user i.e. perf_dlfilter.h is in ~/include/perf : .sp .if n .RS 4 .nf .fam C gcc \-c \-I ~/include \-fpic dlfilter\-example.c gcc \-shared \-o dlfilter\-example.so dlfilter\-example.o .fam .fi .if n .RE .sp To use the filter with perf script: .sp .if n .RS 4 .nf .fam C perf script \-\-dlfilter dlfilter\-example.so .fam .fi .if n .RE .SH "SEE ALSO" .sp perf\-script(1)