1PERF-DLFILTER(1) perf Manual PERF-DLFILTER(1)
2
6 perf-dlfilter - Filter sample events using a dynamically loaded shared
7 object file
8
10 perf script [--dlfilter file.so ] [ --dlarg arg ]...
11
13 This option is used to process data through a custom filter provided by
14 a dynamically loaded shared object file. Arguments can be passed using
15 --dlarg and retrieved using perf_dlfilter_fns.args().
16 If file.so does not contain "/", then it will be found either in the
18 current directory, or perf tools exec path which is
19 ~/libexec/perf-core/dlfilters for a local build and install (refer perf
20 --exec-path), or the dynamic linker paths.
21
23 The API for filtering consists of the following:
24 #include <perf/perf_dlfilter.h>
26 struct perf_dlfilter_fns perf_dlfilter_fns;
28 int start(void **data, void *ctx);
30 int stop(void *data, void *ctx);
31 int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ctx);
32 int filter_event_early(void *data, const struct perf_dlfilter_sample *sample, void *ctx);
33 const char *filter_description(const char **long_description);
34 If implemented, start will be called at the beginning, before any calls
36 to filter_event or filter_event_early. Return 0 to indicate success, or
37 return a negative error code. *data can be assigned for use by other
38 functions. ctx is needed for calls to perf_dlfilter_fns, but most
39 perf_dlfilter_fns are not valid when called from start.
40 If implemented, stop will be called at the end, after any calls to
42 filter_event or filter_event_early. Return 0 to indicate success, or
43 return a negative error code. data is set by start. ctx is needed for
44 calls to perf_dlfilter_fns, but most perf_dlfilter_fns are not valid
45 when called from stop.
46 If implemented, filter_event will be called for each sample event.
48 Return 0 to keep the sample event, 1 to filter it out, or return a
49 negative error code. data is set by start. ctx is needed for calls to
50 perf_dlfilter_fns.
51 filter_event_early is the same as filter_event except it is called
53 before internal filtering.
54 If implemented, filter_description should return a one-line description
56 of the filter, and optionally a longer description.
57 The perf_dlfilter_sample structure
59 filter_event and filter_event_early are passed a perf_dlfilter_sample
60 structure, which contains the following fields:
61 /*
63 * perf sample event information (as per perf script and <linux/perf_event.h>)
64 */
65 struct perf_dlfilter_sample {
66 __u32 size; /* Size of this structure (for compatibility checking) */
67 __u16 ins_lat; /* Refer PERF_SAMPLE_WEIGHT_TYPE in <linux/perf_event.h> */
68 __u16 p_stage_cyc; /* Refer PERF_SAMPLE_WEIGHT_TYPE in <linux/perf_event.h> */
69 __u64 ip;
70 __s32 pid;
71 __s32 tid;
72 __u64 time;
73 __u64 addr;
74 __u64 id;
75 __u64 stream_id;
76 __u64 period;
77 __u64 weight; /* Refer PERF_SAMPLE_WEIGHT_TYPE in <linux/perf_event.h> */
78 __u64 transaction; /* Refer PERF_SAMPLE_TRANSACTION in <linux/perf_event.h> */
79 __u64 insn_cnt; /* For instructions-per-cycle (IPC) */
80 __u64 cyc_cnt; /* For instructions-per-cycle (IPC) */
81 __s32 cpu;
82 __u32 flags; /* Refer PERF_DLFILTER_FLAG_* above */
83 __u64 data_src; /* Refer PERF_SAMPLE_DATA_SRC in <linux/perf_event.h> */
84 __u64 phys_addr; /* Refer PERF_SAMPLE_PHYS_ADDR in <linux/perf_event.h> */
85 __u64 data_page_size; /* Refer PERF_SAMPLE_DATA_PAGE_SIZE in <linux/perf_event.h> */
86 __u64 code_page_size; /* Refer PERF_SAMPLE_CODE_PAGE_SIZE in <linux/perf_event.h> */
87 __u64 cgroup; /* Refer PERF_SAMPLE_CGROUP in <linux/perf_event.h> */
88 __u8 cpumode; /* Refer CPUMODE_MASK etc in <linux/perf_event.h> */
89 __u8 addr_correlates_sym; /* True => resolve_addr() can be called */
90 __u16 misc; /* Refer perf_event_header in <linux/perf_event.h> */
91 __u32 raw_size; /* Refer PERF_SAMPLE_RAW in <linux/perf_event.h> */
92 const void *raw_data; /* Refer PERF_SAMPLE_RAW in <linux/perf_event.h> */
93 __u64 brstack_nr; /* Number of brstack entries */
94 const struct perf_branch_entry *brstack; /* Refer <linux/perf_event.h> */
95 __u64 raw_callchain_nr; /* Number of raw_callchain entries */
96 const __u64 *raw_callchain; /* Refer <linux/perf_event.h> */
97 const char *event;
98 };
99 The perf_dlfilter_fns structure
101 The perf_dlfilter_fns structure is populated with function pointers
102 when the file is loaded. The functions can be called by filter_event or
103 filter_event_early.
104 struct perf_dlfilter_fns {
106 const struct perf_dlfilter_al *(*resolve_ip)(void *ctx);
107 const struct perf_dlfilter_al *(*resolve_addr)(void *ctx);
108 char **(*args)(void *ctx, int *dlargc);
109 __s32 (*resolve_address)(void *ctx, __u64 address, struct perf_dlfilter_al *al);
110 const __u8 *(*insn)(void *ctx, __u32 *length);
111 const char *(*srcline)(void *ctx, __u32 *line_number);
112 struct perf_event_attr *(*attr)(void *ctx);
113 __s32 (*object_code)(void *ctx, __u64 ip, void *buf, __u32 len);
114 void *(*reserved[120])(void *);
115 };
116 resolve_ip returns information about ip.
118 resolve_addr returns information about addr (if addr_correlates_sym).
120 args returns arguments from --dlarg options.
122 resolve_address provides information about address. al→size must be set
124 before calling. Returns 0 on success, -1 otherwise.
125 insn returns instruction bytes and length.
127 srcline return source file name and line number.
129 attr returns perf_event_attr, refer <linux/perf_event.h>.
131 object_code reads object code and returns the number of bytes read.
133 The perf_dlfilter_al structure
135 The perf_dlfilter_al structure contains information about an address.
136 /*
138 * Address location (as per perf script)
139 */
140 struct perf_dlfilter_al {
141 __u32 size; /* Size of this structure (for compatibility checking) */
142 __u32 symoff;
143 const char *sym;
144 __u64 addr; /* Mapped address (from dso) */
145 __u64 sym_start;
146 __u64 sym_end;
147 const char *dso;
148 __u8 sym_binding; /* STB_LOCAL, STB_GLOBAL or STB_WEAK, refer <elf.h> */
149 __u8 is_64_bit; /* Only valid if dso is not NULL */
150 __u8 is_kernel_ip; /* True if in kernel space */
151 __u32 buildid_size;
152 __u8 *buildid;
153 /* Below members are only populated by resolve_ip() */
154 __u8 filtered; /* true if this sample event will be filtered out */
155 const char *comm;
156 };
157 perf_dlfilter_sample flags
159 The flags member of perf_dlfilter_sample corresponds with the flags
160 field of perf script. The bits of the flags are as follows:
161 /* Definitions for perf_dlfilter_sample flags */
163 enum {
164 PERF_DLFILTER_FLAG_BRANCH = 1ULL << 0,
165 PERF_DLFILTER_FLAG_CALL = 1ULL << 1,
166 PERF_DLFILTER_FLAG_RETURN = 1ULL << 2,
167 PERF_DLFILTER_FLAG_CONDITIONAL = 1ULL << 3,
168 PERF_DLFILTER_FLAG_SYSCALLRET = 1ULL << 4,
169 PERF_DLFILTER_FLAG_ASYNC = 1ULL << 5,
170 PERF_DLFILTER_FLAG_INTERRUPT = 1ULL << 6,
171 PERF_DLFILTER_FLAG_TX_ABORT = 1ULL << 7,
172 PERF_DLFILTER_FLAG_TRACE_BEGIN = 1ULL << 8,
173 PERF_DLFILTER_FLAG_TRACE_END = 1ULL << 9,
174 PERF_DLFILTER_FLAG_IN_TX = 1ULL << 10,
175 PERF_DLFILTER_FLAG_VMENTRY = 1ULL << 11,
176 PERF_DLFILTER_FLAG_VMEXIT = 1ULL << 12,
177 };
178
180 Filter out everything except branches from "foo" to "bar":
181 #include <perf/perf_dlfilter.h>
183 #include <string.h>
184 struct perf_dlfilter_fns perf_dlfilter_fns;
186 int filter_event(void *data, const struct perf_dlfilter_sample *sample, void *ctx)
188 {
189 const struct perf_dlfilter_al *al;
190 const struct perf_dlfilter_al *addr_al;
191 if (!sample->ip || !sample->addr_correlates_sym)
193 return 1;
194 al = perf_dlfilter_fns.resolve_ip(ctx);
196 if (!al || !al->sym || strcmp(al->sym, "foo"))
197 return 1;
198 addr_al = perf_dlfilter_fns.resolve_addr(ctx);
200 if (!addr_al || !addr_al->sym || strcmp(addr_al->sym, "bar"))
201 return 1;
202 return 0;
204 }
205 To build the shared object, assuming perf has been installed for the
207 local user i.e. perf_dlfilter.h is in ~/include/perf :
208 gcc -c -I ~/include -fpic dlfilter-example.c
210 gcc -shared -o dlfilter-example.so dlfilter-example.o
211 To use the filter with perf script:
213 perf script --dlfilter dlfilter-example.so
215
217 The dlfilter .so file will be dependent on shared libraries. If those
218 change, it may be necessary to rebuild the .so. Also there may be
219 unexpected results if the .so uses different versions of the shared
220 libraries that perf uses. Versions can be checked using the ldd
221 command.
222
224 perf-script(1)
225perf 11/22/2021 PERF-DLFILTER(1)