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While valuable for tracing execution origins, these trailing comments can add considerable visual clutter to the call graph, particularly when examining deeply nested call trees or when synthesising higher-level abstractions. Introduce support for filtering out return address comments from function graph trace output. Provide a standalone --filter-retaddr flag. Key aspects of this implementation: 1. Return address parsing and filtering Implement ftrace_filter_retaddr() in tools/perf/util/ftrace.c to locate return address comments and strip them in-place with memmove(3). Additionally, introduce ftrace_parse_retaddr() to parse caller symbol names and offsets across diverse output styles (standard format, return values, and bracketed addresses), establishing the parsing foundation for subsequent inlined callchain resolution. 2. Command-line interface Expose --filter-retaddr in tools/perf/builtin-ftrace.c, updating the documentation in tools/perf/Documentation/perf-ftrace.txt accordingly. 3. Automated verification Add a dedicated unit test suite ("Ftrace return address processing") in tools/perf/tests/ftrace.c to validate comment parsing and string filtering across all supported formats. Assisted-by: Antigravity:gemini-3.1-pro Signed-off-by: Aaron Tomlin --- tools/perf/Documentation/perf-ftrace.txt | 4 ++ tools/perf/builtin-ftrace.c | 8 +++ tools/perf/tests/Build | 1 + tools/perf/tests/builtin-test.c | 1 + tools/perf/tests/ftrace.c | 80 ++++++++++++++++++++++ tools/perf/tests/tests.h | 1 + tools/perf/util/Build | 1 + tools/perf/util/ftrace.c | 87 ++++++++++++++++++++++++ tools/perf/util/ftrace.h | 5 ++ 9 files changed, 188 insertions(+) create mode 100644 tools/perf/tests/ftrace.c create mode 100644 tools/perf/util/ftrace.c diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt index 3f3808e513fe..e8105083e67c 100644 --- a/tools/perf/Documentation/perf-ftrace.txt +++ b/tools/perf/Documentation/perf-ftrace.txt @@ -134,6 +134,10 @@ OPTIONS for 'perf ftrace trace' - depth= - Set max depth for function graph tracer to follow. - tail - Print function name at the end. +--filter-retaddr:: + Filter out function return address comments (`/* <-caller+offset */`) + from function_graph output. + OPTIONS for 'perf ftrace latency' --------------------------------- diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c index efd5343dc9ad..b8ab76912a0e 100644 --- a/tools/perf/builtin-ftrace.c +++ b/tools/perf/builtin-ftrace.c @@ -828,6 +828,8 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace) break; for (int i = 0; i < n; i++) { if (buf[i] == '\n') { + if (ftrace->filter_retaddr) + ftrace_filter_retaddr(linebuf.buf); if (fprintf(stdout, "%s\n", linebuf.buf) < 0) break; strbuf_setlen(&linebuf, 0); @@ -860,6 +862,8 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace) break; for (int i = 0; i < n; i++) { if (buf[i] == '\n') { + if (ftrace->filter_retaddr) + ftrace_filter_retaddr(linebuf.buf); if (fprintf(stdout, "%s\n", linebuf.buf) < 0) break; strbuf_setlen(&linebuf, 0); @@ -871,6 +875,8 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace) } if (!ferror(stdout) && linebuf.len > 0) { + if (ftrace->filter_retaddr) + ftrace_filter_retaddr(linebuf.buf); fprintf(stdout, "%s\n", linebuf.buf); strbuf_setlen(&linebuf, 0); } @@ -1836,6 +1842,8 @@ int cmd_ftrace(int argc, const char **argv) "Size of per cpu buffer, needs to use a B, K, M or G suffix.", parse_buffer_size), OPT_BOOLEAN(0, "inherit", &ftrace.inherit, "Trace children processes"), + OPT_BOOLEAN_SET(0, "filter-retaddr", &ftrace.filter_retaddr, &ftrace.filter_retaddr_set, + "Filter out funcgraph return address comments"), OPT_INTEGER('D', "delay", &ftrace.target.initial_delay, "Number of milliseconds to wait before starting tracing after program start"), OPT_PARENT(common_options), diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build index 395f2866094a..136138932fcb 100644 --- a/tools/perf/tests/Build +++ b/tools/perf/tests/Build @@ -72,6 +72,7 @@ perf-test-y += hwmon_pmu.o perf-test-y += tool_pmu.o perf-test-y += subcmd-help.o perf-test-y += kallsyms-split.o +perf-test-y += ftrace.o ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 arm arm64 powerpc riscv)) perf-test-$(CONFIG_DWARF_UNWIND) += dwarf-unwind.o diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c index d2f594921e25..9663f48afb92 100644 --- a/tools/perf/tests/builtin-test.c +++ b/tools/perf/tests/builtin-test.c @@ -137,6 +137,7 @@ static struct test_suite *generic_tests[] = { &suite__perf_hooks, &suite__unit_number__scnprint, &suite__mem2node, + &suite__ftrace, &suite__time_utils, &suite__jit_write_elf, &suite__pfm, diff --git a/tools/perf/tests/ftrace.c b/tools/perf/tests/ftrace.c new file mode 100644 index 000000000000..596cecee844e --- /dev/null +++ b/tools/perf/tests/ftrace.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include "tests.h" +#include "debug.h" +#include "util/ftrace.h" + +static int test_parse_retaddr(void) +{ + char sym[128]; + u64 offset = 0; + + /* Standard format */ + TEST_ASSERT_VAL("parse standard retaddr", + ftrace_parse_retaddr("kernel_read() { /* <-load_elf_phdrs+0x6c/0xb0 */", + sym, sizeof(sym), &offset)); + TEST_ASSERT_EQUAL("sym name", strcmp(sym, "load_elf_phdrs"), 0); + TEST_ASSERT_VAL("offset", offset == 0x6c); + + /* With return value */ + TEST_ASSERT_VAL("parse retaddr with ret", + ftrace_parse_retaddr( + "__cond_resched(); /* <-load_elf_phdrs+0x6c/0xb0 ret=0x0 */", + sym, sizeof(sym), &offset)); + TEST_ASSERT_EQUAL("sym name", strcmp(sym, "load_elf_phdrs"), 0); + TEST_ASSERT_VAL("offset", offset == 0x6c); + + /* Bracketed address */ + TEST_ASSERT_VAL("parse bracketed retaddr", + ftrace_parse_retaddr("foo() { /* <-[0xffffffff818534c8] bar+0x20/0x40 */", + sym, sizeof(sym), &offset)); + TEST_ASSERT_EQUAL("sym name", strcmp(sym, "bar"), 0); + TEST_ASSERT_VAL("offset", offset == 0x20); + + /* No return address */ + TEST_ASSERT_VAL("no retaddr", + !ftrace_parse_retaddr("do_filp_open();", sym, sizeof(sym), &offset)); + + return TEST_OK; +} + +static int test_filter_retaddr(void) +{ + char line1[] = "kernel_read() { /* <-load_elf_phdrs+0x6c/0xb0 */"; + char line2[] = "__cond_resched(); /* <-load_elf_phdrs+0x6c/0xb0 ret=0x0 */"; + char line3[] = "do_filp_open();"; + + ftrace_filter_retaddr(line1); + TEST_ASSERT_EQUAL("filter standard retaddr", strcmp(line1, "kernel_read() {"), 0); + + ftrace_filter_retaddr(line2); + TEST_ASSERT_EQUAL("filter retaddr with ret", strcmp(line2, "__cond_resched();"), 0); + + ftrace_filter_retaddr(line3); + TEST_ASSERT_EQUAL("filter line without retaddr unchanged", + strcmp(line3, "do_filp_open();"), 0); + + return TEST_OK; +} + +static int test__ftrace(struct test_suite *test __maybe_unused, int subtest __maybe_unused) +{ + int ret; + + ret = test_parse_retaddr(); + if (ret != TEST_OK) + return ret; + + ret = test_filter_retaddr(); + if (ret != TEST_OK) + return ret; + + return TEST_OK; +} + +DEFINE_SUITE("Ftrace return address processing", ftrace); diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h index 9c96f33483d1..1aec32e094c8 100644 --- a/tools/perf/tests/tests.h +++ b/tools/perf/tests/tests.h @@ -163,6 +163,7 @@ DECLARE_SUITE(perf_hooks); DECLARE_SUITE(unit_number__scnprint); DECLARE_SUITE(mem2node); DECLARE_SUITE(maps); +DECLARE_SUITE(ftrace); DECLARE_SUITE(time_utils); DECLARE_SUITE(jit_write_elf); DECLARE_SUITE(api_io); diff --git a/tools/perf/util/Build b/tools/perf/util/Build index 2c1f880c4c47..5b082d09006d 100644 --- a/tools/perf/util/Build +++ b/tools/perf/util/Build @@ -169,6 +169,7 @@ perf-util-y += list_sort.o perf-util-y += mutex.o perf-util-y += sharded_mutex.o perf-util-y += intel-tpebs.o +perf-util-y += ftrace.o perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf_counter.o perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf_counter_cgroup.o diff --git a/tools/perf/util/ftrace.c b/tools/perf/util/ftrace.c new file mode 100644 index 000000000000..344d36293f5c --- /dev/null +++ b/tools/perf/util/ftrace.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include "util/ftrace.h" + +/** + * ftrace_parse_retaddr - Parse return address comment from trace line + * @str: The trace line containing the comment + * @sym_name: Buffer to store the parsed symbol name + * @sym_len: Length of the @sym_name buffer + * @offset: Pointer to store the parsed offset + * + * Extract the function name and offset from a funcgraph-retaddr comment + * (e.g. "<-load_elf_phdrs+0x6c/0xb0"). + * + * Return: true if successfully parsed, false otherwise. + */ +bool ftrace_parse_retaddr(const char *str, char *sym_name, size_t sym_len, u64 *offset) +{ + const char *p = strstr(str, "<-"); + const char *plus; + const char *bracket; + char *endptr; + size_t name_len; + + if (!p) + return false; + + p += 2; + while (*p == ' ') + p++; + + if (*p == '[') { + bracket = strchr(p, ']'); + if (bracket) + p = bracket + 1; + while (*p == ' ') + p++; + } + + plus = strchr(p, '+'); + if (!plus) + return false; + + name_len = plus - p; + if (name_len == 0 || name_len >= sym_len) + return false; + + memcpy(sym_name, p, name_len); + sym_name[name_len] = '\0'; + + *offset = strtoull(plus + 1, &endptr, 16); + return true; +} + +/** + * ftrace_filter_retaddr - Remove return address comment from trace line + * @str: The trace line to modify + * + * Find and strip the funcgraph-retaddr comment from the trace line + * in-place, removing trailing spaces where applicable. + */ +void ftrace_filter_retaddr(char *str) +{ + char *start = strstr(str, "/* <-"); + char *end; + + if (!start) + return; + + end = strstr(start, "*/"); + if (!end) + return; + + end += 2; /* skip end-of-comment delimiter */ + + /* Also backtrack any spaces before comment */ + while (start > str && *(start - 1) == ' ') + start--; + + memmove(start, end, strlen(end) + 1); +} diff --git a/tools/perf/util/ftrace.h b/tools/perf/util/ftrace.h index 950f2efafad2..50216d3fef64 100644 --- a/tools/perf/util/ftrace.h +++ b/tools/perf/util/ftrace.h @@ -39,6 +39,8 @@ struct perf_ftrace { int graph_verbose; int graph_thresh; int graph_tail; + bool filter_retaddr; + bool filter_retaddr_set; }; struct filter_entry { @@ -93,4 +95,7 @@ perf_ftrace__latency_cleanup_bpf(struct perf_ftrace *ftrace __maybe_unused) #endif /* HAVE_BPF_SKEL */ +bool ftrace_parse_retaddr(const char *str, char *sym_name, size_t sym_len, u64 *offset); +void ftrace_filter_retaddr(char *str); + #endif /* __PERF_FTRACE_H__ */ -- 2.55.0