[PATCH] perf tools: Add OCaml demangling

* [PATCH] perf tools: Add OCaml demangling
@ 2021-02-03 21:15 Fabian Hemmer
  2021-02-16  7:47 ` Namhyung Kim
  0 siblings, 1 reply; 3+ messages in thread
From: Fabian Hemmer @ 2021-02-03 21:15 UTC (permalink / raw)
  To: linux-perf-users
  Cc: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
	Mark Rutland, Alexander Shishkin, Jiri Olsa, Namhyung Kim

Detect symbols generated by the OCaml compiler based on their prefix.

Demangle OCaml symbols, returning a newly allocated string (like the
existing Java demangling functionality).

Move a helper function (hex) from tests/code-reading.c to util/string.c

To test:

echo 'Printf.printf "%d\n" (Random.int 42)' > test.ml
perf record ocamlopt.opt test.ml
perf report -d ocamlopt.opt

Signed-off-by: Fabian Hemmer <copy@copy.sh>
---
 tools/perf/tests/Build                 |  1 +
 tools/perf/tests/builtin-test.c        |  4 ++
 tools/perf/tests/code-reading.c        | 10 +---
 tools/perf/tests/demangle-ocaml-test.c | 43 ++++++++++++++
 tools/perf/tests/tests.h               |  1 +
 tools/perf/util/Build                  |  1 +
 tools/perf/util/demangle-ocaml.c       | 80 ++++++++++++++++++++++++++
 tools/perf/util/demangle-ocaml.h       |  7 +++
 tools/perf/util/string.c               |  9 +++
 tools/perf/util/string2.h              |  2 +
 tools/perf/util/symbol-elf.c           |  9 ++-
 11 files changed, 156 insertions(+), 11 deletions(-)
 create mode 100644 tools/perf/tests/demangle-ocaml-test.c
 create mode 100644 tools/perf/util/demangle-ocaml.c
 create mode 100644 tools/perf/util/demangle-ocaml.h

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index aa4dc4f5abde..650aec19d490 100644
--- a/tools/perf/tests/Build
+++ b/tools/perf/tests/Build
@@ -58,6 +58,7 @@ perf-y += time-utils-test.o
 perf-y += genelf.o
 perf-y += api-io.o
 perf-y += demangle-java-test.o
+perf-y += demangle-ocaml-test.o
 perf-y += pfm.o
 perf-y += parse-metric.o
 perf-y += pe-file-parsing.o
diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 7273823d0d02..c4b888f18e9c 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -338,6 +338,10 @@ static struct test generic_tests[] = {
 		.desc = "Demangle Java",
 		.func = test__demangle_java,
 	},
+	{
+		.desc = "Demangle OCaml",
+		.func = test__demangle_ocaml,
+	},
 	{
 		.desc = "Parse and process metrics",
 		.func = test__parse_metric,
diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index 7c098d49c77e..280f0348a09c 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -26,6 +26,7 @@
 #include "event.h"
 #include "record.h"
 #include "util/mmap.h"
+#include "util/string2.h"
 #include "util/synthetic-events.h"
 #include "thread.h"
 
@@ -41,15 +42,6 @@ struct state {
 	size_t done_cnt;
 };
 
-static unsigned int hex(char c)
-{
-	if (c >= '0' && c <= '9')
-		return c - '0';
-	if (c >= 'a' && c <= 'f')
-		return c - 'a' + 10;
-	return c - 'A' + 10;
-}
-
 static size_t read_objdump_chunk(const char **line, unsigned char **buf,
 				 size_t *buf_len)
 {
diff --git a/tools/perf/tests/demangle-ocaml-test.c b/tools/perf/tests/demangle-ocaml-test.c
new file mode 100644
index 000000000000..a273ed5163d7
--- /dev/null
+++ b/tools/perf/tests/demangle-ocaml-test.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "tests.h"
+#include "session.h"
+#include "debug.h"
+#include "demangle-ocaml.h"
+
+int test__demangle_ocaml(struct test *test __maybe_unused, int subtest __maybe_unused)
+{
+	int ret = TEST_OK;
+	char *buf = NULL;
+	size_t i;
+
+	struct {
+		const char *mangled, *demangled;
+	} test_cases[] = {
+		{ "main",
+		  NULL },
+		{ "camlStdlib__array__map_154",
+		  "Stdlib.array.map" },
+		{ "camlStdlib__anon_fn$5bstdlib$2eml$3a334$2c0$2d$2d54$5d_1453",
+		  "Stdlib.anon_fn[stdlib.ml:334,0--54]" },
+		{ "camlStdlib__bytes__$2b$2b_2205",
+		  "Stdlib.bytes.++" },
+	};
+
+	for (i = 0; i < sizeof(test_cases) / sizeof(test_cases[0]); i++) {
+		buf = ocaml_demangle_sym(test_cases[i].mangled);
+		if ((buf == NULL && test_cases[i].demangled != NULL)
+				|| (buf != NULL && test_cases[i].demangled == NULL)
+				|| (buf != NULL && strcmp(buf, test_cases[i].demangled))) {
+			pr_debug("FAILED: %s: %s != %s\n", test_cases[i].mangled,
+				 buf == NULL ? "(null)" : buf,
+				 test_cases[i].demangled == NULL ? "(null)" : test_cases[i].demangled);
+			ret = TEST_FAIL;
+		}
+		free(buf);
+	}
+
+	return ret;
+}
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 8e24a61fe4c2..b85f005308a3 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -119,6 +119,7 @@ int test__time_utils(struct test *t, int subtest);
 int test__jit_write_elf(struct test *test, int subtest);
 int test__api_io(struct test *test, int subtest);
 int test__demangle_java(struct test *test, int subtest);
+int test__demangle_ocaml(struct test *test, int subtest);
 int test__pfm(struct test *test, int subtest);
 const char *test__pfm_subtest_get_desc(int subtest);
 int test__pfm_subtest_get_nr(void);
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index e2563d0154eb..34995e1fef8f 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -172,6 +172,7 @@ perf-$(CONFIG_ZSTD) += zstd.o
 
 perf-$(CONFIG_LIBCAP) += cap.o
 
+perf-y += demangle-ocaml.o
 perf-y += demangle-java.o
 perf-y += demangle-rust.o
 
diff --git a/tools/perf/util/demangle-ocaml.c b/tools/perf/util/demangle-ocaml.c
new file mode 100644
index 000000000000..3df14e67c622
--- /dev/null
+++ b/tools/perf/util/demangle-ocaml.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <string.h>
+#include <stdlib.h>
+#include "util/string2.h"
+
+#include "demangle-ocaml.h"
+
+#include <linux/ctype.h>
+
+static const char *caml_prefix = "caml";
+static const size_t caml_prefix_len = 4;
+
+/* mangled OCaml symbols start with "caml" followed by an upper-case letter */
+static bool
+ocaml_is_mangled(const char *sym)
+{
+	return 0 == strncmp(sym, caml_prefix, caml_prefix_len)
+		&& isupper(sym[caml_prefix_len]);
+}
+
+/*
+ * input:
+ *     sym: a symbol which may have been mangled by the OCaml compiler
+ * return:
+ *     if the input doesn't look like a mangled OCaml symbol, NULL is returned
+ *     otherwise, a newly allocated string containing the demangled symbol is returned
+ */
+char *
+ocaml_demangle_sym(const char *sym)
+{
+	char *result;
+	int j = 0;
+	int i;
+	int len;
+
+	if (!ocaml_is_mangled(sym)) {
+		return NULL;
+	}
+
+	len = strlen(sym);
+
+	/* the demangled symbol is always smaller than the mangled symbol */
+	result = malloc(len + 1);
+	if (!result)
+		return NULL;
+
+	/* skip "caml" prefix */
+	i = caml_prefix_len;
+
+	while (i < len) {
+		if (sym[i] == '_' && sym[i + 1] == '_') {
+			/* "__" -> "." */
+			result[j++] = '.';
+			i += 2;
+		}
+		else if (sym[i] == '$' && isxdigit(sym[i + 1]) && isxdigit(sym[i + 2])) {
+			/* "$xx" is a hex-encoded character */
+			result[j++] = (hex(sym[i + 1]) << 4) | hex(sym[i + 2]);
+			i += 3;
+		}
+		else {
+			result[j++] = sym[i++];
+		}
+	}
+	result[j] = '\0';
+
+	/* scan backwards to remove an "_" followed by decimal digits */
+	if (j != 0 && isdigit(result[j - 1])) {
+		while (--j) {
+			if (!isdigit(result[j])) {
+				break;
+			}
+		}
+		if (result[j] == '_') {
+			result[j] = '\0';
+		}
+	}
+
+	return result;
+}
diff --git a/tools/perf/util/demangle-ocaml.h b/tools/perf/util/demangle-ocaml.h
new file mode 100644
index 000000000000..843cc4fa10a6
--- /dev/null
+++ b/tools/perf/util/demangle-ocaml.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_DEMANGLE_OCAML
+#define __PERF_DEMANGLE_OCAML 1
+
+char * ocaml_demangle_sym(const char *str);
+
+#endif /* __PERF_DEMANGLE_OCAML */
diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
index 52603876c548..f6d90cdd9225 100644
--- a/tools/perf/util/string.c
+++ b/tools/perf/util/string.c
@@ -293,3 +293,12 @@ char *strdup_esc(const char *str)
 
 	return ret;
 }
+
+unsigned int hex(char c)
+{
+	if (c >= '0' && c <= '9')
+		return c - '0';
+	if (c >= 'a' && c <= 'f')
+		return c - 'a' + 10;
+	return c - 'A' + 10;
+}
diff --git a/tools/perf/util/string2.h b/tools/perf/util/string2.h
index 73df616ced43..56c30fef9682 100644
--- a/tools/perf/util/string2.h
+++ b/tools/perf/util/string2.h
@@ -38,4 +38,6 @@ char *asprintf__tp_filter_pids(size_t npids, pid_t *pids);
 char *strpbrk_esc(char *str, const char *stopset);
 char *strdup_esc(const char *str);
 
+unsigned int hex(char c);
+
 #endif /* PERF_STRING_H */
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index f3577f7d72fe..1e9114592f2e 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -12,6 +12,7 @@
 #include "maps.h"
 #include "symbol.h"
 #include "symsrc.h"
+#include "demangle-ocaml.h"
 #include "demangle-java.h"
 #include "demangle-rust.h"
 #include "machine.h"
@@ -251,8 +252,12 @@ static char *demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
 	    return demangled;
 
 	demangled = bfd_demangle(NULL, elf_name, demangle_flags);
-	if (demangled == NULL)
-		demangled = java_demangle_sym(elf_name, JAVA_DEMANGLE_NORET);
+	if (demangled == NULL) {
+		demangled = ocaml_demangle_sym(elf_name);
+		if (demangled == NULL) {
+			demangled = java_demangle_sym(elf_name, JAVA_DEMANGLE_NORET);
+		}
+	}
 	else if (rust_is_mangled(demangled))
 		/*
 		    * Input to Rust demangling is the BFD-demangled
-- 
2.30.0


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