perf dlfilter: Add al_cleanup()

Add perf_dlfilter_fns.al_cleanup() to do addr_location__exit() on data
passed via perf_dlfilter_fns.resolve_address().

Add dlfilter-test-api-v2 to the "dlfilter C API" test to test it.

Update documentation, clarifying that data returned by APIs should not
be dereferenced after filter_event() and filter_event_early() return.

Fixes: 0dd5041c ("perf addr_location: Add init/exit/copy functions")
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20230731091857.10681-3-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-dlfilter.txt

@@ -64,6 +64,12 @@ internal filtering.
 If implemented, 'filter_description' should return a one-line description
 of the filter, and optionally a longer description.
 
+Do not assume the 'sample' argument is valid (dereferenceable)
+after 'filter_event' and 'filter_event_early' return.
+
+Do not assume data referenced by pointers in struct perf_dlfilter_sample
+is valid (dereferenceable) after 'filter_event' and 'filter_event_early' return.
+
 The perf_dlfilter_sample structure
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -150,7 +156,8 @@ struct perf_dlfilter_fns {
 	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 *);
+	void (*al_cleanup)(void *ctx, struct perf_dlfilter_al *al);
+	void *(*reserved[119])(void *);
 };
 ----
 
@@ -161,7 +168,8 @@ struct perf_dlfilter_fns {
 '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.
+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.
 
@@ -171,6 +179,12 @@ before calling. Returns 0 on success, -1 otherwise.
 
 '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
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -197,9 +211,13 @@ struct perf_dlfilter_al {
 	/* 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.
+
 perf_dlfilter_sample flags
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tools/perf/Makefile.perf

@@ -377,7 +377,7 @@ ifndef NO_JVMTI
 PROGRAMS += $(OUTPUT)$(LIBJVMTI)
 endif
 
-DLFILTERS := dlfilter-test-api-v0.so dlfilter-show-cycles.so
+DLFILTERS := dlfilter-test-api-v0.so dlfilter-test-api-v2.so dlfilter-show-cycles.so
 DLFILTERS := $(patsubst %,$(OUTPUT)dlfilters/%,$(DLFILTERS))
 
 # what 'all' will build and 'install' will install, in perfexecdir

tools/perf/include/perf/perf_dlfilter.h

@@ -91,6 +91,7 @@ struct perf_dlfilter_al {
 	/* 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 */
 };
 
 struct perf_dlfilter_fns {
@@ -102,7 +103,8 @@ struct perf_dlfilter_fns {
 	char **(*args)(void *ctx, int *dlargc);
 	/*
 	 * Return information about address (al->size must be set before
-	 * calling). Returns 0 on success, -1 otherwise.
+	 * calling). Returns 0 on success, -1 otherwise. Call al_cleanup()
+	 * when 'al' data is no longer needed.
 	 */
 	__s32 (*resolve_address)(void *ctx, __u64 address, struct perf_dlfilter_al *al);
 	/* Return instruction bytes and length */
@@ -113,8 +115,13 @@ struct perf_dlfilter_fns {
 	struct perf_event_attr *(*attr)(void *ctx);
 	/* Read object code, return numbers of bytes read */
 	__s32 (*object_code)(void *ctx, __u64 ip, void *buf, __u32 len);
+	/*
+	 * If present (i.e. must check al_cleanup != NULL), call after
+	 * resolve_address() to free any associated resources.
+	 */
+	void (*al_cleanup)(void *ctx, struct perf_dlfilter_al *al);
 	/* Reserved */
-	void *(*reserved[120])(void *);
+	void *(*reserved[119])(void *);
 };
 
 /*

tools/perf/tests/dlfilter-test.c

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Test dlfilter C API. A perf.data file is synthesized and then processed
- * by perf script with a dlfilter named dlfilter-test-api-v0.so. Also a C file
+ * by perf script with dlfilters named dlfilter-test-api-v*.so. Also a C file
  * is compiled to provide a dso to match the synthesized perf.data file.
  */
 
@@ -37,6 +37,8 @@
 
 #define MAP_START 0x400000
 
+#define DLFILTER_TEST_NAME_MAX 128
+
 struct test_data {
 	struct perf_tool tool;
 	struct machine *machine;
@@ -45,6 +47,8 @@ struct test_data {
 	u64 bar;
 	u64 ip;
 	u64 addr;
+	char name[DLFILTER_TEST_NAME_MAX];
+	char desc[DLFILTER_TEST_NAME_MAX];
 	char perf[PATH_MAX];
 	char perf_data_file_name[PATH_MAX];
 	char c_file_name[PATH_MAX];
@@ -215,7 +219,7 @@ static int write_prog(char *file_name)
 	return err ? -1 : 0;
 }
 
-static int get_dlfilters_path(char *buf, size_t sz)
+static int get_dlfilters_path(const char *name, char *buf, size_t sz)
 {
 	char perf[PATH_MAX];
 	char path[PATH_MAX];
@@ -224,12 +228,12 @@ static int get_dlfilters_path(char *buf, size_t sz)
 
 	perf_exe(perf, sizeof(perf));
 	perf_path = dirname(perf);
-	snprintf(path, sizeof(path), "%s/dlfilters/dlfilter-test-api-v0.so", perf_path);
+	snprintf(path, sizeof(path), "%s/dlfilters/%s", perf_path, name);
 	if (access(path, R_OK)) {
 		exec_path = get_argv_exec_path();
 		if (!exec_path)
 			return -1;
-		snprintf(path, sizeof(path), "%s/dlfilters/dlfilter-test-api-v0.so", exec_path);
+		snprintf(path, sizeof(path), "%s/dlfilters/%s", exec_path, name);
 		free(exec_path);
 		if (access(path, R_OK))
 			return -1;
@@ -244,9 +248,9 @@ static int check_filter_desc(struct test_data *td)
 	char *desc = NULL;
 	int ret;
 
-	if (get_filter_desc(td->dlfilters, "dlfilter-test-api-v0.so", &desc, &long_desc) &&
+	if (get_filter_desc(td->dlfilters, td->name, &desc, &long_desc) &&
 	    long_desc && !strcmp(long_desc, "Filter used by the 'dlfilter C API' perf test") &&
-	    desc && !strcmp(desc, "dlfilter to test v0 C API"))
+	    desc && !strcmp(desc, td->desc))
 		ret = 0;
 	else
 		ret = -1;
@@ -284,7 +288,7 @@ static int get_ip_addr(struct test_data *td)
 static int do_run_perf_script(struct test_data *td, int do_early)
 {
 	return system_cmd("%s script -i %s "
-			  "--dlfilter %s/dlfilter-test-api-v0.so "
+			  "--dlfilter %s/%s "
 			  "--dlarg first "
 			  "--dlarg %d "
 			  "--dlarg %" PRIu64 " "
@@ -292,7 +296,7 @@ static int do_run_perf_script(struct test_data *td, int do_early)
 			  "--dlarg %d "
 			  "--dlarg last",
 			  td->perf, td->perf_data_file_name, td->dlfilters,
-			  verbose, td->ip, td->addr, do_early);
+			  td->name, verbose, td->ip, td->addr, do_early);
 }
 
 static int run_perf_script(struct test_data *td)
@@ -321,7 +325,7 @@ static int test__dlfilter_test(struct test_data *td)
 	u64 id = 99;
 	int err;
 
-	if (get_dlfilters_path(td->dlfilters, PATH_MAX))
+	if (get_dlfilters_path(td->name, td->dlfilters, PATH_MAX))
 		return test_result("dlfilters not found", TEST_SKIP);
 
 	if (check_filter_desc(td))
@@ -399,14 +403,18 @@ static void test_data__free(struct test_data *td)
 	}
 }
 
-static int test__dlfilter(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+static int test__dlfilter_ver(int ver)
 {
 	struct test_data td = {.fd = -1};
 	int pid = getpid();
 	int err;
 
+	pr_debug("\n-- Testing version %d API --\n", ver);
+
 	perf_exe(td.perf, sizeof(td.perf));
 
+	snprintf(td.name, sizeof(td.name), "dlfilter-test-api-v%d.so", ver);
+	snprintf(td.desc, sizeof(td.desc), "dlfilter to test v%d C API", ver);
 	snprintf(td.perf_data_file_name, PATH_MAX, "/tmp/dlfilter-test-%u-perf-data", pid);
 	snprintf(td.c_file_name, PATH_MAX, "/tmp/dlfilter-test-%u-prog.c", pid);
 	snprintf(td.prog_file_name, PATH_MAX, "/tmp/dlfilter-test-%u-prog", pid);
@@ -416,4 +424,14 @@ static int test__dlfilter(struct test_suite *test __maybe_unused, int subtest __
 	return err;
 }
 
+static int test__dlfilter(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	int err = test__dlfilter_ver(0);
+
+	if (err)
+		return err;
+	/* No test for version 1 */
+	return test__dlfilter_ver(2);
+}
+
 DEFINE_SUITE("dlfilter C API", dlfilter);

tools/perf/util/dlfilter.c

@@ -10,6 +10,8 @@
 #include <subcmd/exec-cmd.h>
 #include <linux/zalloc.h>
 #include <linux/build_bug.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
 
 #include "debug.h"
 #include "event.h"
@@ -63,6 +65,7 @@ static void al_to_d_al(struct addr_location *al, struct perf_dlfilter_al *d_al)
 	d_al->addr = al->addr;
 	d_al->comm = NULL;
 	d_al->filtered = 0;
+	d_al->priv = NULL;
 }
 
 static struct addr_location *get_al(struct dlfilter *d)
@@ -151,6 +154,11 @@ static char **dlfilter__args(void *ctx, int *dlargc)
 	return d->dlargv;
 }
 
+static bool has_priv(struct perf_dlfilter_al *d_al_p)
+{
+	return d_al_p->size >= offsetof(struct perf_dlfilter_al, priv) + sizeof(d_al_p->priv);
+}
+
 static __s32 dlfilter__resolve_address(void *ctx, __u64 address, struct perf_dlfilter_al *d_al_p)
 {
 	struct dlfilter *d = (struct dlfilter *)ctx;
@@ -177,9 +185,29 @@ static __s32 dlfilter__resolve_address(void *ctx, __u64 address, struct perf_dlf
 	memcpy(d_al_p, &d_al, min((size_t)sz, sizeof(d_al)));
 	d_al_p->size = sz;
 
+	if (has_priv(d_al_p))
+		d_al_p->priv = memdup(&al, sizeof(al));
+
 	return 0;
 }
 
+static void dlfilter__al_cleanup(void *ctx __maybe_unused, struct perf_dlfilter_al *d_al_p)
+{
+	struct addr_location *al;
+
+	/* Ensure backward compatibility */
+	if (!has_priv(d_al_p) || !d_al_p->priv)
+		return;
+
+	al = d_al_p->priv;
+
+	d_al_p->priv = NULL;
+
+	addr_location__exit(al);
+
+	free(al);
+}
+
 static const __u8 *dlfilter__insn(void *ctx, __u32 *len)
 {
 	struct dlfilter *d = (struct dlfilter *)ctx;
@@ -297,6 +325,7 @@ static const struct perf_dlfilter_fns perf_dlfilter_fns = {
 	.resolve_addr    = dlfilter__resolve_addr,
 	.args            = dlfilter__args,
 	.resolve_address = dlfilter__resolve_address,
+	.al_cleanup      = dlfilter__al_cleanup,
 	.insn            = dlfilter__insn,
 	.srcline         = dlfilter__srcline,
 	.attr            = dlfilter__attr,