diff mbox series

[bpf-next,v10,1/2] selftests/bpf: trace_helpers.c: optimize kallsyms cache

Message ID tencent_0A73B402B1D440480838ABF7124CE5EA5505@qq.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series selftests/bpf: Optimize kallsyms cache | expand

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netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 9 this patch: 9
netdev/cc_maintainers success CCed 21 of 21 maintainers
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netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 9 this patch: 9
netdev/checkpatch warning CHECK: Alignment should match open parenthesis CHECK: No space is necessary after a cast CHECK: Please use a blank line after function/struct/union/enum declarations WARNING: line length of 81 exceeds 80 columns
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Commit Message

Rong Tao Sept. 4, 2023, 1:01 a.m. UTC 
From: Rong Tao <rongtao@cestc.cn>

Static ksyms often have problems because the number of symbols exceeds the
MAX_SYMS limit. Like changing the MAX_SYMS from 300000 to 400000 in
commit e76a014334a6("selftests/bpf: Bump and validate MAX_SYMS") solves
the problem somewhat, but it's not the perfect way.

This commit uses dynamic memory allocation, which completely solves the
problem caused by the limitation of the number of kallsyms. At the same
time, add APIs:

    load_kallsyms_local()
    ksym_search_local()
    ksym_get_addr_local()

There are used to solve the problem of selftests/bpf updating kallsyms
after attach new symbols during testmod testing.

Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Rong Tao <rongtao@cestc.cn>
---
v10: Keep the original load_kallsyms().
v9: https://lore.kernel.org/lkml/tencent_254B7015EED7A5D112C45E033DA1822CF107@qq.com/
    Add load_kallsyms_local,ksym_search_local,ksym_get_addr_local functions.
v8: https://lore.kernel.org/lkml/tencent_6D23FE187408D965E95DFAA858BC7E8C760A@qq.com/
    Resolves inter-thread contention for ksyms global variables.
v7: https://lore.kernel.org/lkml/tencent_BD6E19C00BF565CD5C36A9A0BD828CFA210A@qq.com/
    Fix __must_check macro.
v6: https://lore.kernel.org/lkml/tencent_4A09A36F883A06EA428A593497642AF8AF08@qq.com/
    Apply libbpf_ensure_mem()
v5: https://lore.kernel.org/lkml/tencent_0E9E1A1C0981678D5E7EA9E4BDBA8EE2200A@qq.com/
    Release the allocated memory once the load_kallsyms_refresh() upon error
    given it's dynamically allocated.
v4: https://lore.kernel.org/lkml/tencent_59C74613113F0C728524B2A82FE5540A5E09@qq.com/
    Make sure most cases we don't need the realloc() path to begin with,
    and check strdup() return value.
v3: https://lore.kernel.org/lkml/tencent_50B4B2622FE7546A5FF9464310650C008509@qq.com/
    Do not use structs and judge ksyms__add_symbol function return value.
v2: https://lore.kernel.org/lkml/tencent_B655EE5E5D463110D70CD2846AB3262EED09@qq.com/
    Do the usual len/capacity scheme here to amortize the cost of realloc, and
    don't free symbols.
v1: https://lore.kernel.org/lkml/tencent_AB461510B10CD484E0B2F62E3754165F2909@qq.com/
---
 samples/bpf/Makefile                          |   4 +
 .../selftests/bpf/prog_tests/fill_link_info.c |   9 +-
 .../prog_tests/kprobe_multi_testmod_test.c    |  24 ++-
 tools/testing/selftests/bpf/trace_helpers.c   | 137 +++++++++++++-----
 tools/testing/selftests/bpf/trace_helpers.h   |  10 +-
 5 files changed, 137 insertions(+), 47 deletions(-)

Comments

Jiri Olsa Sept. 4, 2023, 7:51 p.m. UTC | #1 
On Mon, Sep 04, 2023 at 09:01:20AM +0800, Rong Tao wrote:
> From: Rong Tao <rongtao@cestc.cn>
> 
> Static ksyms often have problems because the number of symbols exceeds the
> MAX_SYMS limit. Like changing the MAX_SYMS from 300000 to 400000 in
> commit e76a014334a6("selftests/bpf: Bump and validate MAX_SYMS") solves
> the problem somewhat, but it's not the perfect way.
> 
> This commit uses dynamic memory allocation, which completely solves the
> problem caused by the limitation of the number of kallsyms. At the same
> time, add APIs:
> 
>     load_kallsyms_local()
>     ksym_search_local()
>     ksym_get_addr_local()

missing free_kallsyms_local

> diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> index 9d768e083714..13e618317c8b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> +++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> @@ -302,16 +302,18 @@ void test_fill_link_info(void)
>  {
>  	struct test_fill_link_info *skel;
>  	int i;
> +	struct ksyms *ksyms;
>  
>  	skel = test_fill_link_info__open_and_load();
>  	if (!ASSERT_OK_PTR(skel, "skel_open"))
>  		return;
>  
>  	/* load kallsyms to compare the addr */
> -	if (!ASSERT_OK(load_kallsyms_refresh(), "load_kallsyms_refresh"))
> +	ksyms = load_kallsyms_local();
> +	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_local"))
>  		goto cleanup;

actually I don't see why this test should need refreshed kallsyms,
it doesn't load/unload testmod, I think it can use global ksyms

>  
> -	kprobe_addr = ksym_get_addr(KPROBE_FUNC);
> +	kprobe_addr = ksym_get_addr_local(ksyms, KPROBE_FUNC);
>  	if (test__start_subtest("kprobe_link_info"))
>  		test_kprobe_fill_link_info(skel, BPF_PERF_EVENT_KPROBE, false);
>  	if (test__start_subtest("kretprobe_link_info"))
> @@ -329,7 +331,7 @@ void test_fill_link_info(void)
>  
>  	qsort(kmulti_syms, KMULTI_CNT, sizeof(kmulti_syms[0]), symbols_cmp_r);
>  	for (i = 0; i < KMULTI_CNT; i++)
> -		kmulti_addrs[i] = ksym_get_addr(kmulti_syms[i]);
> +		kmulti_addrs[i] = ksym_get_addr_local(ksyms, kmulti_syms[i]);
>  	if (test__start_subtest("kprobe_multi_link_info"))
>  		test_kprobe_multi_fill_link_info(skel, false, false);
>  	if (test__start_subtest("kretprobe_multi_link_info"))
> @@ -339,4 +341,5 @@ void test_fill_link_info(void)
>  
>  cleanup:
>  	test_fill_link_info__destroy(skel);
> +	free_kallsyms_local(ksyms);
>  }
> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c
> index 1fbe7e4ac00a..532b05ae2da4 100644
> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c
> @@ -4,6 +4,8 @@
>  #include "trace_helpers.h"
>  #include "bpf/libbpf_internal.h"
>  
> +static struct ksyms *ksyms;
> +
>  static void kprobe_multi_testmod_check(struct kprobe_multi *skel)
>  {
>  	ASSERT_EQ(skel->bss->kprobe_testmod_test1_result, 1, "kprobe_test1_result");
> @@ -50,12 +52,12 @@ static void test_testmod_attach_api_addrs(void)
>  	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
>  	unsigned long long addrs[3];
>  
> -	addrs[0] = ksym_get_addr("bpf_testmod_fentry_test1");
> -	ASSERT_NEQ(addrs[0], 0, "ksym_get_addr");
> -	addrs[1] = ksym_get_addr("bpf_testmod_fentry_test2");
> -	ASSERT_NEQ(addrs[1], 0, "ksym_get_addr");
> -	addrs[2] = ksym_get_addr("bpf_testmod_fentry_test3");
> -	ASSERT_NEQ(addrs[2], 0, "ksym_get_addr");
> +	addrs[0] = ksym_get_addr_local(ksyms, "bpf_testmod_fentry_test1");
> +	ASSERT_NEQ(addrs[0], 0, "ksym_get_addr_local");
> +	addrs[1] = ksym_get_addr_local(ksyms, "bpf_testmod_fentry_test2");
> +	ASSERT_NEQ(addrs[1], 0, "ksym_get_addr_local");
> +	addrs[2] = ksym_get_addr_local(ksyms, "bpf_testmod_fentry_test3");
> +	ASSERT_NEQ(addrs[2], 0, "ksym_get_addr_local");
>  
>  	opts.addrs = (const unsigned long *) addrs;
>  	opts.cnt = ARRAY_SIZE(addrs);
> @@ -79,11 +81,19 @@ static void test_testmod_attach_api_syms(void)
>  
>  void serial_test_kprobe_multi_testmod_test(void)
>  {
> -	if (!ASSERT_OK(load_kallsyms_refresh(), "load_kallsyms_refresh"))
> +	ksyms = load_kallsyms_local();
> +	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_local"))
>  		return;
>  
>  	if (test__start_subtest("testmod_attach_api_syms"))
>  		test_testmod_attach_api_syms();
> +
> +	ksyms = load_kallsyms_refresh(ksyms);
> +	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_refresh"))
> +		return;

hm, this refresh is not needed right? the test got the fresh kallsyms above
and both test_testmod_attach_api_syms and test_testmod_attach_api_addrs
should be happy

> +
>  	if (test__start_subtest("testmod_attach_api_addrs"))
>  		test_testmod_attach_api_addrs();
> +
> +	free_kallsyms_local(ksyms);
>  }
> diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
> index f83d9f65c65b..d64c4ef336e1 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.c
> +++ b/tools/testing/selftests/bpf/trace_helpers.c
> @@ -14,104 +14,171 @@
>  #include <linux/limits.h>
>  #include <libelf.h>
>  #include <gelf.h>
> +#include "bpf/libbpf_internal.h"
>  
>  #define TRACEFS_PIPE	"/sys/kernel/tracing/trace_pipe"
>  #define DEBUGFS_PIPE	"/sys/kernel/debug/tracing/trace_pipe"
>  
> -#define MAX_SYMS 400000
> -static struct ksym syms[MAX_SYMS];
> -static int sym_cnt;
> +struct ksyms {
> +	struct ksym *syms;
> +	size_t sym_cap;
> +	size_t sym_cnt;
> +};
> +
> +static struct ksyms *ksyms;
> +
> +static int ksyms__add_symbol(struct ksyms *ksyms, const char *name,
> +							 unsigned long addr)

extra white space in here ^^^

> +{
> +	void *tmp;
> +
> +	tmp = strdup(name);
> +	if (!tmp)
> +		return -ENOMEM;
> +	ksyms->syms[ksyms->sym_cnt].addr = addr;
> +	ksyms->syms[ksyms->sym_cnt].name = tmp;
> +
> +	ksyms->sym_cnt++;
> +
> +	return 0;
> +}
> +
> +void free_kallsyms_local(struct ksyms *ksyms)
> +{
> +	unsigned int i;
> +
> +	if (!ksyms)
> +		return;
> +
> +	if (!ksyms->syms) {
> +		free(ksyms);
> +		return;
> +	}
> +
> +	for (i = 0; i < ksyms->sym_cnt; i++)
> +		free(ksyms->syms[i].name);
> +	free(ksyms->syms);
> +	free(ksyms);
> +}
>  
>  static int ksym_cmp(const void *p1, const void *p2)
>  {
>  	return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
>  }
>  
> -int load_kallsyms_refresh(void)
> +struct ksyms *load_kallsyms_refresh(struct ksyms *ksyms)
>  {
>  	FILE *f;
>  	char func[256], buf[256];
>  	char symbol;
>  	void *addr;
> -	int i = 0;
> +	int ret;
>  
> -	sym_cnt = 0;
> +	/* flush kallsyms, free the previously allocated dynamic memory */
> +	free_kallsyms_local(ksyms);
>  
>  	f = fopen("/proc/kallsyms", "r");
>  	if (!f)
> -		return -ENOENT;
> +		return NULL;
> +
> +	ksyms = calloc(1, sizeof(struct ksyms));
> +	if (!ksyms)
> +		return NULL;

I wonder it could be easier not to allocate ksyms, but just let the
caller to pass the pointer to 'ksym' variable on stack.. but there
might be other problems, so I guess this is fine

>  
>  	while (fgets(buf, sizeof(buf), f)) {
>  		if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
>  			break;
>  		if (!addr)
>  			continue;
> -		if (i >= MAX_SYMS)
> -			return -EFBIG;
>  
> -		syms[i].addr = (long) addr;
> -		syms[i].name = strdup(func);
> -		i++;
> +		ret = libbpf_ensure_mem((void **) &ksyms->syms, &ksyms->sym_cap,
> +					sizeof(struct ksym), ksyms->sym_cnt + 1);
> +		if (ret)
> +			goto error;
> +		ret = ksyms__add_symbol(ksyms, func, (unsigned long)addr);
> +		if (ret)
> +			goto error;
>  	}
>  	fclose(f);
> -	sym_cnt = i;
> -	qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
> -	return 0;
> +	qsort(ksyms->syms, ksyms->sym_cnt, sizeof(struct ksym), ksym_cmp);
> +	return ksyms;
> +
> +error:
> +	free_kallsyms_local(ksyms);
> +	return NULL;
> +}
> +
> +struct ksyms *load_kallsyms_local(void)
> +{
> +	return load_kallsyms_refresh(NULL);

I think we can have just:

   struct ksyms *load_kallsyms_local(struct ksyms *ksyms);

I don't see reason for load_kallsyms_refresh functions, perhaps it's
leftover because I don't see the function in the changelog

thanks,
jirka
Rong Tao Sept. 5, 2023, 2:21 p.m. UTC | #2 
Hi, jirka.

I just fix all your advise[0], and submit new patchset v11.
please review.

Rong Tao

[0] https://lore.kernel.org/lkml/ZPY1Lu8341L+d5Rw@krava/
diff mbox series

Patch

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4ccf4236031c..6c707ebcebb9 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -175,6 +175,7 @@  TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
 TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
 TPROGS_CFLAGS += -I$(srctree)/tools/include
 TPROGS_CFLAGS += -I$(srctree)/tools/perf
+TPROGS_CFLAGS += -I$(srctree)/tools/lib
 TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0
 
 ifdef SYSROOT
@@ -314,6 +315,9 @@  XDP_SAMPLE_CFLAGS += -Wall -O2 \
 
 $(obj)/$(XDP_SAMPLE): TPROGS_CFLAGS = $(XDP_SAMPLE_CFLAGS)
 $(obj)/$(XDP_SAMPLE): $(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h
+# Override includes for trace_helpers.o because __must_check won't be defined
+# in our include path.
+$(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check=
 
 -include $(BPF_SAMPLES_PATH)/Makefile.target
 
diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
index 9d768e083714..13e618317c8b 100644
--- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
+++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
@@ -302,16 +302,18 @@  void test_fill_link_info(void)
 {
 	struct test_fill_link_info *skel;
 	int i;
+	struct ksyms *ksyms;
 
 	skel = test_fill_link_info__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "skel_open"))
 		return;
 
 	/* load kallsyms to compare the addr */
-	if (!ASSERT_OK(load_kallsyms_refresh(), "load_kallsyms_refresh"))
+	ksyms = load_kallsyms_local();
+	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_local"))
 		goto cleanup;
 
-	kprobe_addr = ksym_get_addr(KPROBE_FUNC);
+	kprobe_addr = ksym_get_addr_local(ksyms, KPROBE_FUNC);
 	if (test__start_subtest("kprobe_link_info"))
 		test_kprobe_fill_link_info(skel, BPF_PERF_EVENT_KPROBE, false);
 	if (test__start_subtest("kretprobe_link_info"))
@@ -329,7 +331,7 @@  void test_fill_link_info(void)
 
 	qsort(kmulti_syms, KMULTI_CNT, sizeof(kmulti_syms[0]), symbols_cmp_r);
 	for (i = 0; i < KMULTI_CNT; i++)
-		kmulti_addrs[i] = ksym_get_addr(kmulti_syms[i]);
+		kmulti_addrs[i] = ksym_get_addr_local(ksyms, kmulti_syms[i]);
 	if (test__start_subtest("kprobe_multi_link_info"))
 		test_kprobe_multi_fill_link_info(skel, false, false);
 	if (test__start_subtest("kretprobe_multi_link_info"))
@@ -339,4 +341,5 @@  void test_fill_link_info(void)
 
 cleanup:
 	test_fill_link_info__destroy(skel);
+	free_kallsyms_local(ksyms);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c
index 1fbe7e4ac00a..532b05ae2da4 100644
--- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_testmod_test.c
@@ -4,6 +4,8 @@ 
 #include "trace_helpers.h"
 #include "bpf/libbpf_internal.h"
 
+static struct ksyms *ksyms;
+
 static void kprobe_multi_testmod_check(struct kprobe_multi *skel)
 {
 	ASSERT_EQ(skel->bss->kprobe_testmod_test1_result, 1, "kprobe_test1_result");
@@ -50,12 +52,12 @@  static void test_testmod_attach_api_addrs(void)
 	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
 	unsigned long long addrs[3];
 
-	addrs[0] = ksym_get_addr("bpf_testmod_fentry_test1");
-	ASSERT_NEQ(addrs[0], 0, "ksym_get_addr");
-	addrs[1] = ksym_get_addr("bpf_testmod_fentry_test2");
-	ASSERT_NEQ(addrs[1], 0, "ksym_get_addr");
-	addrs[2] = ksym_get_addr("bpf_testmod_fentry_test3");
-	ASSERT_NEQ(addrs[2], 0, "ksym_get_addr");
+	addrs[0] = ksym_get_addr_local(ksyms, "bpf_testmod_fentry_test1");
+	ASSERT_NEQ(addrs[0], 0, "ksym_get_addr_local");
+	addrs[1] = ksym_get_addr_local(ksyms, "bpf_testmod_fentry_test2");
+	ASSERT_NEQ(addrs[1], 0, "ksym_get_addr_local");
+	addrs[2] = ksym_get_addr_local(ksyms, "bpf_testmod_fentry_test3");
+	ASSERT_NEQ(addrs[2], 0, "ksym_get_addr_local");
 
 	opts.addrs = (const unsigned long *) addrs;
 	opts.cnt = ARRAY_SIZE(addrs);
@@ -79,11 +81,19 @@  static void test_testmod_attach_api_syms(void)
 
 void serial_test_kprobe_multi_testmod_test(void)
 {
-	if (!ASSERT_OK(load_kallsyms_refresh(), "load_kallsyms_refresh"))
+	ksyms = load_kallsyms_local();
+	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_local"))
 		return;
 
 	if (test__start_subtest("testmod_attach_api_syms"))
 		test_testmod_attach_api_syms();
+
+	ksyms = load_kallsyms_refresh(ksyms);
+	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_refresh"))
+		return;
+
 	if (test__start_subtest("testmod_attach_api_addrs"))
 		test_testmod_attach_api_addrs();
+
+	free_kallsyms_local(ksyms);
 }
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index f83d9f65c65b..d64c4ef336e1 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -14,104 +14,171 @@ 
 #include <linux/limits.h>
 #include <libelf.h>
 #include <gelf.h>
+#include "bpf/libbpf_internal.h"
 
 #define TRACEFS_PIPE	"/sys/kernel/tracing/trace_pipe"
 #define DEBUGFS_PIPE	"/sys/kernel/debug/tracing/trace_pipe"
 
-#define MAX_SYMS 400000
-static struct ksym syms[MAX_SYMS];
-static int sym_cnt;
+struct ksyms {
+	struct ksym *syms;
+	size_t sym_cap;
+	size_t sym_cnt;
+};
+
+static struct ksyms *ksyms;
+
+static int ksyms__add_symbol(struct ksyms *ksyms, const char *name,
+							 unsigned long addr)
+{
+	void *tmp;
+
+	tmp = strdup(name);
+	if (!tmp)
+		return -ENOMEM;
+	ksyms->syms[ksyms->sym_cnt].addr = addr;
+	ksyms->syms[ksyms->sym_cnt].name = tmp;
+
+	ksyms->sym_cnt++;
+
+	return 0;
+}
+
+void free_kallsyms_local(struct ksyms *ksyms)
+{
+	unsigned int i;
+
+	if (!ksyms)
+		return;
+
+	if (!ksyms->syms) {
+		free(ksyms);
+		return;
+	}
+
+	for (i = 0; i < ksyms->sym_cnt; i++)
+		free(ksyms->syms[i].name);
+	free(ksyms->syms);
+	free(ksyms);
+}
 
 static int ksym_cmp(const void *p1, const void *p2)
 {
 	return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
 }
 
-int load_kallsyms_refresh(void)
+struct ksyms *load_kallsyms_refresh(struct ksyms *ksyms)
 {
 	FILE *f;
 	char func[256], buf[256];
 	char symbol;
 	void *addr;
-	int i = 0;
+	int ret;
 
-	sym_cnt = 0;
+	/* flush kallsyms, free the previously allocated dynamic memory */
+	free_kallsyms_local(ksyms);
 
 	f = fopen("/proc/kallsyms", "r");
 	if (!f)
-		return -ENOENT;
+		return NULL;
+
+	ksyms = calloc(1, sizeof(struct ksyms));
+	if (!ksyms)
+		return NULL;
 
 	while (fgets(buf, sizeof(buf), f)) {
 		if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
 			break;
 		if (!addr)
 			continue;
-		if (i >= MAX_SYMS)
-			return -EFBIG;
 
-		syms[i].addr = (long) addr;
-		syms[i].name = strdup(func);
-		i++;
+		ret = libbpf_ensure_mem((void **) &ksyms->syms, &ksyms->sym_cap,
+					sizeof(struct ksym), ksyms->sym_cnt + 1);
+		if (ret)
+			goto error;
+		ret = ksyms__add_symbol(ksyms, func, (unsigned long)addr);
+		if (ret)
+			goto error;
 	}
 	fclose(f);
-	sym_cnt = i;
-	qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
-	return 0;
+	qsort(ksyms->syms, ksyms->sym_cnt, sizeof(struct ksym), ksym_cmp);
+	return ksyms;
+
+error:
+	free_kallsyms_local(ksyms);
+	return NULL;
+}
+
+struct ksyms *load_kallsyms_local(void)
+{
+	return load_kallsyms_refresh(NULL);
 }
 
 int load_kallsyms(void)
 {
-	/*
-	 * This is called/used from multiplace places,
-	 * load symbols just once.
-	 */
-	if (sym_cnt)
-		return 0;
-	return load_kallsyms_refresh();
+	if (!ksyms)
+		ksyms = load_kallsyms_local();
+	return ksyms ? 0 : 1;
 }
 
-struct ksym *ksym_search(long key)
+struct ksym *ksym_search_local(struct ksyms *ksyms, long key)
 {
-	int start = 0, end = sym_cnt;
+	int start = 0, end = ksyms->sym_cnt;
 	int result;
 
+	if (!ksyms)
+		return NULL;
+
 	/* kallsyms not loaded. return NULL */
-	if (sym_cnt <= 0)
+	if (ksyms->sym_cnt <= 0)
 		return NULL;
 
 	while (start < end) {
 		size_t mid = start + (end - start) / 2;
 
-		result = key - syms[mid].addr;
+		result = key - ksyms->syms[mid].addr;
 		if (result < 0)
 			end = mid;
 		else if (result > 0)
 			start = mid + 1;
 		else
-			return &syms[mid];
+			return &ksyms->syms[mid];
 	}
 
-	if (start >= 1 && syms[start - 1].addr < key &&
-	    key < syms[start].addr)
+	if (start >= 1 && ksyms->syms[start - 1].addr < key &&
+	    key < ksyms->syms[start].addr)
 		/* valid ksym */
-		return &syms[start - 1];
+		return &ksyms->syms[start - 1];
 
 	/* out of range. return _stext */
-	return &syms[0];
+	return &ksyms->syms[0];
 }
 
-long ksym_get_addr(const char *name)
+struct ksym *ksym_search(long key)
+{
+	if (!ksyms)
+		return NULL;
+	return ksym_search_local(ksyms, key);
+}
+
+long ksym_get_addr_local(struct ksyms *ksyms, const char *name)
 {
 	int i;
 
-	for (i = 0; i < sym_cnt; i++) {
-		if (strcmp(syms[i].name, name) == 0)
-			return syms[i].addr;
+	for (i = 0; i < ksyms->sym_cnt; i++) {
+		if (strcmp(ksyms->syms[i].name, name) == 0)
+			return ksyms->syms[i].addr;
 	}
 
 	return 0;
 }
 
+long ksym_get_addr(const char *name)
+{
+	if (!ksyms)
+		return 0;
+	return ksym_get_addr_local(ksyms, name);
+}
+
 /* open kallsyms and read symbol addresses on the fly. Without caching all symbols,
  * this is faster than load + find.
  */
diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h
index 876f3e711df6..1449a107240c 100644
--- a/tools/testing/selftests/bpf/trace_helpers.h
+++ b/tools/testing/selftests/bpf/trace_helpers.h
@@ -11,13 +11,19 @@  struct ksym {
 	long addr;
 	char *name;
 };
+struct ksyms;
 
 int load_kallsyms(void);
-int load_kallsyms_refresh(void);
-
 struct ksym *ksym_search(long key);
 long ksym_get_addr(const char *name);
 
+struct ksyms *load_kallsyms_local(void);
+struct ksym *ksym_search_local(struct ksyms *ksyms, long key);
+long ksym_get_addr_local(struct ksyms *ksyms, const char *name);
+
+struct ksyms *load_kallsyms_refresh(struct ksyms *ksyms);
+void free_kallsyms_local(struct ksyms *ksyms);
+
 /* open kallsyms and find addresses on the fly, faster than load + search. */
 int kallsyms_find(const char *sym, unsigned long long *addr);