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Message-ID: <CAP-5=fUgm63zw3Maub-JcEJyy57Bjby=jHbTzAAcGchonOamUg@mail.gmail.com>
Date: Tue, 2 Dec 2025 17:12:06 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, James Clark <james.clark@...aro.org>,
Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 5/5] perf test: Add kallsyms split test
On Tue, Dec 2, 2025 at 3:57 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Create a fake root directory for /proc/{version,modules,kallsyms} in
> /tmp for testing. The kallsyms has a bad symbol in the module and it
> causes the main map splitted. The test ensures it only has two maps -
> kernel and the module and it finds the initial map after the module
> without creating the split maps like [kernel].0 and so on.
>
> $ perf test -vv "split kallsyms"
> 69: split kallsyms:
> --- start ---
> test child forked, pid 1016196
> try to create fake root directory
> create kernel maps from the fake root directory
> maps__set_modules_path_dir: cannot open /tmp/perf-test.Zrv6Sy/lib/modules/X.Y.Z dir
> Problems setting modules path maps, continuing anyway...
> Failed to open /tmp/perf-test.Zrv6Sy/proc/kcore. Note /proc/kcore requires CAP_SYS_RAWIO capability to access.
> Using /tmp/perf-test.Zrv6Sy/proc/kallsyms for symbols
> kernel map loaded - check symbol and map
> ---- end(0) ----
> 69: split kallsyms : Ok
>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Reviewed-by: Ian Rogers <irogers@...gle.com>
Thanks,
Ian
> ---
> tools/perf/tests/Build | 1 +
> tools/perf/tests/builtin-test.c | 1 +
> tools/perf/tests/kallsyms-split.c | 156 ++++++++++++++++++++++++++++++
> tools/perf/tests/tests.h | 1 +
> 4 files changed, 159 insertions(+)
> create mode 100644 tools/perf/tests/kallsyms-split.c
>
> diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
> index af67f8ef74b49c58..c2a67ce459417e0f 100644
> --- a/tools/perf/tests/Build
> +++ b/tools/perf/tests/Build
> @@ -69,6 +69,7 @@ perf-test-y += util.o
> perf-test-y += hwmon_pmu.o
> perf-test-y += tool_pmu.o
> perf-test-y += subcmd-help.o
> +perf-test-y += kallsyms-split.o
>
> ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 arm arm64 powerpc))
> perf-test-$(CONFIG_DWARF_UNWIND) += dwarf-unwind.o
> diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> index 9090e8238a447826..bd6ffa8e4578431a 100644
> --- a/tools/perf/tests/builtin-test.c
> +++ b/tools/perf/tests/builtin-test.c
> @@ -140,6 +140,7 @@ static struct test_suite *generic_tests[] = {
> &suite__symbols,
> &suite__util,
> &suite__subcmd_help,
> + &suite__kallsyms_split,
> NULL,
> };
>
> diff --git a/tools/perf/tests/kallsyms-split.c b/tools/perf/tests/kallsyms-split.c
> new file mode 100644
> index 0000000000000000..bbbc66957e5d0453
> --- /dev/null
> +++ b/tools/perf/tests/kallsyms-split.c
> @@ -0,0 +1,156 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/compiler.h>
> +#include <fcntl.h>
> +#include <signal.h>
> +#include <unistd.h>
> +#include <sys/stat.h>
> +#include "util/dso.h"
> +#include "util/map.h"
> +#include "util/symbol.h"
> +#include "util/debug.h"
> +#include "util/machine.h"
> +#include "tests.h"
> +
> +/*
> + * This test is to check whether a bad symbol in a module won't split kallsyms maps.
> + * The main_symbol[1-3] should belong to the main [kernel.kallsyms] map even if the
> + * bad_symbol from the module is found in the middle.
> + */
> +static char root_template[] = "/tmp/perf-test.XXXXXX";
> +static char *root_dir;
> +
> +static const char proc_version[] = "Linux version X.Y.Z (just for perf test)\n";
> +static const char proc_modules[] = "module 4096 1 - Live 0xffffffffcd000000\n";
> +static const char proc_kallsyms[] =
> + "ffffffffab200000 T _stext\n"
> + "ffffffffab200010 T good_symbol\n"
> + "ffffffffab200020 t bad_symbol\n"
> + "ffffffffab200030 t main_symbol1\n"
> + "ffffffffab200040 t main_symbol2\n"
> + "ffffffffab200050 t main_symbol3\n"
> + "ffffffffab200060 T _etext\n"
> + "ffffffffcd000000 T start_module\t[module]\n"
> + "ffffffffab200020 u bad_symbol\t[module]\n"
> + "ffffffffcd000040 T end_module\t[module]\n";
> +
> +static struct {
> + const char *name;
> + const char *contents;
> + long len;
> +} proc_files[] = {
> + { "version", proc_version, sizeof(proc_version) - 1 },
> + { "modules", proc_modules, sizeof(proc_modules) - 1 },
> + { "kallsyms", proc_kallsyms, sizeof(proc_kallsyms) - 1 },
> +};
> +
> +static void remove_proc_dir(int sig __maybe_unused)
> +{
> + char buf[128];
> +
> + if (root_dir == NULL)
> + return;
> +
> + for (unsigned i = 0; i < ARRAY_SIZE(proc_files); i++) {
> + scnprintf(buf, sizeof(buf), "%s/proc/%s", root_dir, proc_files[i].name);
> + remove(buf);
> + }
> +
> + scnprintf(buf, sizeof(buf), "%s/proc", root_dir);
> + rmdir(buf);
> +
> + rmdir(root_dir);
> + root_dir = NULL;
> +}
> +
> +static int create_proc_dir(void)
> +{
> + char buf[128];
> +
> + root_dir = mkdtemp(root_template);
> + if (root_dir == NULL)
> + return -1;
> +
> + scnprintf(buf, sizeof(buf), "%s/proc", root_dir);
> + if (mkdir(buf, 0700) < 0)
> + goto err;
> +
> + for (unsigned i = 0; i < ARRAY_SIZE(proc_files); i++) {
> + int fd, len;
> +
> + scnprintf(buf, sizeof(buf), "%s/proc/%s", root_dir, proc_files[i].name);
> + fd = open(buf, O_RDWR | O_CREAT, 0600);
> + if (fd < 0)
> + goto err;
> +
> + len = write(fd, proc_files[i].contents, proc_files[i].len);
> + close(fd);
> + if (len != proc_files[i].len)
> + goto err;
> + }
> + return 0;
> +
> +err:
> + remove_proc_dir(0);
> + return -1;
> +}
> +
> +static int test__kallsyms_split(struct test_suite *test __maybe_unused,
> + int subtest __maybe_unused)
> +{
> + struct machine m;
> + struct map *map = NULL;
> + int ret = TEST_FAIL;
> +
> + pr_debug("try to create fake root directory\n");
> + if (create_proc_dir() < 0) {
> + pr_debug("SKIP: cannot create a fake root directory\n");
> + return TEST_SKIP;
> + }
> +
> + signal(SIGINT, remove_proc_dir);
> + signal(SIGPIPE, remove_proc_dir);
> + signal(SIGSEGV, remove_proc_dir);
> + signal(SIGTERM, remove_proc_dir);
> +
> + pr_debug("create kernel maps from the fake root directory\n");
> + machine__init(&m, root_dir, HOST_KERNEL_ID);
> + if (machine__create_kernel_maps(&m) < 0) {
> + pr_debug("FAIL: failed to create kernel maps\n");
> + goto out;
> + }
> +
> + /* force to use /proc/kallsyms */
> + symbol_conf.ignore_vmlinux = true;
> + symbol_conf.ignore_vmlinux_buildid = true;
> + symbol_conf.allow_aliases = true;
> +
> + if (map__load(machine__kernel_map(&m)) < 0) {
> + pr_debug("FAIL: failed to load kallsyms\n");
> + goto out;
> + }
> +
> + pr_debug("kernel map loaded - check symbol and map\n");
> + if (maps__nr_maps(machine__kernel_maps(&m)) != 2) {
> + pr_debug("FAIL: it should have the kernel and a module, but has %u maps\n",
> + maps__nr_maps(machine__kernel_maps(&m)));
> + goto out;
> + }
> +
> + if (machine__find_kernel_symbol_by_name(&m, "main_symbol3", &map) == NULL) {
> + pr_debug("FAIL: failed to find a symbol\n");
> + goto out;
> + }
> +
> + if (!RC_CHK_EQUAL(map, machine__kernel_map(&m))) {
> + pr_debug("FAIL: the symbol is not in the kernel map\n");
> + goto out;
> + }
> + ret = TEST_OK;
> +
> +out:
> + remove_proc_dir(0);
> + machine__exit(&m);
> + return ret;
> +}
> +
> +DEFINE_SUITE("split kallsyms", kallsyms_split);
> diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
> index f5fba95b6f3ffbd3..cb67ddbd03753531 100644
> --- a/tools/perf/tests/tests.h
> +++ b/tools/perf/tests/tests.h
> @@ -178,6 +178,7 @@ DECLARE_SUITE(event_groups);
> DECLARE_SUITE(symbols);
> DECLARE_SUITE(util);
> DECLARE_SUITE(subcmd_help);
> +DECLARE_SUITE(kallsyms_split);
>
> /*
> * PowerPC and S390 do not support creation of instruction breakpoints using the
> --
> 2.52.0.158.g65b55ccf14-goog
>
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