Re: [PATCH v5] Kunit to check the longest symbol length

On Sun, Nov 17, 2024 at 2:59 PM Sergio González Collado sergio.collado@gmail.com wrote:

The longest length of a symbol (KSYM_NAME_LEN) was increased to 512 in the reference [1]. This patch adds kunit test suite to check the longest symbol length. These tests verify that the longest symbol length defined is supported.

This test can also help other efforts for longer symbol length, like [2].

The test suite defines two symbols, one with the longest length defined, and other one whit the longest length defined +1. In the test suite there are four tests, three positive and one negative.

The first and third tests, verify that functions with names of the created symbols, can be called or not.

The second and fourth tests, verify that the symbols are created (or not) in the kernel symbol table.

[1] https://lore.kernel.org/lkml/20220802015052.10452-6-ojeda@kernel.org/ [2] https://lore.kernel.org/lkml/20240605032120.3179157-1-song@kernel.org/

Tested-by: Martin Rodriguez Reboredo yakoyoku@gmail.com Reviewed-by: Shuah Khan skhan@linuxfoundation.org Signed-off-by: Sergio González Collado sergio.collado@gmail.com Link: https://github.com/Rust-for-Linux/linux/issues/504

Hello!

This patch is passing tests when it is built-in but it is failing when I run it as a module.

Here is the result when run as a module with "modprobe longest_symbol_kunit":

[ 30.446570] KTAP version 1 [ 30.446826] 1..1 [ 30.453560] KTAP version 1 [ 30.453785] # Subtest: longest-symbol [ 30.454376] # module: longest_symbol_kunit [ 30.457622] 1..4 [ 30.463765] ok 1 test_longest_symbol [ 30.471805] # test_longest_symbol_kallsyms: test_longest_symbol kallsyms: kprobe registered [ 30.478995] ok 2 test_longest_symbol_kallsyms [ 30.479735] ok 3 test_longest_symbol_plus1 [ 30.596269] # test_longest_symbol_plus1_kallsyms: test_longest_symbol_plus1 kallsyms: kprobe registered [ 30.602564] # test_longest_symbol_plus1_kallsyms: EXPECTATION FAILED at lib/longest_symbol_kunit.c:106 [ 30.602564] Expected longest_sym_plus1 == ((void *)0), but [ 30.602564] longest_sym_plus1 == ffffffffc01313e0 [ 30.602564] ((void *)0) == 0000000000000000 [ 30.603924] not ok 4 test_longest_symbol_plus1_kallsyms [ 30.606305] # longest-symbol: pass:3 fail:1 skip:0 total:4 [ 30.606669] # Totals: pass:3 fail:1 skip:0 total:4 [ 30.608618] not ok 1 longest-symbol

Seems the symbol name is found when run as modules?

Thanks! -Rae

---

V1 -> V2: corrected CI tests. Added fix proposed at [3]

[3] https://lore.kernel.org/lkml/Y9ES4UKl%2F+DtvAVS@gmail.com/T/#m3ef0e12bb834d0...

V2 -> V3: updated base and added MODULE_DESCRIPTION() and MODULE_AUTHOR()

V3 -> V4: add x86 mantainers, add new reference.

V4 -> V5: fixed typo, added improved description

The test execution shoud result in something like:

[20:04:35] =============== longest-symbol (4 subtests) ================
[20:04:35] [PASSED] test_longest_symbol
[20:04:35] [PASSED] test_longest_symbol_kallsyms
[20:04:35] [PASSED] test_longest_symbol_plus1
[20:04:35] [PASSED] test_longest_symbol_plus1_kallsyms
[20:04:35] ================= [PASSED] longest-symbol ==================
[20:04:35] ============================================================
[20:04:35] Testing complete. Ran 4 tests: passed: 4

But also there are two warnings like:

Symbol snnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nnng1h2i3j4k5l6m7ng1h2i3j4k5l6m7nng1h2i3j4k5l6m7ng1h2i3j4k5l6m7ne too long for kallsyms (512 >= 512).
Please increase KSYM_NAME_LEN both in kernel and kallsyms.c

Because the tests try to generate simbols of the same length as KSYM_NAME_LEN. This is the expected outcome, as defined: https://lore.kernel.org/all/20131023130753.GO29695@two.firstfloor.org/

---

arch/x86/tools/insn_decoder_test.c | 3 +- lib/Kconfig.debug | 9 +++ lib/Makefile | 2 + lib/longest_symbol_kunit.c | 125 +++++++++++++++++++++++++++++ 4 files changed, 138 insertions(+), 1 deletion(-) create mode 100644 lib/longest_symbol_kunit.c

diff --git a/arch/x86/tools/insn_decoder_test.c b/arch/x86/tools/insn_decoder_test.c index 472540aeabc2..3bde35ea4188 100644 --- a/arch/x86/tools/insn_decoder_test.c +++ b/arch/x86/tools/insn_decoder_test.c @@ -10,6 +10,7 @@ #include <assert.h> #include <unistd.h> #include <stdarg.h> +#include <linux/kallsysms.h>

#define unlikely(cond) (cond)

@@ -106,7 +107,7 @@ static void parse_args(int argc, char **argv) } }

-#define BUFSIZE 256 +#define BUFSIZE (256 + KSYM_NAME_LEN)

int main(int argc, char **argv) { diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 7312ae7c3cc5..1f3059176637 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2820,6 +2820,15 @@ config FORTIFY_KUNIT_TEST by the str*() and mem*() family of functions. For testing runtime traps of FORTIFY_SOURCE, see LKDTM's "FORTIFY_*" tests.

+config LONGEST_SYM_KUNIT_TEST

•   tristate "Test the longest symbol possible" if !KUNIT_ALL_TESTS
  

•   depends on KUNIT && KPROBES
  

•   default KUNIT_ALL_TESTS
  

•   help
  

•     Tests the longest symbol possible
  

•     If unsure, say N.
  

config HW_BREAKPOINT_KUNIT_TEST bool "Test hw_breakpoint constraints accounting" if !KUNIT_ALL_TESTS depends on HAVE_HW_BREAKPOINT diff --git a/lib/Makefile b/lib/Makefile index 773adf88af41..fc878e716825 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -389,6 +389,8 @@ CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN) obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o +obj-$(CONFIG_LONGEST_SYM_KUNIT_TEST) += longest_symbol_kunit.o +CFLAGS_longest_symbol_kunit.o += $(call cc-disable-warning, missing-prototypes)

obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o

diff --git a/lib/longest_symbol_kunit.c b/lib/longest_symbol_kunit.c new file mode 100644 index 000000000000..ebd26eedbf7b --- /dev/null +++ b/lib/longest_symbol_kunit.c @@ -0,0 +1,125 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Test the longest symbol length. Execute with:
• • ./tools/testing/kunit/kunit.py run longest-symbol
• • --arch=x86_64 --kconfig_add CONFIG_KPROBES=y --kconfig_add CONFIG_MODULES=y
• • --kconfig_add CONFIG_RETPOLINE=n --kconfig_add CONFIG_CFI_CLANG=n
• • --kconfig_add CONFIG_MITIGATION_RETPOLINE=n
• */

+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <kunit/test.h> +#include <linux/stringify.h> +#include <linux/kprobes.h> +#include <linux/kallsyms.h>

+#define DI(name) s##name##name +#define DDI(name) DI(n##name##name) +#define DDDI(name) DDI(n##name##name) +#define DDDDI(name) DDDI(n##name##name) +#define DDDDDI(name) DDDDI(n##name##name)

+#define PLUS1(name) __PASTE(name, e)

+/*Generate a symbol whose name length is 511 */ +#define LONGEST_SYM_NAME DDDDDI(g1h2i3j4k5l6m7n)

+/*Generate a symbol whose name length is 512 */ +#define LONGEST_SYM_NAME_PLUS1 PLUS1(LONGEST_SYM_NAME)

+#define RETURN_LONGEST_SYM 0xAAAAA +#define RETURN_LONGEST_SYM_PLUS1 0x55555

+noinline int LONGEST_SYM_NAME(void); +noinline int LONGEST_SYM_NAME(void) +{

•   return RETURN_LONGEST_SYM;
  

+}

+noinline int LONGEST_SYM_NAME_PLUS1(void); +noinline int LONGEST_SYM_NAME_PLUS1(void) +{

•   return RETURN_LONGEST_SYM_PLUS1;
  

+}

+_Static_assert(sizeof(__stringify(LONGEST_SYM_NAME)) == KSYM_NAME_LEN, +"Incorrect symbol length found. Expected KSYM_NAME_LEN: " +__stringify(KSYM_NAME) ", but found: " +__stringify(sizeof(LONGEST_SYM_NAME)));

+static void test_longest_symbol(struct kunit *test) +{

•   KUNIT_EXPECT_EQ(test, RETURN_LONGEST_SYM, LONGEST_SYM_NAME());
  

+};

+static void test_longest_symbol_kallsyms(struct kunit *test) +{

•   unsigned long (*kallsyms_lookup_name)(const char *name);
  

•   static int (*longest_sym)(void);
  

•   struct kprobe kp = {
  

•           .symbol_name = "kallsyms_lookup_name",
  

•   };
  

•   if (register_kprobe(&kp) < 0) {
  

•           pr_info("%s: kprobe not registered\n", __func__);
  

•           KUNIT_FAIL(test, "test_longest_symbol kallsysms: kprobe not registered\n");
  

•           return;
  

•   }
  

•   kunit_warn(test, "test_longest_symbol kallsyms: kprobe registered\n");
  

•   kallsyms_lookup_name = (unsigned long (*)(const char *name))kp.addr;
  

•   unregister_kprobe(&kp);
  

•   longest_sym =
  

•           (void *) kallsyms_lookup_name(__stringify(LONGEST_SYM_NAME));
  

•   KUNIT_EXPECT_EQ(test, RETURN_LONGEST_SYM, longest_sym());
  

+};

+static void test_longest_symbol_plus1(struct kunit *test) +{

•   KUNIT_EXPECT_EQ(test, RETURN_LONGEST_SYM_PLUS1, LONGEST_SYM_NAME_PLUS1());
  

+};

+static void test_longest_symbol_plus1_kallsyms(struct kunit *test) +{

•   unsigned long (*kallsyms_lookup_name)(const char *name);
  

•   static int (*longest_sym_plus1)(void);
  

•   struct kprobe kp = {
  

•           .symbol_name = "kallsyms_lookup_name",
  

•   };
  

•   if (register_kprobe(&kp) < 0) {
  

•           pr_info("%s: kprobe not registered\n", __func__);
  

•           KUNIT_FAIL(test, "test_longest_symbol kallsysms: kprobe not registered\n");
  

•           return;
  

•   }
  

•   kunit_warn(test, "test_longest_symbol_plus1 kallsyms: kprobe registered\n");
  

•   kallsyms_lookup_name = (unsigned long (*)(const char *name))kp.addr;
  

•   unregister_kprobe(&kp);
  

•   longest_sym_plus1 =
  

•           (void *) kallsyms_lookup_name(__stringify(LONGEST_SYM_NAME_PLUS1));
  

•   KUNIT_EXPECT_NULL(test, longest_sym_plus1);
  

+};

+static struct kunit_case longest_symbol_test_cases[] = {

•   KUNIT_CASE(test_longest_symbol),
  

•   KUNIT_CASE(test_longest_symbol_kallsyms),
  

•   KUNIT_CASE(test_longest_symbol_plus1),
  

•   KUNIT_CASE(test_longest_symbol_plus1_kallsyms),
  

•   {}
  

+};

+static struct kunit_suite longest_symbol_test_suite = {

•   .name = "longest-symbol",
  

•   .test_cases = longest_symbol_test_cases,
  

+}; +kunit_test_suite(longest_symbol_test_suite);

+MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Test the longest symbol length");

+MODULE_AUTHOR("Sergio González Collado");

2.39.2

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