Re: [PATCH v4] Kunit to check the longest symbol length

On 9/24/24 11:23, Sergio González Collado wrote:

The longest length of a symbol (KSYM_NAME_LEN) was increased to 512 in the reference [1]. This patch adds a kunit test to check the longest symbol length.

This test can also help other efforts for longer symbol lenght,

Spelling - length

Can you explain what kind of tests does it run and how it is useful? Include test output in the change log.

like [2].

[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 Signed-off-by: Sergio González Collado sergio.collado@gmail.com

---

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.

arch/x86/tools/insn_decoder_test.c | 3 +- lib/Kconfig.debug | 9 +++ lib/Makefile | 2 + lib/longest_symbol_kunit.c | 124 +++++++++++++++++++++++++++++ 4 files changed, 137 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 bc8faa4509e1..09015e7e07f3 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2805,6 +2805,15 @@ 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
  

Can you add more detail why one would want to enable this test?

•  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..557ad6eae56c --- /dev/null +++ b/lib/longest_symbol_kunit.c @@ -0,0 +1,124 @@ +// 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
• */

+#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");

base-commit: abf2050f51fdca0fd146388f83cddd95a57a008d

thanks, -- Shuah