On Mon, Feb 17, 2025 at 3:30 PM Sergio González Collado <sergio.collado@xxxxxxxxx> wrote: > > Hello, > > On Fri, 7 Feb 2025 at 22:54, Rae Moar <rmoar@xxxxxxxxxx> wrote: > > > > On Sun, Feb 2, 2025 at 2:24 PM Sergio González Collado > > <sergio.collado@xxxxxxxxx> 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 one symbol with the longest possible length. > > > > > > The first test verify that functions with names of the created > > > symbol, can be called or not. > > > > > > The second test, verify that the symbols are created (or > > > not) in the kernel symbol table. > > > > > > [1] https://lore.kernel.org/lkml/20220802015052.10452-6-ojeda@xxxxxxxxxx/ > > > [2] https://lore.kernel.org/lkml/20240605032120.3179157-1-song@xxxxxxxxxx/ > > > > > > Tested-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx> > > > Reviewed-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> > > > Reviewed-by: Rae Moar <rmoar@xxxxxxxxxx> > > > Signed-off-by: Sergio González Collado <sergio.collado@xxxxxxxxx> > > > Link: https://github.com/Rust-for-Linux/linux/issues/504 > > > > Hello! > > > > Thanks for fixing the typo and this new version! This patch still does > > not apply cleanly in the Makefile for me. Have you rebased it on the > > kselftest/kunit branch? I also have a few more questions that I just > > noticed. > > > > Thanks! > > -Rae > > > > > --- > > > V7 -> V8: typo fixed & rebased > > > --- > > > V6 -> V7: rebased > > > --- > > > V5 -> V6: remove tests with symbols of length KSYM_NAME_LEN+1 > > > --- > > > V4 -> V5: fixed typo, added improved description > > > --- > > > V3 -> V4: add x86 mantainers, add new reference. > > > --- > > > V2 -> V3: updated base and added MODULE_DESCRIPTION() and MODULE_AUTHOR() > > > --- > > > V1 -> V2: corrected CI tests. Added fix proposed at [3] > > > > > > [3] https://lore.kernel.org/lkml/Y9ES4UKl%2F+DtvAVS@xxxxxxxxx/T/#m3ef0e12bb834d01ed1ebdcae12ef5f2add342077 > > > > > > The test execution should 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] longest-symbol ================== > > > [20:04:35] ============================================================ > > > [20:04:35] Testing complete. Ran 4 tests: passed: 4 > > > ``` > > > --- > > > arch/x86/tools/insn_decoder_test.c | 3 +- > > > lib/Kconfig.debug | 9 ++++ > > > lib/Makefile | 2 + > > > lib/longest_symbol_kunit.c | 84 ++++++++++++++++++++++++++++++ > > > 4 files changed, 97 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..6c2986d2ad11 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/kallsyms.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) > > > > I'm not too familiar with this test. I believe this would potentially > > make a symbol with a length that exceeds the KSYM_NAME_LEN. What is > > the intention for this line? > That will define how much space to write a symbol. I'm also not > familiar with that test, but I know had to be fixed: > https://lore.kernel.org/lkml/Y9ES4UKl%2F+DtvAVS@xxxxxxxxx/T/#m3ef0e12bb834d01ed1ebdcae12ef5f2add342077 > > > > > > > > > int main(int argc, char **argv) > > > { > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > index 1af972a92d06..62d43aa9e8f0 100644 > > > --- a/lib/Kconfig.debug > > > +++ b/lib/Kconfig.debug > > > @@ -2838,6 +2838,15 @@ 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 d5cfc7afbbb8..e8fec9defec2 100644 > > > --- a/lib/Makefile > > > +++ b/lib/Makefile > > > @@ -393,6 +393,8 @@ obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o > > > obj-$(CONFIG_CRC_KUNIT_TEST) += crc_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 > > > > These are the lines that are causing the patch to not apply cleanly. > > The change list that applies cleanly for me is: > > > > 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_CRC16_KUNIT_TEST) += crc16_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 > > > I will create a new rebased version of the patch. > > > > > > > diff --git a/lib/longest_symbol_kunit.c b/lib/longest_symbol_kunit.c > > > new file mode 100644 > > > index 000000000000..2a2dd1151097 > > > --- /dev/null > > > +++ b/lib/longest_symbol_kunit.c > > > @@ -0,0 +1,84 @@ > > > +// 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 > > > > I don't believe you use this macro. Could probably be deleted. > > > This macro should work out of the box by means of the pr_*() macros: > https://docs.kernel.org/core-api/printk-basics.html#c.pr_fmt Hi! Thanks for your responses. This seems good to me. Thanks for the explanation. > > > > > > + > > > +#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) > > > > I don't think you use this anymore with the new changes. Can probably > > be deleted. > > > Indeed, I totally overlooked that. > > > > > > + > > > +/*Generate a symbol whose name length is 511 */ > > > +#define LONGEST_SYM_NAME DDDDDI(g1h2i3j4k5l6m7n) > > > + > > > +#define RETURN_LONGEST_SYM 0xAAAAA > > > + > > > +noinline int LONGEST_SYM_NAME(void); > > > +noinline int LONGEST_SYM_NAME(void) > > > +{ > > > + return RETURN_LONGEST_SYM; > > > +} > > > + > > > +_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))); > > > > Should this error return __stringify(KSYM_NAME_LEN) instead of > > __stringify(KSYM_NAME) to give the maximum length? > > > It is done on purpose to show what the actual symbol is. Under some > conditions the names can incorporate > prefix symbols, for example: > https://lore.kernel.org/lkml/20221028194453.526899822@xxxxxxxxxxxxx/, > if this happens it will be easier to spot what is going on. Right now this outputs: "Incorrect symbol len. Expected KSYM_NAME_LEN: KSYM_NAME, but found: sizeof(snn...6m7n)" This seems incorrect because KSYM_NAME has no value. Instead I would expect: "Incorrect symbol len. Expected KSYM_NAME_LEN: 512, but found: sizeof(snn...6m7n)". > > > > > Also, I get an error because the length of LONGEST_SYM_NAME is 512. > > The error is produced by this code: > > https://elixir.bootlin.com/linux/v6.13.1/source/scripts/kallsyms.c#L152 > > and alerts if the symbol length is >= to KSYM_NAME_LEN. That is fine > > as long as that is the intention of this test to produce a warning. Or > > should this warning change to be "> KSYM_NAME_LEN" if usage of symbols > > that are the maximum length is allowed? > > > Indeed that is expected, as the limit is reached. I think it may not > be really needed to update the condition to "> KSYM_NAME_LEN". > That seems good to me. Thanks! -Rae > > Thanks a lot for your remarks. > Cheers!
