linux/kernel/kallsyms.c, branch v6.7

kallsyms: Change func signature for cleanup_symbol_name()

2023-08-25T22:00:36Z

All users of cleanup_symbol_name() do not use the return value. So let us change the return value of cleanup_symbol_name() to 'void' to reflect its usage pattern. Suggested-by: Nick Desaulniers Signed-off-by: Yonghong Song Reviewed-by: Nick Desaulniers Reviewed-by: Song Liu Link: https://lore.kernel.org/r/20230825202036.441212-1-yonghong.song@linux.dev Signed-off-by: Kees Cook

kallsyms: Fix kallsyms_selftest failure

2023-08-25T17:44:20Z

Kernel test robot reported a kallsyms_test failure when clang lto is enabled (thin or full) and CONFIG_KALLSYMS_SELFTEST is also enabled. I can reproduce in my local environment with the following error message with thin lto: [ 1.877897] kallsyms_selftest: Test for 1750th symbol failed: (tsc_cs_mark_unstable) addr=ffffffff81038090 [ 1.877901] kallsyms_selftest: abort It appears that commit 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions") caused the failure. Commit 8cc32a9bbf29 changed cleanup_symbol_name() based on ".llvm." instead of '.' where ".llvm." is appended to a before-lto-optimization local symbol name. We need to propagate such knowledge in kallsyms_selftest.c as well. Further more, compare_symbol_name() in kallsyms.c needs change as well. In scripts/kallsyms.c, kallsyms_names and kallsyms_seqs_of_names are used to record symbol names themselves and index to symbol names respectively. For example: kallsyms_names: ... __amd_smn_rw._entry <== seq 1000 __amd_smn_rw._entry.5 <== seq 1001 __amd_smn_rw.llvm. <== seq 1002 ... kallsyms_seqs_of_names are sorted based on cleanup_symbol_name() through, so the order in kallsyms_seqs_of_names actually has index 1000: seq 1002 <== __amd_smn_rw.llvm. (actual symbol comparison using '__amd_smn_rw') index 1001: seq 1000 <== __amd_smn_rw._entry index 1002: seq 1001 <== __amd_smn_rw._entry.5 Let us say at a particular point, at index 1000, symbol '__amd_smn_rw.llvm.' is comparing to '__amd_smn_rw._entry' where '__amd_smn_rw._entry' is the one to search e.g., with function kallsyms_on_each_match_symbol(). The current implementation will find out '__amd_smn_rw._entry' is less than '__amd_smn_rw.llvm.' and then continue to search e.g., index 999 and never found a match although the actual index 1001 is a match. To fix this issue, let us do cleanup_symbol_name() first and then do comparison. In the above case, comparing '__amd_smn_rw' vs '__amd_smn_rw._entry' and '__amd_smn_rw._entry' being greater than '__amd_smn_rw', the next comparison will be > index 1000 and eventually index 1001 will be hit an a match is found. For any symbols not having '.llvm.' substr, there is no functionality change for compare_symbol_name(). Fixes: 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202308232200.1c932a90-oliver.sang@intel.com Signed-off-by: Yonghong Song Reviewed-by: Song Liu Reviewed-by: Zhen Lei Link: https://lore.kernel.org/r/20230825034659.1037627-1-yonghong.song@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Kees Cook

kallsyms: strip LTO-only suffixes from promoted global functions

2023-07-12T22:39:34Z

Commit 6eb4bd92c1ce ("kallsyms: strip LTO suffixes from static functions") stripped all function/variable suffixes started with '.' regardless of whether those suffixes are generated at LTO mode or not. In fact, as far as I know, in LTO mode, when a static function/variable is promoted to the global scope, '.llvm.<...>' suffix is added. The existing mechanism breaks live patch for a LTO kernel even if no .llvm.<...> symbols are involved. For example, for the following kernel symbols: $ grep bpf_verifier_vlog /proc/kallsyms ffffffff81549f60 t bpf_verifier_vlog ffffffff8268b430 d bpf_verifier_vlog._entry ffffffff8282a958 d bpf_verifier_vlog._entry_ptr ffffffff82e12a1f d bpf_verifier_vlog.__already_done 'bpf_verifier_vlog' is a static function. '_entry', '_entry_ptr' and '__already_done' are static variables used inside 'bpf_verifier_vlog', so llvm promotes them to file-level static with prefix 'bpf_verifier_vlog.'. Note that the func-level to file-level static function promotion also happens without LTO. Given a symbol name 'bpf_verifier_vlog', with LTO kernel, current mechanism will return 4 symbols to live patch subsystem which current live patching subsystem cannot handle it. With non-LTO kernel, only one symbol is returned. In [1], we have a lengthy discussion, the suggestion is to separate two cases: (1). new symbols with suffix which are generated regardless of whether LTO is enabled or not, and (2). new symbols with suffix generated only when LTO is enabled. The cleanup_symbol_name() should only remove suffixes for case (2). Case (1) should not be changed so it can work uniformly with or without LTO. This patch removed LTO-only suffix '.llvm.<...>' so live patching and tracing should work the same way for non-LTO kernel. The cleanup_symbol_name() in scripts/kallsyms.c is also changed to have the same filtering pattern so both kernel and kallsyms tool have the same expectation on the order of symbols. [1] https://lore.kernel.org/live-patching/20230615170048.2382735-1-song@kernel.org/T/#u Fixes: 6eb4bd92c1ce ("kallsyms: strip LTO suffixes from static functions") Reported-by: Song Liu Signed-off-by: Yonghong Song Reviewed-by: Zhen Lei Reviewed-by: Nick Desaulniers Acked-by: Song Liu Link: https://lore.kernel.org/r/20230628181926.4102448-1-yhs@fb.com Signed-off-by: Kees Cook

Merge tag 'v6.5-rc1-modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

2023-06-28T22:51:08Z

Pull module updates from Luis Chamberlain: "The changes queued up for modules are pretty tame, mostly code removal of moving of code. Only two minor functional changes are made, the only one which stands out is Sebastian Andrzej Siewior's simplification of module reference counting by removing preempt_disable() and that has been tested on linux-next for well over a month without no regressions. I'm now, I guess, also a kitchen sink for some kallsyms changes" [ There was a mis-communication about the concurrent module load changes that I had expected to come through Luis despite me authoring the patch. So some of the module updates were left hanging in the email ether, and I just committed them separately. It's my bad - I should have made it more clear that I expected my own patches to come through the module tree too. Now they missed linux-next, but hopefully that won't cause any issues - Linus ] * tag 'v6.5-rc1-modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: kallsyms: make kallsyms_show_value() as generic function kallsyms: move kallsyms_show_value() out of kallsyms.c kallsyms: remove unsed API lookup_symbol_attrs kallsyms: remove unused arch_get_kallsym() helper module: Remove preempt_disable() from module reference counting.

kallsyms: Replace all non-returning strlcpy with strscpy

2023-06-14T19:27:38Z

strlcpy() reads the entire source buffer first. This read may exceed the destination size limit. This is both inefficient and can lead to linear read overflows if a source string is not NUL-terminated [1]. In an effort to remove strlcpy() completely [2], replace strlcpy() here with strscpy(). No return values were used, so direct replacement is safe. [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [2] https://github.com/KSPP/linux/issues/89 Signed-off-by: Azeem Shaikh Reviewed-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20230614010354.1026096-1-azeemshaikh38@gmail.com

kallsyms: move kallsyms_show_value() out of kallsyms.c

2023-06-08T19:27:20Z

function kallsyms_show_value() is used by other parts like modules_open(), kprobes_read() etc. which can work in case of !KALLSYMS also. e.g. as of now lsmod do not show module address if KALLSYMS is disabled. since kallsyms_show_value() defination is not present, it returns false in !KALLSYMS. / # lsmod test 12288 0 - Live 0x0000000000000000 (O) So kallsyms_show_value() can be made generic without dependency on KALLSYMS. Thus moving out function to a new file ksyms_common.c. With this patch code is just moved to new file and no functional change. Co-developed-by: Onkarnath Signed-off-by: Onkarnath Signed-off-by: Maninder Singh Reviewed-by: Zhen Lei Signed-off-by: Luis Chamberlain

kallsyms: remove unsed API lookup_symbol_attrs

2023-05-26T22:10:18Z

with commit '7878c231dae0 ("slab: remove /proc/slab_allocators")' lookup_symbol_attrs usage is removed. Thus removing redundant API. Signed-off-by: Maninder Singh Reviewed-by: Kees Cook Signed-off-by: Luis Chamberlain

kallsyms: remove unused arch_get_kallsym() helper

2023-05-26T17:38:23Z

The arch_get_kallsym() function was introduced so that x86 could override it, but that override was removed in bf904d2762ee ("x86/pti/64: Remove the SYSCALL64 entry trampoline"), so now this does nothing except causing a warning about a missing prototype: kernel/kallsyms.c:662:12: error: no previous prototype for 'arch_get_kallsym' [-Werror=missing-prototypes] 662 | int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, Restore the old behavior before d83212d5dd67 ("kallsyms, x86: Export addresses of PTI entry trampolines") to simplify the code and avoid the warning. Signed-off-by: Arnd Bergmann Tested-by: Alan Maguire [mcgrof: fold in bpf selftest fix] Signed-off-by: Luis Chamberlain

kallsyms: Delete an unused parameter related to {module_}kallsyms_on_each_symbol()

2023-03-19T20:27:19Z

The parameter 'struct module *' in the hook function associated with {module_}kallsyms_on_each_symbol() is no longer used. Delete it. Suggested-by: Petr Mladek Signed-off-by: Zhen Lei Reviewed-by: Vincenzo Palazzo Acked-by: Jiri Olsa Acked-by: Steven Rostedt (Google) Signed-off-by: Luis Chamberlain

kallsyms: Add self-test facility

2022-11-15T08:42:02Z

Added test cases for basic functions and performance of functions kallsyms_lookup_name(), kallsyms_on_each_symbol() and kallsyms_on_each_match_symbol(). It also calculates the compression rate of the kallsyms compression algorithm for the current symbol set. The basic functions test begins by testing a set of symbols whose address values are known. Then, traverse all symbol addresses and find the corresponding symbol name based on the address. It's impossible to determine whether these addresses are correct, but we can use the above three functions along with the addresses to test each other. Due to the traversal operation of kallsyms_on_each_symbol() is too slow, only 60 symbols can be tested in one second, so let it test on average once every 128 symbols. The other two functions validate all symbols. If the basic functions test is passed, print only performance test results. If the test fails, print error information, but do not perform subsequent performance tests. Start self-test automatically after system startup if CONFIG_KALLSYMS_SELFTEST=y. Example of output content: (prefix 'kallsyms_selftest:' is omitted start --------------------------------------------------------- | nr_symbols | compressed size | original size | ratio(%) | |---------------------------------------------------------| | 107543 | 1357912 | 2407433 | 56.40 | --------------------------------------------------------- kallsyms_lookup_name() looked up 107543 symbols The time spent on each symbol is (ns): min=630, max=35295, avg=7353 kallsyms_on_each_symbol() traverse all: 11782628 ns kallsyms_on_each_match_symbol() traverse all: 9261 ns finish Signed-off-by: Zhen Lei Signed-off-by: Luis Chamberlain