kernel/linux.git/scripts/kallsyms.c, branch v6.6.132

scripts/kallsyms: Fix build failure by setting errno before calling getline()

2023-07-29T06:57:32+00:00

getline() returns -1 at EOF as well as on error. It also doesn't set errno to 0 on success, so initialize it to 0 before using errno to check for an error condition. See the paragraph here [1]: For some system calls and library functions (e.g., getpriority(2)), -1 is a valid return on success. In such cases, a successful return can be distinguished from an error return by setting errno to zero before the call, and then, if the call returns a status that indicates that an error may have occurred, checking to see if errno has a nonzero value. Bear has a bug [2] that launches processes with errno set and causes the following build failure: $ bear -- make LLVM=1 ... LD .tmp_vmlinux.kallsyms1 NM .tmp_vmlinux.kallsyms1.syms KSYMS .tmp_vmlinux.kallsyms1.S read_symbol: Invalid argument [1]: https://linux.die.net/man/3/errno [2]: https://github.com/rizsotto/Bear/issues/469 Fixes: 1c975da56a6f ("scripts/kallsyms: remove KSYM_NAME_LEN_BUFFER") Reviewed-by: Miguel Ojeda Signed-off-by: James Clark Signed-off-by: Masahiro Yamada

kallsyms: strip LTO-only suffixes from promoted global functions

2023-07-12T22:39:34+00:00

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

scripts/kallsyms: remove KSYM_NAME_LEN_BUFFER

2023-06-14T19:47:04+00:00

You do not need to decide the buffer size statically. Use getline() to grow the line buffer as needed. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

scripts/kallsyms: constify long_options

2023-06-14T19:47:04+00:00

getopt_long() does not modify this. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

scripts/kallsyms: update the usage in the comment block

2023-04-17T02:03:56+00:00

Commit 010a0aad39fc ("kallsyms: Correctly sequence symbols when CONFIG_LTO_CLANG=y") added --lto-clang, and updated the usage() function, but not the comment. Update it in the same way. Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers

scripts/kallsyms: decrease expand_symbol() / cleanup_symbol_name() calls

2023-04-17T02:03:56+00:00

Currently, expand_symbol() is called many times to get the uncompressed symbol names for sorting, and also for adding comments. With the output order shuffled in the previous commit, the symbol data are now written in the following order: (1) kallsyms_num_syms (2) kallsyms_names <-- need compressed names (3) kallsyms_markers (4) kallsyms_token_table (5) kallsyms_token_index (6) kallsyms_addressed / kallsyms_offsets <-- need uncompressed names (for commenting) (7) kallsyms_relative_base (8) kallsyms_seq_of_names <-- need uncompressed names (for sorting) The compressed names are only needed by (2). Call expand_symbol() between (2) and (3) to restore the original symbol names. This requires just one expand_symbol() call for each symbol. Call cleanup_symbol_name() between (7) and (8) instead of during sorting. It is allowed to overwrite the ->sym field because (8) just outputs the index instead of the name of each symbol. Again, this requires just one cleanup_symbol_name() call for each symbol. This refactoring makes it ~30% faster. [Before] $ time scripts/kallsyms --all-symbols --absolute-percpu --base-relative \ .tmp_vmlinux.kallsyms2.syms >/dev/null real 0m1.027s user 0m1.010s sys 0m0.016s [After] $ time scripts/kallsyms --all-symbols --absolute-percpu --base-relative \ .tmp_vmlinux.kallsyms2.syms >/dev/null real 0m0.717s user 0m0.717s sys 0m0.000s Signed-off-by: Masahiro Yamada

scripts/kallsyms: change the output order

2023-04-17T02:03:56+00:00

Currently, this tool outputs symbol data in the following order. (1) kallsyms_addressed / kallsyms_offsets (2) kallsyms_relative_base (3) kallsyms_num_syms (4) kallsyms_names (5) kallsyms_markers (6) kallsyms_seq_of_names (7) kallsyms_token_table (8) kallsyms_token_index This commit changes the order as follows: (1) kallsyms_num_syms (2) kallsyms_names (3) kallsyms_markers (4) kallsyms_token_table (5) kallsyms_token_index (6) kallsyms_addressed / kallsyms_offsets (7) kallsyms_relative_base (8) kallsyms_seq_of_names The motivation is to decrease the number of function calls to expand_symbol() and cleanup_symbol_name(). The compressed names are only required for writing 'kallsyms_names'. If you do this first, we can restore the original symbol names. You do not need to repeat the same operation over again. The actual refactoring will happen in the next commit. Signed-off-by: Masahiro Yamada

scripts/kallsyms: move compiler-generated symbol patterns to mksysmap

2023-04-17T02:03:56+00:00

scripts/kallsyms.c maintains compiler-generated symbols, but we end up with something similar in scripts/mksysmap to avoid the "Inconsistent kallsyms data" error. For example, commit c17a2538704f ("mksysmap: Fix the mismatch of 'L0' symbols in System.map"). They were separately maintained prior to commit 94ff2f63d6a3 ("kbuild: reuse mksysmap output for kallsyms"). Now that scripts/kallsyms.c parses the output of scripts/mksysmap, it makes more sense to collect all the ignored patterns to mksysmap. Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers

scripts/kallsyms: exclude symbols generated by itself dynamically

2023-04-17T02:03:56+00:00

Drop the symbols generated by scripts/kallsyms itself automatically instead of maintaining the symbol list manually. Pass the kallsyms object from the previous kallsyms step (if it exists) as the third parameter of scripts/mksysmap, which will weed out the generated symbols from the input to the next kallsyms step. Signed-off-by: Masahiro Yamada

scripts/kallsyms: remove redundant code for omitting U and N

2023-04-17T02:03:56+00:00

The symbol types 'U' and 'N' are already filtered out by the following line in scripts/mksysmap: -e ' [aNUw] ' Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers