Messages in this thread Patch in this message | | | From | Padmanabha Srinivasaiah <> | Subject | [PATCH v4] kallsyms: strip CLANG CFI postfix ".cfi_jt" | Date | Fri, 6 Aug 2021 01:27:38 +0200 |
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Clang CFI adds a postfix ".cfi_jt" to a symbols of extern functions. For e.g. this breaks syscall tracer that doesn't expect such postfix, so strip out the postfix from the expanded symbol.
Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy@gmail.com> --- Change in v4: - Remove redundant check; irrespective of LTO type (THIN/FULL), LTO_CLANG will be always enabled. Hence will be used as entry flag to check various postfix patterns. - And prior to stripping postfix ".cfi_jt", added a comment to justify why we are doing so. Change in v3: - Modified commit message to indicate fix is for Clang CFI postfix - Rebased on recent patch from ndesaulniers@google.com. https://lore.kernel.org/lkml/ 20210707181814.365496-1-ndesaulniers@google.com/#t - Fix is enabled even for CONFIG_LTO_CLANG
Change in v2: - Use existing routine in kallsyms to strip postfix ".cfi_jt" from extern function name. - Modified the commit message accordingly
kernel/kallsyms.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 5cabe4dd3ff4..1b40bcf20fe6 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -174,13 +174,15 @@ static bool cleanup_symbol_name(char *s) * foo.llvm.974640843467629774. This can break hooking of static * functions with kprobes. */ - if (!IS_ENABLED(CONFIG_LTO_CLANG_THIN)) + if (!IS_ENABLED(CONFIG_LTO_CLANG)) return false; - res = strstr(s, ".llvm."); - if (res) { - *res = '\0'; - return true; + if (IS_ENABLED(CONFIG_LTO_CLANG_THIN)) { + res = strstr(s, ".llvm."); + if (res) { + *res = '\0'; + return true; + } } /* @@ -194,6 +196,17 @@ static bool cleanup_symbol_name(char *s) return false; res = strrchr(s, '$'); + if (!res) { + /* + * In case of non static function symbol <funcsym>, + * the local jump table will have entry as <funcsym>.cfi_jt. + * + * Such expansion breaks some built-in components, + * e.g. syscall tracer. Hence remove postfix ".cfi_jt". + */ + res = strstr(s, ".cfi_jt"); + } + if (res) { *res = '\0'; return true; -- 2.17.1
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