Messages in this thread Patch in this message | | | From | Padmanabha Srinivasaiah <> | Subject | [PATCH v3] kallsyms: strip CLANG CFI postfix ".cfi_jt" | Date | Thu, 29 Jul 2021 22:53:12 +0200 |
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Clang CFI adds a postfix ".cfi_jt" to a symbols of extern functions. For example 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 v3: - Modified commit message to indicate fix is for Clang CFI postfix - Rebased on recent patch from ndesaulniers@google.com. - 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 | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 5cabe4dd3ff4..67d015854cbd 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -174,7 +174,8 @@ 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) || + IS_ENABLED(CONFIG_LTO_CLANG_THIN))) return false; res = strstr(s, ".llvm."); @@ -184,16 +185,24 @@ static bool cleanup_symbol_name(char *s) } /* - * LLVM appends a hash to static function names when ThinLTO and CFI - * are both enabled, i.e. foo() becomes - * foo$707af9a22804d33c81801f27dcfe489b. This causes confusion and - * potentially breaks user space tools, so we strip the suffix from - * expanded symbol names. + * LLVM appends a hash to static function names when both + * (Thin/FULL) LTO and CFI are enabled, i.e. foo() becomes + * foo$707af9a22804d33c81801f27dcfe489b. + * + * In case of non static function symbol <funcsym>, + * the local jump table will have entry as <funcsym>.cfi_jt. + * + * This causes confusion and potentially breaks + * user space tools and some built-in components. + * So we strip the suffix from expanded symbol names. */ if (!IS_ENABLED(CONFIG_CFI_CLANG)) return false; res = strrchr(s, '$'); + if (!res) + res = strstr(s, ".cfi_jt"); + if (res) { *res = '\0'; return true; -- 2.17.1
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