Similar to: commit 8b8e6b5d3b01 ("kallsyms: strip ThinLTO hashes from static functions") It's very common for compilers to modify the symbol name for static functions as part of optimizing transformations. That makes hooking static functions (that weren't inlined or DCE'd) with kprobes difficult. LLVM has yet another name mangling scheme used by thin LTO. Combine handling of the various schemes by truncating after the first '.'. Strip off these suffixes so that we can continue to hook such static functions. Clang releases prior to clang-13 would use '$' instead of '.'
Unified · Split
| @@ -164,26 +164,46 @@ static unsigned long kallsyms_sym_address(int idx) · 163 unmodified lines | |||
| 164 | return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; | 164 | return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; |
| 165 | } | 165 | } |
| 166 | 166 | ||
| 167 | #if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN) | 167 | static bool cleanup_symbol_name(char *s) |
| 168 | /* | ||
| 169 | * LLVM appends a hash to static function names when ThinLTO and CFI are | ||
| 170 | * both enabled, i.e. foo() becomes foo$707af9a22804d33c81801f27dcfe489b. | ||
| 171 | * This causes confusion and potentially breaks user space tools, so we | ||
| 172 | * strip the suffix from expanded symbol names. | ||
| 173 | */ | ||
| 174 | static inline bool cleanup_symbol_name(char *s) | ||
| 175 | { | 168 | { |
| 176 | char *res; | 169 | char *res; |
| 177 | 170 | ||
| 171 | if (!IS_ENABLED(CONFIG_LTO_CLANG)) | ||
| 172 | return false; | ||
| 173 | |||
| 174 | /* | ||
| 175 | * LLVM appends various suffixes for local functions and variables that | ||
| 176 | * must be promoted to global scope as part of LTO. This can break | ||
| 177 | * hooking of static functions with kprobes. '.' is not a valid | ||
| 178 | * character in an identifier in C. Suffixes observed: | ||
| 179 | * - foo.llvm.[0-9a-f]+ | ||
| 180 | * - foo.[0-9a-f]+ | ||
| 181 | * - foo.[0-9a-f]+.cfi_jt | ||
| 182 | */ | ||
| 183 | res = strchr(s, '.'); | ||
| 184 | if (res) { | ||
| 185 | *res = '\0'; | ||
| 186 | return true; | ||
| 187 | } | ||
| 188 | |||
| 189 | if (!IS_ENABLED(CONFIG_CFI_CLANG) || | ||
| 190 | !IS_ENABLED(CONFIG_LTO_CLANG_THIN) || | ||
| 191 | CONFIG_CLANG_VERSION >= 130000) | ||
| 192 | return false; | ||
| 193 | |||
| 194 | /* | ||
| 195 | * Prior to LLVM 13, the following suffixes were observed when thinLTO | ||
| 196 | * and CFI are both enabled: | ||
| 197 | * - foo$[0-9]+ | ||
| 198 | */ | ||
| 178 | res = strrchr(s, '$'); | 199 | res = strrchr(s, '$'); |
| 179 | if (res) | 200 | if (res) { |
| 180 | *res = '\0'; | 201 | *res = '\0'; |
| 202 | return true; | ||
| 203 | } | ||
| 181 | 204 | ||
| 182 | return res != NULL; | 205 | return false; |
| 183 | } | 206 | } |
| 184 | #else | ||
| 185 | static inline bool cleanup_symbol_name(char *s) { return false; } | ||
| 186 | #endif | ||
| 187 | 207 | ||
| 188 | /* Lookup the address for this symbol. Returns 0 if not found. */ | 208 | /* Lookup the address for this symbol. Returns 0 if not found. */ |
| 189 | unsigned long kallsyms_lookup_name(const char *name) | 209 | unsigned long kallsyms_lookup_name(const char *name) |