7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf [ Upstream commit ac323c9467092479dc1e5bc138c9abbe015b0069 ] Adding a line of code to __link_shadow_page() with a literal string causes a false positive changed function with GCC: arch/x86/kvm/kvm.ko.o: changed function: kvm_tdp_mmu_map_private_pfn While the patch only touched __link_shadow_page(), the string addition triggered a rename of .LC64 -> .LC65 in kvm_tdp_mmu_map_private_pfn() even though the underlying referenced constant data didn't change. So for .LC* symbols, the suffix is arbitrary but the data isn't. Add the underlying data to the checksum calculation rather than the symbol name. Clang also uses .LC* symbols, but also uses anonymous data. Both compilers put this data in .rodata.cst sections. Fixes: 0d83da43b1e1 ("objtool/klp: Add --checksum option to generate per-function checksums") Link: https://patch.msgid.link/f3a9e74ceebc6475ce94bcfe985401140857814a.1787939301.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf Signed-off-by: Sasha Levin --- tools/objtool/klp-checksum.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/tools/objtool/klp-checksum.c b/tools/objtool/klp-checksum.c index b8e47f28997e9..ebe25f9c5260a 100644 --- a/tools/objtool/klp-checksum.c +++ b/tools/objtool/klp-checksum.c @@ -54,6 +54,19 @@ static int checksum_debug_init(struct objtool_file *file) return 0; } +/* + * Detect a reference to anonymous constant pool data which the compiler places + * in .rodata.cst and which either has an .LC symbol associated with + * it or (with Clang) no symbol at all. These are typically initializers for + * local function stack data, so they're considered part of the function rather + * than data per se. + */ +static bool is_anonymous_const_data(struct symbol *sym) +{ + return strstarts(sym->sec->name, ".rodata.cst") && + (is_sec_sym(sym) || strstarts(sym->name, ".LC")); +} + static void checksum_update_insn(struct objtool_file *file, struct symbol *func, struct instruction *insn) { @@ -129,6 +142,14 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func, goto alts; } + if (is_anonymous_const_data(sym)) { + void *cst; + + cst = sym->sec->data->d_buf + sym->offset + offset; + __checksum_update_insn(func, insn, cst, sym->sec->sh.sh_entsize); + goto alts; + } + if (is_sec_sym(sym)) { sym = find_symbol_containing(reloc->sym->sec, offset); if (!sym) -- 2.53.0