[PATCH -rcu/kcsan 23/23] objtool, kcsan: Remove memory barrier instrumentation from noinstr
From: Marco Elver <elver@google.com>
Date: 2021-10-05 11:03:58
Also in:
linux-arch, linux-doc, linux-kbuild, lkml
Subsystem:
objtool, the rest · Maintainers:
Josh Poimboeuf, Peter Zijlstra, Linus Torvalds
Teach objtool to turn instrumentation required for memory barrier modeling into nops in noinstr text. The __tsan_func_entry/exit calls are still emitted by compilers even with the __no_sanitize_thread attribute. The memory barrier instrumentation will be inserted explicitly (without compiler help), and thus needs to also explicitly be removed. Signed-off-by: Marco Elver <elver@google.com> --- tools/objtool/check.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7e8cd3ba5482..7b694e639164 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c@@ -965,6 +965,31 @@ static struct symbol *find_call_destination(struct section *sec, unsigned long o return call_dest; } +static bool should_remove_if_noinstr(const char *name) +{ + /* + * Many compilers cannot disable KCOV with a function attribute so they + * need a little help, NOP out any KCOV calls from noinstr text. + */ + if (!strncmp(name, "__sanitizer_cov_", 16)) + return true; + + /* + * Compilers currently do not remove __tsan_func_entry/exit with the + * __no_sanitize_thread attribute, remove them. Memory barrier + * instrumentation is not emitted by the compiler, but inserted + * explicitly, so we need to also remove them. + */ + if (!strncmp(name, "__tsan_func_", 12) || + !strcmp(name, "__kcsan_mb") || + !strcmp(name, "__kcsan_wmb") || + !strcmp(name, "__kcsan_rmb") || + !strcmp(name, "__kcsan_release")) + return true; + + return false; +} + /* * Find the destination instructions for all calls. */
@@ -1031,13 +1056,8 @@ static int add_call_destinations(struct objtool_file *file) &file->static_call_list); } - /* - * Many compilers cannot disable KCOV with a function attribute - * so they need a little help, NOP out any KCOV calls from noinstr - * text. - */ if (insn->sec->noinstr && - !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) { + should_remove_if_noinstr(insn->call_dest->name)) { if (reloc) { reloc->type = R_NONE; elf_write_reloc(file->elf, reloc);
--
2.33.0.800.g4c38ced690-goog