Merge tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull KCSAN updates from Paul McKenney:
 "This provides KCSAN fixes and also the ability to take memory barriers
  into account for weakly-ordered systems. This last can increase the
  probability of detecting certain types of data races"

* tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (29 commits)
  kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it
  kcsan: Avoid nested contexts reading inconsistent reorder_access
  kcsan: Turn barrier instrumentation into macros
  kcsan: Make barrier tests compatible with lockdep
  kcsan: Support WEAK_MEMORY with Clang where no objtool support exists
  compiler_attributes.h: Add __disable_sanitizer_instrumentation
  objtool, kcsan: Remove memory barrier instrumentation from noinstr
  objtool, kcsan: Add memory barrier instrumentation to whitelist
  sched, kcsan: Enable memory barrier instrumentation
  mm, kcsan: Enable barrier instrumentation
  x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock()
  x86/barriers, kcsan: Use generic instrumentation for non-smp barriers
  asm-generic/bitops, kcsan: Add instrumentation for barriers
  locking/atomics, kcsan: Add instrumentation for barriers
  locking/barriers, kcsan: Support generic instrumentation
  locking/barriers, kcsan: Add instrumentation for barriers
  kcsan: selftest: Add test case to check memory barrier instrumentation
  kcsan: Ignore GCC 11+ warnings about TSan runtime support
  kcsan: test: Add test cases for memory barrier instrumentation
  kcsan: test: Match reordered or normal accesses
  ...

2 files changed, 36 insertions, 7 deletions

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 21735829b860..a9a1f7259d62 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -849,6 +849,10 @@ static const char *uaccess_safe_builtin[] = {
 	"__asan_report_store16_noabort",
 	/* KCSAN */
 	"__kcsan_check_access",
+	"__kcsan_mb",
+	"__kcsan_wmb",
+	"__kcsan_rmb",
+	"__kcsan_release",
 	"kcsan_found_watchpoint",
 	"kcsan_setup_watchpoint",
 	"kcsan_check_scoped_accesses",
@@ -1068,11 +1072,11 @@ static void annotate_call_site(struct objtool_file *file,
 	}
 
 	/*
-	 * Many compilers cannot disable KCOV with a function attribute
-	 * so they need a little help, NOP out any KCOV calls from noinstr
-	 * text.
+	 * Many compilers cannot disable KCOV or sanitizer calls with a function
+	 * attribute so they need a little help, NOP out any such calls from
+	 * noinstr text.
 	 */
-	if (insn->sec->noinstr && sym->kcov) {
+	if (insn->sec->noinstr && sym->profiling_func) {
 		if (reloc) {
 			reloc->type = R_NONE;
 			elf_write_reloc(file->elf, reloc);
@@ -1987,6 +1991,31 @@ static int read_intra_function_calls(struct objtool_file *file)
 	return 0;
 }
 
+/*
+ * Return true if name matches an instrumentation function, where calls to that
+ * function from noinstr code can safely be removed, but compilers won't do so.
+ */
+static bool is_profiling_func(const char *name)
+{
+	/*
+	 * Many compilers cannot disable KCOV with a function attribute.
+	 */
+	if (!strncmp(name, "__sanitizer_cov_", 16))
+		return true;
+
+	/*
+	 * Some compilers currently do not remove __tsan_func_entry/exit nor
+	 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
+	 * the __no_sanitize_thread attribute, remove them. Once the kernel's
+	 * minimum Clang version is 14.0, this can be removed.
+	 */
+	if (!strncmp(name, "__tsan_func_", 12) ||
+	    !strcmp(name, "__tsan_atomic_signal_fence"))
+		return true;
+
+	return false;
+}
+
 static int classify_symbols(struct objtool_file *file)
 {
 	struct section *sec;
@@ -2007,8 +2036,8 @@ static int classify_symbols(struct objtool_file *file)
 			if (!strcmp(func->name, "__fentry__"))
 				func->fentry = true;
 
-			if (!strncmp(func->name, "__sanitizer_cov_", 16))
-				func->kcov = true;
+			if (is_profiling_func(func->name))
+				func->profiling_func = true;
 		}
 	}
 
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index cdc739fa9a6f..d22336781401 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -58,7 +58,7 @@ struct symbol {
 	u8 static_call_tramp : 1;
 	u8 retpoline_thunk   : 1;
 	u8 fentry            : 1;
-	u8 kcov              : 1;
+	u8 profiling_func    : 1;
 	struct list_head pv_target;
 };