From 0837fa5ef2e562e27748e2a4552586919fce9280 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 21 May 2020 16:20:38 +0200 Subject: [PATCH] kcsan: Avoid inserting __tsan_func_entry/exit if possible To avoid inserting __tsan_func_{entry,exit}, add option if supported by compiler. Currently only Clang can be told to not emit calls to these functions. It is safe to not emit these, since KCSAN does not rely on them. Note that, if we disable __tsan_func_{entry,exit}(), we need to disable tail-call optimization in sanitized compilation units, as otherwise we may skip frames in the stack trace; in particular when the tail called function is one of the KCSAN's runtime functions, and a report is generated, we might miss the function where the actual access occurred. Since __tsan_func_{entry,exit}() insertion effectively disabled tail-call optimization, there should be no observable change. This was caught and confirmed with kcsan-test & UNWINDER_ORC. Signed-off-by: Marco Elver Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Acked-by: Will Deacon Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200521142047.169334-3-elver@google.com --- scripts/Makefile.kcsan | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan index caf1111a28ae5..20337a7ecf540 100644 --- a/scripts/Makefile.kcsan +++ b/scripts/Makefile.kcsan @@ -1,6 +1,15 @@ # SPDX-License-Identifier: GPL-2.0 ifdef CONFIG_KCSAN -CFLAGS_KCSAN := -fsanitize=thread +# GCC and Clang accept backend options differently. Do not wrap in cc-option, +# because Clang accepts "--param" even if it is unused. +ifdef CONFIG_CC_IS_CLANG +cc-param = -mllvm -$(1) +else +cc-param = --param -$(1) +endif + +CFLAGS_KCSAN := -fsanitize=thread \ + $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) endif # CONFIG_KCSAN -- 2.39.5