Commit 17168f5c authored by Marco Elver's avatar Marco Elver Committed by Thomas Gleixner

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: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarWill Deacon <will@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200521142047.169334-3-elver@google.com

parent ea91a1d4
# SPDX-License-Identifier: GPL-2.0 # SPDX-License-Identifier: GPL-2.0
ifdef CONFIG_KCSAN 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 endif # CONFIG_KCSAN
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