Re: [PATCH for 5.2 12/12] rseq/selftests: add -no-integrated-as for clang

----- On Apr 29, 2019, at 1:03 PM, ndesaulniers ndesaulniers@google.com wrote:

On Mon, Apr 29, 2019 at 8:29 AM Mathieu Desnoyers
[off-list ref] wrote:

quoted

Ongoing work for asm goto support from clang requires the
-no-integrated-as compiler flag.

This compiler flag is present in the toplevel kernel Makefile,
but is not replicated for selftests. Add it specifically for
the rseq selftest which requires asm goto.

Link: https://reviews.llvm.org/D56571
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Nick Desaulniers <ndesaulniers@google.com>
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---
 tools/testing/selftests/rseq/Makefile | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/Makefile

b/tools/testing/selftests/rseq/Makefile
index c30c52e1d0d2..d6469535630a 100644

--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile

@@ -1,5 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0+ OR MIT
-CFLAGS += -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./
+
+ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
+CLANG_FLAGS += -no-integrated-as
+endif
+
+CFLAGS += -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./ \
+         $(CLANG_FLAGS)

The top level Makefile exports $(CLANG_FLAGS), which should contain
`-no-integrated-as`.  Is that available here?  If so, then you can
just add `$(CLANG_FLAGS)`, no compiler check needed.

AFAIU, the makefiles under tools/testing/selftests all end up including
tools/testing/selftests/lib.mk, which states:

"# This mimics the top-level Makefile. We do it explicitly here so that this
 # Makefile can operate with or without the kbuild infrastructure."

So I don't think it's using any of the definitions from the toplevel
Makefile.

If not, maybe the test for CONFIG_CC_IS_CLANG is cleaner?

A quick test indicates that the toplevel CONFIG_* definitions are unavailable
from the kernel selftests makefiles.

Thanks for the patch, and helping test asm goto in Clang!

You're very welcome! Considering that I intend to have rseq widely adopted in
user-space, it's only natural to consider that its user-space side needs to be
compiled by clang as well.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com