The "bti" selftests are built with -nostdlib, which apparently automatically creates a statically linked binary, which is what we want and need for BTI (to avoid interactions with the dynamic linker).
However this is not true when building a PIE binary, which some toolchains (Ubuntu) configure as the default. When compiling btitest with such a toolchain, it will create a dynamically linked binary, which will probably fail some tests, as the dynamic linker might not support BTI: =================== TAP version 13 1..18 not ok 1 nohint_func/call_using_br_x0 not ok 2 nohint_func/call_using_br_x16 not ok 3 nohint_func/call_using_blr .... ===================
To make sure we create static binaries, add an explicit -static on the linker command line. This forces static linking even if the toolchain defaults to PIE builds, and fixes btitest runs on BTI enabled machines.
Signed-off-by: Andre Przywara andre.przywara@arm.com --- tools/testing/selftests/arm64/bti/Makefile | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/arm64/bti/Makefile b/tools/testing/selftests/arm64/bti/Makefile index 73e013c082a65..dafa1c2aa5c47 100644 --- a/tools/testing/selftests/arm64/bti/Makefile +++ b/tools/testing/selftests/arm64/bti/Makefile @@ -39,7 +39,7 @@ BTI_OBJS = \ teststubs-bti.o \ trampoline-bti.o gen/btitest: $(BTI_OBJS) - $(CC) $(CFLAGS_BTI) $(CFLAGS_COMMON) -nostdlib -o $@ $^ + $(CC) $(CFLAGS_BTI) $(CFLAGS_COMMON) -nostdlib -static -o $@ $^
NOBTI_OBJS = \ test-nobti.o \ @@ -50,7 +50,7 @@ NOBTI_OBJS = \ teststubs-nobti.o \ trampoline-nobti.o gen/nobtitest: $(NOBTI_OBJS) - $(CC) $(CFLAGS_BTI) $(CFLAGS_COMMON) -nostdlib -o $@ $^ + $(CC) $(CFLAGS_BTI) $(CFLAGS_COMMON) -nostdlib -static -o $@ $^
# Including KSFT lib.mk here will also mangle the TEST_GEN_PROGS list # to account for any OUTPUT target-dirs optionally provided by
On Wed, May 11, 2022 at 06:21:29PM +0100, Andre Przywara wrote:
The "bti" selftests are built with -nostdlib, which apparently automatically creates a statically linked binary, which is what we want and need for BTI (to avoid interactions with the dynamic linker).
Reviewed-by: Mark Brown broonie@kernel.org
On Wed, May 11, 2022 at 06:21:29PM +0100, Andre Przywara wrote:
The "bti" selftests are built with -nostdlib, which apparently automatically creates a statically linked binary, which is what we want and need for BTI (to avoid interactions with the dynamic linker).
However this is not true when building a PIE binary, which some toolchains (Ubuntu) configure as the default. When compiling btitest with such a toolchain, it will create a dynamically linked binary, which will probably fail some tests, as the dynamic linker might not support BTI: =================== TAP version 13 1..18 not ok 1 nohint_func/call_using_br_x0 not ok 2 nohint_func/call_using_br_x16 not ok 3 nohint_func/call_using_blr .... ===================
To make sure we create static binaries, add an explicit -static on the linker command line. This forces static linking even if the toolchain defaults to PIE builds, and fixes btitest runs on BTI enabled machines.
Signed-off-by: Andre Przywara andre.przywara@arm.com
Does this need to go in as a fix (cc stable, fixes tag)?
On Sun, 15 May 2022 11:05:23 +0100 Catalin Marinas catalin.marinas@arm.com wrote:
Hi,
On Wed, May 11, 2022 at 06:21:29PM +0100, Andre Przywara wrote:
The "bti" selftests are built with -nostdlib, which apparently automatically creates a statically linked binary, which is what we want and need for BTI (to avoid interactions with the dynamic linker).
However this is not true when building a PIE binary, which some toolchains (Ubuntu) configure as the default. When compiling btitest with such a toolchain, it will create a dynamically linked binary, which will probably fail some tests, as the dynamic linker might not support BTI: =================== TAP version 13 1..18 not ok 1 nohint_func/call_using_br_x0 not ok 2 nohint_func/call_using_br_x16 not ok 3 nohint_func/call_using_blr .... ===================
To make sure we create static binaries, add an explicit -static on the linker command line. This forces static linking even if the toolchain defaults to PIE builds, and fixes btitest runs on BTI enabled machines.
Signed-off-by: Andre Przywara andre.przywara@arm.com
Does this need to go in as a fix (cc stable, fixes tag)?
I dimly remember some discussion about stable fixes not being a real thing for the selftests? In any case:
Fixes: 314bcbf09f14 ("kselftest: arm64: Add BTI tests")
Cheers, Andre
On Mon, May 16, 2022 at 10:29:35AM +0100, Andre Przywara wrote:
On Sun, 15 May 2022 11:05:23 +0100 Catalin Marinas catalin.marinas@arm.com wrote:
On Wed, May 11, 2022 at 06:21:29PM +0100, Andre Przywara wrote:
The "bti" selftests are built with -nostdlib, which apparently automatically creates a statically linked binary, which is what we want and need for BTI (to avoid interactions with the dynamic linker).
However this is not true when building a PIE binary, which some toolchains (Ubuntu) configure as the default. When compiling btitest with such a toolchain, it will create a dynamically linked binary, which will probably fail some tests, as the dynamic linker might not support BTI: =================== TAP version 13 1..18 not ok 1 nohint_func/call_using_br_x0 not ok 2 nohint_func/call_using_br_x16 not ok 3 nohint_func/call_using_blr .... ===================
To make sure we create static binaries, add an explicit -static on the linker command line. This forces static linking even if the toolchain defaults to PIE builds, and fixes btitest runs on BTI enabled machines.
Signed-off-by: Andre Przywara andre.przywara@arm.com
Does this need to go in as a fix (cc stable, fixes tag)?
I dimly remember some discussion about stable fixes not being a real thing for the selftests? In any case:
Fixes: 314bcbf09f14 ("kselftest: arm64: Add BTI tests")
I'll add the fixes tag. I can see the occasional cc stable for kselftest patches.
On Wed, 11 May 2022 18:21:29 +0100, Andre Przywara wrote:
The "bti" selftests are built with -nostdlib, which apparently automatically creates a statically linked binary, which is what we want and need for BTI (to avoid interactions with the dynamic linker).
However this is not true when building a PIE binary, which some toolchains (Ubuntu) configure as the default. When compiling btitest with such a toolchain, it will create a dynamically linked binary, which will probably fail some tests, as the dynamic linker might not support BTI: =================== TAP version 13 1..18 not ok 1 nohint_func/call_using_br_x0 not ok 2 nohint_func/call_using_br_x16 not ok 3 nohint_func/call_using_blr .... ===================
[...]
Applied to arm64 (for-next/kselftest), thanks!
[1/1] kselftest/arm64: bti: force static linking https://git.kernel.org/arm64/c/d7a49291d786
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