Re: [PATCH] selftests: sigaltstack: fix -Wuninitialized

[Naresh Kamboju]

On Thu, 9 Mar 2023 at 01:29, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:
>
> Building sigaltstack with clang via:
> $ ARCH=x86 make LLVM=1 -C tools/testing/selftests/sigaltstack/
>
> produces the following warning:
>   warning: variable 'sp' is uninitialized when used here [-Wuninitialized]
>   if (sp < (unsigned long)sstack ||
>       ^~
>
> Clang expects these to be declared at global scope; we've fixed this in
> the kernel proper by using the macro `current_stack_pointer`. This is
> defined in different headers for different target architectures, so just
> create a new header that defines the arch-specific register names for
> the stack pointer register, and define it for more targets (at least the
> ones that support current_stack_pointer/ARCH_HAS_CURRENT_STACK_POINTER).
>
> Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> Link: https://lore.kernel.org/lkml/CA+G9fYsi3OOu7yCsMutpzKDnBMAzJBCPimBp86LhGBa0eCnEpA@xxxxxxxxxxxxxx/
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

Build and boot tested with clang-16 and tested sigaltstack
on arm64, armv7, FVP, x86_64 and i386 [1] & [2].
These tests were performed at Linaro test farm by Anders
with the help of tuxplan / tuxmake and tuxrun.

Tested-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
Tested-by:  Anders Roxell <anders.roxell@xxxxxxxxxx>


Build log:
-------
clang --target=aarch64-linux-gnu -fintegrated-as
-Werror=unknown-warning-option -Werror=ignored-optimization-argument
-Werror=option-ignored -Werror=unused-command-line-argument
--target=aarch64-linux-gnu -fintegrated-as -Wall     sas.c  -o
/home/tuxbuild/.cache/tuxmake/builds/1/build/kselftest/sigaltstack/sas

Test log:
----------

Linux version 6.3.0-rc1-next-20230310 (tuxmake@tuxmake) (Debian clang
version 16.0.0 (++20230228093516+60692a66ced6-1~exp1~20230228093525.41),
Debian LLD 16.0.0) #1 SMP PREEMPT @1678519789
...

[   56.327569] kselftest: Running tests in sigaltstack
TAP version 13
1..1
# selftests: sigaltstack: sas
# # [NOTE] the stack size is 26400
# TAP version 13
# 1..3
# ok 1 Initial sigaltstack state was SS_DISABLE
# # [RUN] signal USR1
# ok 2 sigaltstack is disabled in sighandler
# # [RUN] switched to user ctx
# # [RUN] signal USR2
# # [OK] Stack preserved
# ok 3 sigaltstack is still SS_AUTODISARM after signal
# # Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0
ok 1 selftests: sigaltstack: sas

Details of test log links provided [3].

> ---
> Cc: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Cc: KERNEL SELFTEST FRAMEWORK <linux-kselftest@xxxxxxxxxxxxxxx>
> Cc: linux-api@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: lkft-triage@xxxxxxxxxxxxxxxx
> Cc: Shuah Khan <shuah@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: "Chang S. Bae" <chang.seok.bae@xxxxxxxxx>
> Cc: Len Brown <len.brown@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Stas Sergeev <stsp@xxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Anders Roxell <anders.roxell@xxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> Cc: llvm@xxxxxxxxxxxxxxx
> ---
>  .../sigaltstack/current_stack_pointer.h       | 23 +++++++++++++++++++
>  tools/testing/selftests/sigaltstack/sas.c     |  7 +-----
>  2 files changed, 24 insertions(+), 6 deletions(-)
>  create mode 100644 tools/testing/selftests/sigaltstack/current_stack_pointer.h
>
> diff --git a/tools/testing/selftests/sigaltstack/current_stack_pointer.h b/tools/testing/selftests/sigaltstack/current_stack_pointer.h
> new file mode 100644
> index 000000000000..ea9bdf3a90b1
> --- /dev/null
> +++ b/tools/testing/selftests/sigaltstack/current_stack_pointer.h
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#if __alpha__
> +register unsigned long sp asm("$30");
> +#elif __arm__ || __aarch64__ || __csky__ || __m68k__ || __mips__ || __riscv
> +register unsigned long sp asm("sp");
> +#elif __i386__
> +register unsigned long sp asm("esp");
> +#elif __loongarch64
> +register unsigned long sp asm("$sp");
> +#elif __ppc__
> +register unsigned long sp asm("r1");
> +#elif __s390x__
> +register unsigned long sp asm("%15");
> +#elif __sh__
> +register unsigned long sp asm("r15");
> +#elif __x86_64__
> +register unsigned long sp asm("rsp");
> +#elif __XTENSA__
> +register unsigned long sp asm("a1");
> +#else
> +#error "implement current_stack_pointer equivalent"
> +#endif
> diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
> index c53b070755b6..98d37cb744fb 100644
> --- a/tools/testing/selftests/sigaltstack/sas.c
> +++ b/tools/testing/selftests/sigaltstack/sas.c
> @@ -20,6 +20,7 @@
>  #include <sys/auxv.h>
>
>  #include "../kselftest.h"
> +#include "current_stack_pointer.h"
>
>  #ifndef SS_AUTODISARM
>  #define SS_AUTODISARM  (1U << 31)
> @@ -46,12 +47,6 @@ void my_usr1(int sig, siginfo_t *si, void *u)
>         stack_t stk;
>         struct stk_data *p;
>
> -#if __s390x__
> -       register unsigned long sp asm("%15");
> -#else
> -       register unsigned long sp asm("sp");
> -#endif
> -
>         if (sp < (unsigned long)sstack ||
>                         sp >= (unsigned long)sstack + stack_size) {
>                 ksft_exit_fail_msg("SP is not on sigaltstack\n");
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog

log link:
-----
[1] https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/lore_kernel_org_linux-kselftest_20230308195933_806917-1-ndesaulniers_google_com/?failures_only=false#!?filter-tests=kselftest-sigaltstack&details=#test-results
[2] https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/lore_kernel_org_linux-kselftest_20230308195933_806917-1-ndesaulniers_google_com/testrun/15468761/suite/kselftest-sigaltstack/test/sigaltstack_sas/log
[3] https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/anders/tests/2MrJ2e4bDCC4iZjIrnRqmnE7KfC


--
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https://lkft.linaro.org