Re: [PATCH v3] powerpc: Make setjmp/longjmp signature standard

From: Nick Desaulniers <ndesaulniers@google.com>
To: Clement Courbet <courbet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"# 3.4.x" <stable@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Paul Mackerras <paulus@samba.org>,
	Nathan Chancellor <natechancellor@gmail.com>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3] powerpc: Make setjmp/longjmp signature standard
Date: Mon, 30 Mar 2020 09:20:47 -0700	[thread overview]
Message-ID: <CAKwvOdmO_0yosb-k+UHenSa5W5HtZgPLFaHfapxD8WiDNpFJUA@mail.gmail.com> (raw)
In-Reply-To: <20200330080400.124803-1-courbet@google.com>

On Mon, Mar 30, 2020 at 1:04 AM Clement Courbet <courbet@google.com> wrote:
>
> Declaring setjmp()/longjmp() as taking longs makes the signature
> non-standard, and makes clang complain. In the past, this has been
> worked around by adding -ffreestanding to the compile flags.
>
> The implementation looks like it only ever propagates the value
> (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> with integer parameters.
>
> This allows removing -ffreestanding from the compilation flags.
>
> Context:
> https://lore.kernel.org/patchwork/patch/1214060
> https://lore.kernel.org/patchwork/patch/1216174
>
> Signed-off-by: Clement Courbet <courbet@google.com>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> Tested-by: Nathan Chancellor <natechancellor@gmail.com>
> Cc: stable@vger.kernel.org # v4.14+
> Fixes: c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")

Third time's a charm (for patches that tackle this warning). Thanks
for following up on this cleanup!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

The extent of my testing was compile testing with Clang.

>
> ---
>
> v2:
> Use and array type as suggested by Segher Boessenkool
> Add fix tags.
>
> v3:
> Properly place tags.
> ---
>  arch/powerpc/include/asm/setjmp.h | 6 ++++--
>  arch/powerpc/kexec/Makefile       | 3 ---
>  arch/powerpc/xmon/Makefile        | 3 ---
>  3 files changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> index e9f81bb3f83b..f798e80e4106 100644
> --- a/arch/powerpc/include/asm/setjmp.h
> +++ b/arch/powerpc/include/asm/setjmp.h
> @@ -7,7 +7,9 @@
>
>  #define JMP_BUF_LEN    23
>
> -extern long setjmp(long *) __attribute__((returns_twice));
> -extern void longjmp(long *, long) __attribute__((noreturn));
> +typedef long jmp_buf[JMP_BUF_LEN];
> +
> +extern int setjmp(jmp_buf env) __attribute__((returns_twice));
> +extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));
>
>  #endif /* _ASM_POWERPC_SETJMP_H */
> diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
> index 378f6108a414..86380c69f5ce 100644
> --- a/arch/powerpc/kexec/Makefile
> +++ b/arch/powerpc/kexec/Makefile
> @@ -3,9 +3,6 @@
>  # Makefile for the linux kernel.
>  #
>
> -# Avoid clang warnings around longjmp/setjmp declarations
> -CFLAGS_crash.o += -ffreestanding
> -
>  obj-y                          += core.o crash.o core_$(BITS).o
>
>  obj-$(CONFIG_PPC32)            += relocate_32.o
> diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
> index c3842dbeb1b7..6f9cccea54f3 100644
> --- a/arch/powerpc/xmon/Makefile
> +++ b/arch/powerpc/xmon/Makefile
> @@ -1,9 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  # Makefile for xmon
>
> -# Avoid clang warnings around longjmp/setjmp declarations
> -subdir-ccflags-y := -ffreestanding
> -
>  GCOV_PROFILE := n
>  KCOV_INSTRUMENT := n
>  UBSAN_SANITIZE := n
> --
> 2.26.0.rc2.310.g2932bb562d-goog
>

-- 
Thanks,
~Nick Desaulniers