linux-kernel - Re: [PATCH v1] powerpc: Make setjmp/longjump signature standard

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Date:   Fri, 27 Mar 2020 18:45:21 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Clement Courbet <courbet@...gle.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH v1] powerpc: Make setjmp/longjump signature standard

Subject line, change longjump to longjmp

Le 27/03/2020 à 11:07, Clement Courbet a écrit :
> 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@...gle.com>
> ---
>   arch/powerpc/include/asm/setjmp.h | 6 ++++--
>   arch/powerpc/kexec/Makefile       | 3 ---
>   2 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> index e9f81bb3f83b..84bb0d140d59 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;

Do we need that new opaque typedef ? Why not just keep long * ?

> +
> +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
> 

Christophe