From: Michael Ellerman <mpe@ellerman.id.au>
To: Clement Courbet <courbet@google.com>
Cc: Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@alien8.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
Ingo Molnar <mingo@redhat.com>, Paul Mackerras <paulus@samba.org>,
Clement Courbet <courbet@google.com>,
"H. Peter Anvin" <hpa@zytor.com>, Joe Perches <joe@perches.com>,
Bernd Petrovitsch <bernd@petrovitsch.priv.at>,
Nathan Chancellor <natechancellor@gmail.com>,
linuxppc-dev@lists.ozlabs.org,
Thomas Gleixner <tglx@linutronix.de>,
Allison Randal <allison@lohutok.net>
Subject: Re: [PATCH] x86: Alias memset to __builtin_memset.
Date: Fri, 27 Mar 2020 15:06:14 +1100 [thread overview]
Message-ID: <87a742wifd.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20200326123841.134068-1-courbet@google.com>
Clement Courbet <courbet@google.com> writes:
> I discussed with the original authors who added freestanding to our
> build. It turns out that it was added globally but this was just to
> to workaround powerpc not compiling under clang, but they felt the
> fix was appropriate globally.
>
> Now Nick has dug up https://lkml.org/lkml/2019/8/29/1300, which
> advises against freestanding. Also, I've did some research and
> discovered that the original reason for using freestanding for
> powerpc has been fixed here:
> https://lore.kernel.org/linuxppc-dev/20191119045712.39633-3-natechancellor@gmail.com/
>
> I'm going to remove -ffreestanding from downstream, so we don't really need
> this anymore, sorry for waisting people's time.
>
> I wonder if the freestanding fix from the aforementioned patch is really needed
> though. I think that clang is actually right to point out the issue.
> I don't see any reason why setjmp()/longjmp() are declared as taking longs
> rather than ints. The implementation looks like it only ever propagates the
> value (in longjmp) or sets it to 1 (in setjmp), and we only ever call longjmp
> with integer parameters. But I'm not a PowerPC expert, so I might
> be misreading the code.
>
>
> So it seems that we could just remove freestanding altogether and rewrite the
> code to:
>
> diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> index 279d03a1eec6..7941ae68fe21 100644
> --- a/arch/powerpc/include/asm/setjmp.h
> +++ b/arch/powerpc/include/asm/setjmp.h
> @@ -12,7 +12,9 @@
>
> #define JMP_BUF_LEN 23
> -extern long setjmp(long *);
> -extern void longjmp(long *, long);
> +typedef long * jmp_buf;
> +
> +extern int setjmp(jmp_buf);
> +extern void longjmp(jmp_buf, int);
>
> I'm happy to send a patch for this, and get rid of more -ffreestanding.
> Opinions ?
If it works then it looks like a much better fix than using -ffreestanding.
Please submit a patch with a change log etc. and I'd be happy to merge
it.
cheers
next prev parent reply other threads:[~2020-03-27 4:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200323114207.222412-1-courbet@google.com>
2020-03-26 12:38 ` [PATCH] x86: Alias memset to __builtin_memset Clement Courbet
2020-03-26 17:18 ` Nick Desaulniers
2020-03-27 4:06 ` Michael Ellerman [this message]
2020-03-27 17:12 ` Segher Boessenkool
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