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Message-ID: <20150420211359.GS6817@brightrain.aerifal.cx>
Date: Mon, 20 Apr 2015 17:13:59 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: x86_64 and x32 fail to build
On Mon, Apr 20, 2015 at 10:21:31PM +0300, Alexander Monakov wrote:
> After recent commits musl fails to build for x86_64 and x32.
>
> When configuring on x86_64, configure mistakenly thinks the host compiler is
> going to produce code for x32. This is because __ILP32__ check wrongly
> succeeds. That is because it's looking for compilation failure due to #error
> preprocessor directive, but compilation instead fails because vis.h is not
> found (-include vis.h is added to CFLAGS with -I giving the path to it). I
> have used the following patch to proceed with the build:
>
> diff --git a/configure b/configure
> index 0e39694..cebee09 100755
> --- a/configure
> +++ b/configure
> @@ -440,7 +440,7 @@ printf "%s\n" "$visibility"
> fi
>
> if test "x$visibility" == xyes ; then
> -CFLAGS_AUTO="$CFLAGS_AUTO -include vis.h"
> +CFLAGS_AUTO="$CFLAGS_AUTO -I./arch/$ARCH -I src/internal -I./include -include vis.h"
This is probably inappropriate. I can think of two reasonable
alternatives; not sure which is better:
1. Have a global CFLAGS_PREDEF that that gets applied to all tests but
not added to CFLAGS_AUTO.
2. Just use -include src/internal/vis.h.
I kinda like #2 better.
> CFLAGS_AUTO="${CFLAGS_AUTO# }"
> fi
>
>
> Would be nice to rework trycppif configure function to be robust against this
> kind of failures.
>
> When targeting x32, build fails due to "jmp" instruction expecting a 64-bit
> argument. At least the following change is needed, but I'm not sure it's
> sufficient: the register should be zero-extended, not sign-extended:
>
> diff --git a/arch/x32/reloc.h b/arch/x32/reloc.h
> index 7c72d26..492fbf1 100644
> --- a/arch/x32/reloc.h
> +++ b/arch/x32/reloc.h
> @@ -23,4 +23,4 @@
> #define REL_TPOFF R_X86_64_TPOFF64
>
> #define CRTJMP(pc,sp) __asm__ __volatile__( \
> - "mov %1,%%esp ; jmp *%0" : : "r"(pc), "r"(sp) : "memory" )
> + "mov %1,%%esp ; jmp *%q0" : : "r"(pc), "r"(sp) : "memory" )
+ "mov %1,%%esp ; jmp *%0" : : "r"((uint64_t)(uintptr_t)pc), "r"(sp) : "memory" )
Rich
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