linux-kernel - Re: [PATCH v4 2/2] mips: Differentiate between 32 and 64 bit ELF header

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Message-ID: <20160211104903.GD11091@linux-mips.org>
Date:	Thu, 11 Feb 2016 11:49:03 +0100
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	Daniel Wagner <daniel.wagner@...-carit.de>
Cc:	"Maciej W. Rozycki" <macro@...tec.com>,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org
Subject: Re: [PATCH v4 2/2] mips: Differentiate between 32 and 64 bit ELF
 header

On Wed, Feb 10, 2016 at 10:21:21AM +0100, Daniel Wagner wrote:

> Depending on the configuration either the 32 or 64 bit version of
> elf_check_arch() is defined. parse_crash_elf{32|64}_headers() does
> some basic verification of the ELF header via
> vmcore_elf{32|64}_check_arch() which happen to map to elf_check_arch().
> Since the implementation 32 and 64 bit version of elf_check_arch()
> differ, we use the wrong type:
> 
>    In file included from include/linux/elf.h:4:0,
>                     from fs/proc/vmcore.c:13:
>    fs/proc/vmcore.c: In function 'parse_crash_elf64_headers':
> >> arch/mips/include/asm/elf.h:228:23: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
>      struct elfhdr *__h = (hdr);     \
>                           ^
>    include/linux/crash_dump.h:41:37: note: in expansion of macro 'elf_check_arch'
>     #define vmcore_elf64_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x))
>                                         ^
>    fs/proc/vmcore.c:1015:4: note: in expansion of macro 'vmcore_elf64_check_arch'
>       !vmcore_elf64_check_arch(&ehdr) ||
>        ^
> 
> Therefore, we rather define vmcore_elf{32|64}_check_arch() as a
> basic machine check and use it also in binfm_elf?32.c as well.
> 
> Signed-off-by: Daniel Wagner <daniel.wagner@...-carit.de>
> Suggested-by: Maciej W. Rozycki <macro@...tec.com>
> Reviewed-by: Maciej W. Rozycki <macro@...tec.com>
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>

Thanks, applied.

I'm getting a less spectacular warning from gcc 5.2:

  CC      fs/proc/vmcore.o
fs/proc/vmcore.c: In function ‘parse_crash_elf64_headers’:
fs/proc/vmcore.c:939:47: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]

  Ralf