linux-kernel - Re: [PATCH] Use ELF_CORE_EFLAGS for kcore ELF header flags.

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Message-ID: <20080214090323.GA13450@edgar.se.axis.com>
Date:	Thu, 14 Feb 2008 10:03:23 +0100
From:	"Edgar E. Iglesias" <edgar.iglesias@...s.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Edgar E. Iglesias" <edgar.iglesias@...s.com>,
	ysato@...rs.sourceforge.jp, linux-kernel@...r.kernel.org,
	mikael.starvik@...s.com, Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH] Use ELF_CORE_EFLAGS for kcore ELF header flags.

On Wed, Feb 13, 2008 at 04:40:45PM -0800, Andrew Morton wrote:
> On Tue, 12 Feb 2008 14:34:23 +0100
> "Edgar E. Iglesias" <edgar.iglesias@...s.com> wrote:
> 
> > ELF_CORE_EFLAGS is already used by the binfmt_elf coredumper to set correct 
> > arch specific ELF header flags on coredumps. Use it for kcore aswell.
> > This corrects kcore files for the CRIS arch and I beleive it corrects 
> > ordinary coredumps for the H8/300.
> > 
> > Signed-off-by: Edgar E. Iglesias <edgar@...s.com>
> > 
> > ---
> > 
> > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> > index e78c81f..c2370c7 100644
> > --- a/fs/proc/kcore.c
> > +++ b/fs/proc/kcore.c
> > @@ -23,6 +23,10 @@
> >  
> >  #define CORE_STR "CORE"
> >  
> > +#ifndef ELF_CORE_EFLAGS
> > +#define ELF_CORE_EFLAGS	0
> > +#endif
> > +
> >  static int open_kcore(struct inode * inode, struct file * filp)
> >  {
> >  	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
> > @@ -164,11 +168,7 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
> >  	elf->e_entry	= 0;
> >  	elf->e_phoff	= sizeof(struct elfhdr);
> >  	elf->e_shoff	= 0;
> > -#if defined(CONFIG_H8300)
> > -	elf->e_flags	= ELF_FLAGS;
> > -#else
> > -	elf->e_flags	= 0;
> > -#endif
> > +	elf->e_flags	= ELF_CORE_EFLAGS;
> >  	elf->e_ehsize	= sizeof(struct elfhdr);
> >  	elf->e_phentsize= sizeof(struct elf_phdr);
> >  	elf->e_phnum	= nphdr;
> > diff --git a/include/asm-h8300/elf.h b/include/asm-h8300/elf.h
> > index 26bfc7e..806f20b 100644
> > --- a/include/asm-h8300/elf.h
> > +++ b/include/asm-h8300/elf.h
> > @@ -32,6 +32,8 @@ typedef unsigned long elf_fpregset_t;
> >  #define ELF_FLAGS       0x820000
> >  #endif
> >  
> > +#define ELF_CORE_EFLAGS ELF_FLAGS
> > +
> >  #define ELF_PLAT_INIT(_r)	_r->er1 = 0
> >  
> >  #define USE_ELF_CORE_DUMP
> 
> This will change behaviour on mips, which does
> 
> ./arch/mips/kernel/binfmt_elfn32.c:#define ELF_CORE_EFLAGS EF_MIPS_ABI2

IIUC, It will not change anything for MIPS. Please note that kcore.c was changed, not fs/binfmt_elf.c.
But I think the mips port should be defining ELF_CORE_EFLAGS in it's asm/elf.h to create kcore files that indicate the correct ABI for n32 kernels.

At the moment, I think a mips n32 kernel will dump cores for userspace programs with the correct EF_MIPS_ABI2 flag but the same kernel will create kcore files with zero eflags (o32).

Best regards
-- 
Edgar E. Iglesias
Axis Communications AB
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