Re: [PATCH v9 10/27] xsplice: Add helper elf routines

From: Konrad Rzeszutek Wilk <konrad@kernel.org>
To: Jan Beulich <JBeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>,
	andrew.cooper3@citrix.com,
	Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
	mpohlack@amazon.de, ross.lagerwall@citrix.com,
	sasha.levin@oracle.com, xen-devel@lists.xenproject.org
Subject: Re: [PATCH v9 10/27] xsplice: Add helper elf routines
Date: Wed, 27 Apr 2016 10:00:15 -0400	[thread overview]
Message-ID: <20160427140015.GC26384@x230.dumpdata.com> (raw)
In-Reply-To: <572085E902000078000E62CA@prv-mh.provo.novell.com>

On Wed, Apr 27, 2016 at 01:27:05AM -0600, Jan Beulich wrote:
> >>> On 27.04.16 at 03:59, <konrad.wilk@oracle.com> wrote:
> >> > +static int xsplice_header_check(const struct xsplice_elf *elf)
> >> > +{
> >> > +    const Elf_Ehdr *hdr = elf->hdr;
> >> > +
> >> > +    if ( sizeof(*elf->hdr) > elf->len )
> >> > +    {
> >> > +        dprintk(XENLOG_ERR, XSPLICE "%s: Section header is bigger than 
> > payload!\n",
> >> > +                elf->name);
> >> > +        return -EINVAL;
> >> > +    }
> >> > +
> >> > +    if ( !IS_ELF(*hdr) )
> >> > +    {
> >> > +        dprintk(XENLOG_ERR, XSPLICE "%s: Not an ELF payload!\n", elf->name);
> >> > +        return -EINVAL;
> >> > +    }
> >> > +
> >> > +    if ( hdr->e_ident[EI_CLASS] != ELFCLASS64 ||
> >> > +         hdr->e_ident[EI_DATA] != ELFDATA2LSB ||
> >> > +         hdr->e_ident[EI_OSABI] != ELFOSABI_SYSV ||
> >> 
> >> What about EI_VERSION and EI_ABIVERSION, btw?
> > 
> > As I did some prototype on ARM32 I realized that the EI_CLASS is wrong
> > in common code (as ELFCLASS32 is what ARM32 has). And the EI_ABIVERSION
> > too.
> 
> EI_CLASS I can easily see (and in fact EI_DATA would need to
> move there too, now that you menton this aspect), but why
> EI_ABIVERSION? Afaik there are no versions other than 0
> defined for ELFOSABI_NONE (which btw we wrongly call
> ELFOSABI_SYSV). That imo is either EI_OSABI and EI_ABIVERSION
> need to move, or both should be in common code.

I keep on getting messed up with the e_flags which for ARM32 has
0x500000:

 Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          0 (bytes into file)
  Start of section headers:          4528 (bytes into file)
  Flags:                             0x5000000, Version5 EABI
  Size of this header:               52 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           40 (bytes)
  Number of section headers:         33
  Section header string table index: 30

while same test-case under x86:
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x24
  Start of program headers:          0 (bytes into file)
  Start of section headers:          6680 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           64 (bytes)
  Number of section headers:         47
  Section header string table index: 44

Moved EI_ABIVERSION back in the common code. Moved EI_CLASS and EI_DATA
in platform specific.
> 
> Jan
> 

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