linux-kernel - Re: [patch] Fix vdso32 relocation for paddr

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Date:	Fri, 28 Aug 2009 17:13:29 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Jan Kratochvil <jan.kratochvil@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>
Subject: Re: [patch] Fix vdso32 relocation for paddr

On Thu, Aug 27, 2009 at 6:31 AM, Jan
Kratochvil<jan.kratochvil@...hat.com> wrote:
> Hi,
>
> `readelf -Wl file-dumped-from-/proc/self/maps-[vdso]' for x86_64 process prints:
> Program Headers:
>  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
>  LOAD           0x000000 0xffffffffff700000 0xffffffffff700000 0x000890 0x000890 R E 0x1000
>  DYNAMIC        0x000410 0xffffffffff700410 0xffffffffff700410 0x0000f0 0x0000f0 R   0x8
>  NOTE           0x0002d0 0xffffffffff7002d0 0xffffffffff7002d0 0x00003c 0x00003c R   0x4
>  GNU_EH_FRAME   0x00030c 0xffffffffff70030c 0xffffffffff70030c 0x000034 0x000034 R   0x4
>
> while such dump for i386 process prints:
> Program Headers:
>  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
>  LOAD           0x000000 0xffffe000 0x00000000 0x00434 0x00434 R E 0x1000
>  DYNAMIC        0x000350 0xffffe350 0x00000350 0x00078 0x00078 R   0x4
>  NOTE           0x0001c4 0xffffe1c4 0x000001c4 0x00060 0x00060 R   0x4
>  GNU_EH_FRAME   0x000224 0xffffe224 0x00000224 0x00024 0x00024 R   0x4
>
> The mapped location can be arbirary (according to the rules of PIC - Position
> Independent Code) but currently the i386 vdso (vdso32) looks as an overlayed
> code as it has LMA != VMA (rule contained in GDB function section_is_overlay,
> as suggested by Daniel Jacobowitz).
>
> Fixed vdso32 prints:
> Program Headers:
>  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
>  LOAD           0x000000 0xffffe000 0xffffe000 0x00434 0x00434 R E 0x1000
>  DYNAMIC        0x000350 0xffffe350 0xffffe350 0x00078 0x00078 R   0x4
>  NOTE           0x0001c4 0xffffe1c4 0xffffe1c4 0x00060 0x00060 R   0x4
>  GNU_EH_FRAME   0x000224 0xffffe224 0xffffe224 0x00024 0x00024 R   0x4
>
> It required now a workaround in GDB patch so at least to fix it in Linux kernel:
>        http://sourceware.org/ml/gdb-patches/2009-08/msg00437.html
>
>

Reviewed-by: WANG Cong <xiyou.wangcong@...il.com>

This patch looks fine for me. But I think we should hear from Roland.
Roland?


> Thanks,
> Jan
>
>
> Signed-off-by: Jan Kratochvil <jan.kratochvil@...hat.com>
>
> --- linux-2.6.30.x86_64/arch/x86/vdso/vdso32-setup.c-orig       2009-08-26 22:23:08.000000000 +0200
> +++ linux-2.6.30.x86_64/arch/x86/vdso/vdso32-setup.c    2009-08-26 22:38:10.000000000 +0200
> @@ -172,6 +172,7 @@ static __init void relocate_vdso(Elf32_E
>        phdr = (void *)ehdr + ehdr->e_phoff;
>        for (i = 0; i < ehdr->e_phnum; i++) {
>                phdr[i].p_vaddr += VDSO_ADDR_ADJUST;
> +               phdr[i].p_paddr += VDSO_ADDR_ADJUST;
>
>                /* relocate dynamic stuff */
>                if (phdr[i].p_type == PT_DYNAMIC)
> --
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