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Re: [Qemu-devel] [PATCH] linux-user: elfload: allocate and initialize me
From: |
Riku Voipio |
Subject: |
Re: [Qemu-devel] [PATCH] linux-user: elfload: allocate and initialize memsz-filesz gap |
Date: |
Thu, 13 Aug 2009 12:55:12 +0300 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
On Sun, Jul 12, 2009 at 03:02:38PM +0400, Max Filippov wrote:
> I'm having ppc ELF binaries that I'm running on x86 in linux-user emulation.
> Some of these binaries work fine, but others segfault.
> The latter binaries have segments with p_filesz < p_memsz and sections like
> .bss in this gap.
> Segfaults usually happen in attempt to access address within this gap.
> According to the linux-user/elfload.c only first p_filesz bytes of such
> segments are mmaped and mprotected.
> This patch mmaps p_memsz bytes and then zero out last p_memsz - p_filesz
> bytes of such segments.
> Is there a better way to do it?
After applying this patch, any arm-linux binaries on x86 fail run.
> Signed-off-by: Max Filippov <address@hidden>
> ---
> diff -burN qemu-snapshot-2009-07-11_r7249-orig/linux-user/elfload.c
> qemu-snapshot-2009-07-11_r7249/linux-user/elfload.c
> --- qemu-snapshot-2009-07-11_r7249-orig/linux-user/elfload.c 2009-07-11
> 06:12:23.000000000 +0400
> +++ qemu-snapshot-2009-07-11_r7249/linux-user/elfload.c 2009-07-12
> 04:47:47.000000000 +0400
> @@ -1380,7 +1380,7 @@
> }
>
> error = target_mmap(TARGET_ELF_PAGESTART(load_bias +
> elf_ppnt->p_vaddr),
> - (elf_ppnt->p_filesz +
> + (elf_ppnt->p_memsz +
> TARGET_ELF_PAGEOFFSET(elf_ppnt->p_vaddr)),
> elf_prot,
> (MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE),
> @@ -1392,6 +1392,20 @@
> exit(-1);
> }
>
> + if(elf_ppnt->p_memsz > elf_ppnt->p_filesz) {
> + abi_ulong pg = TARGET_ELF_PAGESTART(load_bias +
> elf_ppnt->p_vaddr) +
> + (elf_ppnt->p_filesz +
> + TARGET_ELF_PAGEOFFSET(elf_ppnt->p_vaddr));
> + abi_ulong sz = elf_ppnt->p_memsz - elf_ppnt->p_filesz;
> +
> + void *p = lock_user(PAGE_READ | PAGE_WRITE, pg, sz, 0);
> +
> + if (p) {
> + memset(p, 0, sz);
> + unlock_user(p, pg, sz);
> + }
> + }
> +
> #ifdef LOW_ELF_STACK
> if (TARGET_ELF_PAGESTART(elf_ppnt->p_vaddr) < elf_stack)
> elf_stack = TARGET_ELF_PAGESTART(elf_ppnt->p_vaddr);
>
>
> Thanks.
> -- Max
>
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