linux-kernel - Re: [PATCH v2 05/20] vmcore: round up buffer size of ELF headers by PAGE

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Date:	Wed, 6 Mar 2013 23:51:55 +0800
From:	Yanfei Zhang <zhangyanfei.yes@...il.com>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	vgoyal@...hat.com, ebiederm@...ssion.com, cpw@....com,
	kumagai-atsushi@....nes.nec.co.jp, lisa.mitchell@...com,
	heiko.carstens@...ibm.com, akpm@...ux-foundation.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/20] vmcore: round up buffer size of ELF headers by PAGE_SIZE

2013/3/2 HATAYAMA Daisuke <d.hatayama@...fujitsu.com>:
> To satisfy mmap() page-size boundary requirement, round up buffer size
> of ELF headers by PAGE_SIZE. The resulting value becomes offset of ELF
      ~~~~~~~~~~~
      ELF header? or ELF program headers?

> note segments and it's assigned in unique PT_NOTE program header
> entry.
>
> Also, some part that assumes past ELF headers' size is replaced by
> this new rounded-up value.

Reviewed-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>

>
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
> ---
>
>  fs/proc/vmcore.c |   16 ++++++++--------
>  1 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 1b02d01..c511cf4 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -340,7 +340,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
>         phdr.p_flags   = 0;
>         note_off = ehdr_ptr->e_phoff +
>                         (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf64_Phdr);
> -       phdr.p_offset  = note_off;
> +       phdr.p_offset  = roundup(note_off, PAGE_SIZE);
>         phdr.p_vaddr   = phdr.p_paddr = 0;
>         phdr.p_filesz  = phdr.p_memsz = phdr_sz;
>         phdr.p_align   = 0;
> @@ -353,6 +353,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
>         /* Modify e_phnum to reflect merged headers. */
>         ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
>
> +       *elfsz = roundup(*elfsz, PAGE_SIZE);
>  out:
>         return 0;
>  }
> @@ -449,7 +450,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
>         phdr.p_flags   = 0;
>         note_off = ehdr_ptr->e_phoff +
>                         (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf32_Phdr);
> -       phdr.p_offset  = note_off;
> +       phdr.p_offset  = roundup(note_off, PAGE_SIZE);
>         phdr.p_vaddr   = phdr.p_paddr = 0;
>         phdr.p_filesz  = phdr.p_memsz = phdr_sz;
>         phdr.p_align   = 0;
> @@ -462,6 +463,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
>         /* Modify e_phnum to reflect merged headers. */
>         ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
>
> +       *elfsz = roundup(*elfsz, PAGE_SIZE);
>  out:
>         return 0;
>  }
> @@ -482,9 +484,8 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
>         phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */
>
>         /* First program header is PT_NOTE header. */
> -       vmcore_off = ehdr_ptr->e_phoff +
> -                       (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr) +
> -                       phdr_ptr->p_memsz; /* Note sections */
> +       vmcore_off = phdr_ptr->p_offset + roundup(phdr_ptr->p_memsz,
> +                                                 PAGE_SIZE);
>
>         for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
>                 if (phdr_ptr->p_type != PT_LOAD)
> @@ -519,9 +520,8 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
>         phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */
>
>         /* First program header is PT_NOTE header. */
> -       vmcore_off = ehdr_ptr->e_phoff +
> -                       (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr) +
> -                       phdr_ptr->p_memsz; /* Note sections */
> +       vmcore_off = phdr_ptr->p_offset + roundup(phdr_ptr->p_memsz,
> +                                                PAGE_SIZE);
>
>         for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
>                 if (phdr_ptr->p_type != PT_LOAD)
>
> --
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