From: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
To: vgoyal@redhat.com
Cc: ebiederm@xmission.com, cpw@sgi.com,
kumagai-atsushi@mxc.nes.nec.co.jp, lisa.mitchell@hp.com,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/13] vmcore: round up buffer size of ELF headers by PAGE_SIZE
Date: Tue, 19 Feb 2013 00:58:56 +0900 (JST) [thread overview]
Message-ID: <20130219.005856.267479651.d.hatayama@jp.fujitsu.com> (raw)
In-Reply-To: <20130215151821.GB27784@redhat.com>
From: Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH 02/13] vmcore: round up buffer size of ELF headers by PAGE_SIZE
Date: Fri, 15 Feb 2013 10:18:21 -0500
> On Thu, Feb 14, 2013 at 07:11:54PM +0900, HATAYAMA Daisuke wrote:
>> To satisfy mmap() page-size boundary requirement, reound up buffer
>> size of ELF headers by PAGE_SIZE. The resulting value becomes offset
>> of ELF 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.
>>
>> Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
>> ---
>>
>> fs/proc/vmcore.c | 9 +++++----
>> 1 files changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
>> index 85714c3..5010ead 100644
>> --- a/fs/proc/vmcore.c
>> +++ b/fs/proc/vmcore.c
>> @@ -313,7 +313,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
>> phdr.p_flags = 0;
>> note_off = sizeof(Elf64_Ehdr) +
>> (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;
>> @@ -331,6 +331,8 @@ 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;
>>
>
> Hi Hatayama,
>
> While reading the /proc/vmcore code again, I realized that we are making
> a horrible assumption. And that is that all PT_NOTE program headers
> prepared by kexec-tools are contiguous. And we also seem to be assuming
> that all PT_NOTE phdrs are following immediately Elf Header.
>
> /* Add merged PT_NOTE program header*/
> tmp = elfptr + sizeof(Elf64_Ehdr);
> memcpy(tmp, &phdr, sizeof(phdr));
> tmp += sizeof(phdr);
>
> /* Remove unwanted PT_NOTE program headers. */
> i = (nr_ptnote - 1) * sizeof(Elf64_Phdr);
> *elfsz = *elfsz - i;
> memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr)));
>
> I know I wrote this code but now I realize that this is very bad
> assumption. We should not be assuming where PT_NOTE headers are and
> also should not be assuming that these are contiguous.
>
> This will require fixing. I think we just need to read old elf headers
> in a buffer and prepare new headers (merged one) in a separate buffer
> instead of trying to make do with single buffer.
>
> If it is not too much of trouble, can you please do this cleanup and
> rebase your patches on top of it.
>
> Thanks
> Vivek
Yes, I'll do this.
Thanks.
HATAYAMA, Daisuke
next prev parent reply other threads:[~2013-02-18 15:59 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-14 10:11 [PATCH 00/13] kdump, vmcore: support mmap() on /proc/vmcore HATAYAMA Daisuke
2013-02-14 10:11 ` [PATCH 01/13] vmcore: allocate buffer for ELF headers on page-size alignment HATAYAMA Daisuke
2013-02-15 15:01 ` Vivek Goyal
2013-02-14 10:11 ` [PATCH 02/13] vmcore: round up buffer size of ELF headers by PAGE_SIZE HATAYAMA Daisuke
2013-02-15 15:18 ` Vivek Goyal
2013-02-18 15:58 ` HATAYAMA Daisuke [this message]
2013-02-14 10:11 ` [PATCH 03/13] vmcore: fill unused part of buffer for ELF headers with 0 HATAYAMA Daisuke
2013-02-14 10:12 ` [PATCH 04/13] vmcore: introduce types for objects copied in 2nd kernel HATAYAMA Daisuke
2013-02-15 15:28 ` Vivek Goyal
2013-02-18 16:06 ` HATAYAMA Daisuke
2013-02-19 23:07 ` Vivek Goyal
2013-02-14 10:12 ` [PATCH 05/13] vmcore: modify ELF32 code according to new type HATAYAMA Daisuke
2013-02-15 15:30 ` Vivek Goyal
2013-02-18 16:11 ` HATAYAMA Daisuke
2013-02-14 10:12 ` [PATCH 06/13] vmcore: modify vmcore clean-up function to free buffer on 2nd kernel HATAYAMA Daisuke
2013-02-15 15:32 ` Vivek Goyal
2013-02-14 10:12 ` [PATCH 07/13] vmcore: modify read_vmcore() to read " HATAYAMA Daisuke
2013-02-15 15:51 ` Vivek Goyal
2013-02-14 10:12 ` [PATCH 08/13] vmcore: remove unused helper function HATAYAMA Daisuke
2013-02-15 15:52 ` Vivek Goyal
2013-02-14 10:12 ` [PATCH 09/13] vmcore: copy ELF note segments in buffer on 2nd kernel HATAYAMA Daisuke
2013-02-15 16:53 ` Vivek Goyal
2013-02-18 17:02 ` HATAYAMA Daisuke
2013-02-19 23:05 ` Vivek Goyal
2013-02-14 10:12 ` [PATCH 10/13] vmcore: round-up offset of vmcore object in page-size boundary HATAYAMA Daisuke
2013-02-14 10:12 ` [PATCH 11/13] vmcore: count holes generated by round-up operation for vmcore size HATAYAMA Daisuke
2013-02-14 10:12 ` [PATCH 12/13] vmcore: copy non page-size aligned head and tail pages in 2nd kernel HATAYAMA Daisuke
2013-02-14 10:12 ` [PATCH 13/13] vmcore: introduce mmap_vmcore() HATAYAMA Daisuke
2013-02-15 3:57 ` [PATCH 00/13] kdump, vmcore: support mmap() on /proc/vmcore Atsushi Kumagai
2013-02-18 0:16 ` Hatayama, Daisuke
2013-03-27 5:51 ` makedumpfile mmap() benchmark Jingbai Ma
2013-03-27 6:23 ` HATAYAMA Daisuke
2013-03-27 6:35 ` Jingbai Ma
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