linux-kernel - Re: [PATCH v5 7/8] vmcore: calculate vmcore file size from buffer size and total size of vmcore objects

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Date:	Tue, 14 May 2013 12:47:39 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	ebiederm@...ssion.com, akpm@...ux-foundation.org, cpw@....com,
	kumagai-atsushi@....nes.nec.co.jp, lisa.mitchell@...com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	zhangyanfei@...fujitsu.com, jingbai.ma@...com, linux-mm@...ck.org
Subject: Re: [PATCH v5 7/8] vmcore: calculate vmcore file size from buffer
 size and total size of vmcore objects

On Tue, May 14, 2013 at 10:57:46AM +0900, HATAYAMA Daisuke wrote:
> The previous patches newly added holes before each chunk of memory and
> the holes need to be count in vmcore file size. There are two ways to
> count file size in such a way:
> 
> 1) supporse p as a poitner to the last program header entry with
> PT_LOAD type, then roundup(p->p_offset + p->p_memsz, PAGE_SIZE), or
> 
> 2) calculate sum of size of buffers for ELF header, program headers,
> ELF note segments and objects in vmcore_list.
> 
> Although 1) is more direct and simpler than 2), 2) seems better in
> that it reflects internal object structure of /proc/vmcore. Thus, this
> patch changes get_vmcore_size_elf{64, 32} so that it calculates size
> in the way of 2).
> 
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
> ---

Looks good to me.

Acked-by: Vivek Goyal <vgoyal@...hat.com>

Vivek

> 
>  fs/proc/vmcore.c |   40 ++++++++++++++++++----------------------
>  1 files changed, 18 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index eb7ff29..ad6da17 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -210,36 +210,28 @@ static struct vmcore* __init get_new_element(void)
>  	return kzalloc(sizeof(struct vmcore), GFP_KERNEL);
>  }
>  
> -static u64 __init get_vmcore_size_elf64(char *elfptr, size_t elfsz)
> +static u64 __init get_vmcore_size_elf64(size_t elfsz, size_t elfnotesegsz,
> +					struct list_head *vc_list)
>  {
> -	int i;
>  	u64 size;
> -	Elf64_Ehdr *ehdr_ptr;
> -	Elf64_Phdr *phdr_ptr;
> +	struct vmcore *m;
>  
> -	ehdr_ptr = (Elf64_Ehdr *)elfptr;
> -	phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
> -	size = elfsz;
> -	for (i = 0; i < ehdr_ptr->e_phnum; i++) {
> -		size += phdr_ptr->p_memsz;
> -		phdr_ptr++;
> +	size = elfsz + elfnotesegsz;
> +	list_for_each_entry(m, vc_list, list) {
> +		size += m->size;
>  	}
>  	return size;
>  }
>  
> -static u64 __init get_vmcore_size_elf32(char *elfptr, size_t elfsz)
> +static u64 __init get_vmcore_size_elf32(size_t elfsz, size_t elfnotesegsz,
> +					struct list_head *vc_list)
>  {
> -	int i;
>  	u64 size;
> -	Elf32_Ehdr *ehdr_ptr;
> -	Elf32_Phdr *phdr_ptr;
> +	struct vmcore *m;
>  
> -	ehdr_ptr = (Elf32_Ehdr *)elfptr;
> -	phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
> -	size = elfsz;
> -	for (i = 0; i < ehdr_ptr->e_phnum; i++) {
> -		size += phdr_ptr->p_memsz;
> -		phdr_ptr++;
> +	size = elfsz + elfnotesegsz;
> +	list_for_each_entry(m, vc_list, list) {
> +		size += m->size;
>  	}
>  	return size;
>  }
> @@ -755,14 +747,18 @@ static int __init parse_crash_elf_headers(void)
>  			return rc;
>  
>  		/* Determine vmcore size. */
> -		vmcore_size = get_vmcore_size_elf64(elfcorebuf, elfcorebuf_sz);
> +		vmcore_size = get_vmcore_size_elf64(elfcorebuf_sz,
> +						    elfnotesegbuf_sz,
> +						    &vmcore_list);
>  	} else if (e_ident[EI_CLASS] == ELFCLASS32) {
>  		rc = parse_crash_elf32_headers();
>  		if (rc)
>  			return rc;
>  
>  		/* Determine vmcore size. */
> -		vmcore_size = get_vmcore_size_elf32(elfcorebuf, elfcorebuf_sz);
> +		vmcore_size = get_vmcore_size_elf32(elfcorebuf_sz,
> +						    elfnotesegbuf_sz,
> +						    &vmcore_list);
>  	} else {
>  		pr_warn("Warning: Core image elf header is not sane\n");
>  		return -EINVAL;
--
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