Re: [PATCH v2 04/20] vmcore: allocate buffer for ELF headers on page-sizealignment

[Zhang Yanfei]

ä 2013å03æ02æ 16:36, HATAYAMA Daisuke åé:
> Allocate buffer for ELF headers on page-size aligned boudary to
> satisfy mmap() requirement. For this, __get_free_pages() is used
> instead of kmalloc().
> 
> Also, later patch will decrease actually used buffer size for ELF
> headers, so it's necessary to keep original buffer size and actually
> used buffer size separately. elfcorebuf_sz_orig keeps the original one
> and elfcorebuf_sz the actually used one.
> 
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
> ---
> 
>  fs/proc/vmcore.c |   30 +++++++++++++++++++++---------
>  1 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index b5c9e33..1b02d01 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -31,6 +31,7 @@ static LIST_HEAD(vmcore_list);
>  /* Stores the pointer to the buffer containing kernel elf core headers. */
>  static char *elfcorebuf;
>  static size_t elfcorebuf_sz;
> +static size_t elfcorebuf_sz_orig;
>  
>  /* Total size of vmcore file. */
>  static u64 vmcore_size;
> @@ -610,26 +611,31 @@ static int __init parse_crash_elf64_headers(void)
>  
>  	/* Read in all elf headers. */
>  	elfcorebuf_sz = ehdr.e_phoff + ehdr.e_phnum * sizeof(Elf64_Phdr);
> -	elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
> +	elfcorebuf_sz_orig = elfcorebuf_sz;
> +	elfcorebuf = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
> +					       get_order(elfcorebuf_sz_orig));
>  	if (!elfcorebuf)
>  		return -ENOMEM;
>  	addr = elfcorehdr_addr;
>  	rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0);
>  	if (rc < 0) {
> -		kfree(elfcorebuf);
> +		free_pages((unsigned long)elfcorebuf,
> +			   get_order(elfcorebuf_sz_orig));
>  		return rc;
>  	}
>  
>  	/* Merge all PT_NOTE headers into one. */
>  	rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
>  	if (rc) {
> -		kfree(elfcorebuf);
> +		free_pages((unsigned long)elfcorebuf,
> +			   get_order(elfcorebuf_sz_orig));
>  		return rc;
>  	}
>  	rc = process_ptload_program_headers_elf64(elfcorebuf, elfcorebuf_sz,
>  							&vmcore_list);
>  	if (rc) {
> -		kfree(elfcorebuf);
> +		free_pages((unsigned long)elfcorebuf,
> +			   get_order(elfcorebuf_sz_orig));
>  		return rc;
>  	}
>  	set_vmcore_list_offsets_elf64(elfcorebuf, &vmcore_list);
> @@ -665,26 +671,31 @@ static int __init parse_crash_elf32_headers(void)
>  
>  	/* Read in all elf headers. */
>  	elfcorebuf_sz = ehdr.e_phoff + ehdr.e_phnum * sizeof(Elf32_Phdr);
> -	elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
> +	elfcorebuf_sz_orig = elfcorebuf_sz;
> +	elfcorebuf = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
> +					       get_order(elfcorebuf_sz));

Why not elfcorebuf_sz_orig here?

>  	if (!elfcorebuf)
>  		return -ENOMEM;
>  	addr = elfcorehdr_addr;
>  	rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0);
>  	if (rc < 0) {
> -		kfree(elfcorebuf);
> +		free_pages((unsigned long)elfcorebuf,
> +			   get_order(elfcorebuf_sz_orig));
>  		return rc;
>  	}
>  
>  	/* Merge all PT_NOTE headers into one. */
>  	rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
>  	if (rc) {
> -		kfree(elfcorebuf);
> +		free_pages((unsigned long)elfcorebuf,
> +			   get_order(elfcorebuf_sz_orig));
>  		return rc;
>  	}
>  	rc = process_ptload_program_headers_elf32(elfcorebuf, elfcorebuf_sz,
>  								&vmcore_list);
>  	if (rc) {
> -		kfree(elfcorebuf);
> +		free_pages((unsigned long)elfcorebuf,
> +			   get_order(elfcorebuf_sz_orig));
>  		return rc;
>  	}
>  	set_vmcore_list_offsets_elf32(elfcorebuf, &vmcore_list);
> @@ -766,7 +777,8 @@ void vmcore_cleanup(void)
>  		list_del(&m->list);
>  		kfree(m);
>  	}
> -	kfree(elfcorebuf);
> +	free_pages((unsigned long)elfcorebuf,
> +		   get_order(elfcorebuf_sz_orig));
>  	elfcorebuf = NULL;
>  }
>  EXPORT_SYMBOL_GPL(vmcore_cleanup);
> 
> 
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> http://lists.infradead.org/mailman/listinfo/kexec
> 

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