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

Zhang Yanfei
2013-03-06T07:01:05Z

于 2013年03月02日 16:36, HATAYAMA Daisuke 写道:
> 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@jp.fujitsu.com>
> ---
>
> 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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