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Message-ID: <20130523142226.GD2779@redhat.com>
Date: Thu, 23 May 2013 10:22:26 -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,
riel@...hat.com, walken@...gle.com, hughd@...gle.com,
kosaki.motohiro@...fujitsu.com
Subject: Re: [PATCH v8 2/9] vmcore: allocate buffer for ELF headers on
page-size alignment
On Thu, May 23, 2013 at 02:25:07PM +0900, HATAYAMA Daisuke wrote:
> Allocate ELF headers on page-size boundary using __get_free_pages()
> instead of kmalloc().
>
> Later patch will merge PT_NOTE entries into a single unique one and
> decrease the buffer size actually used. Keep original buffer size in
> variable elfcorebuf_sz_orig to kfree the buffer later and actually
> used buffer size with rounded up to page-size boundary in variable
> elfcorebuf_sz separately.
>
> The size of part of the ELF buffer exported from /proc/vmcore is
> elfcorebuf_sz.
>
> The merged, removed PT_NOTE entries, i.e. the range [elfcorebuf_sz,
> elfcorebuf_sz_orig], is filled with 0.
>
> Use size of the ELF headers as an initial offset value in
> set_vmcore_list_offsets_elf{64,32} and
> process_ptload_program_headers_elf{64,32} in order to indicate that
> the offset includes the holes towards the page boundary.
>
> As a result, both set_vmcore_list_offsets_elf{64,32} have the same
> definition. Merge them as set_vmcore_list_offsets.
>
> 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 | 94 ++++++++++++++++++++++++------------------------------
> 1 files changed, 42 insertions(+), 52 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index ab0c92e..80fea97 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -32,6 +32,7 @@ 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;
> @@ -186,7 +187,7 @@ static struct vmcore* __init get_new_element(void)
> return kzalloc(sizeof(struct vmcore), GFP_KERNEL);
> }
>
> -static u64 __init get_vmcore_size_elf64(char *elfptr)
> +static u64 __init get_vmcore_size_elf64(char *elfptr, size_t elfsz)
> {
> int i;
> u64 size;
> @@ -195,7 +196,7 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
>
> ehdr_ptr = (Elf64_Ehdr *)elfptr;
> phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
> - size = sizeof(Elf64_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr));
> + size = elfsz;
> for (i = 0; i < ehdr_ptr->e_phnum; i++) {
> size += phdr_ptr->p_memsz;
> phdr_ptr++;
> @@ -203,7 +204,7 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
> return size;
> }
>
> -static u64 __init get_vmcore_size_elf32(char *elfptr)
> +static u64 __init get_vmcore_size_elf32(char *elfptr, size_t elfsz)
> {
> int i;
> u64 size;
> @@ -212,7 +213,7 @@ static u64 __init get_vmcore_size_elf32(char *elfptr)
>
> ehdr_ptr = (Elf32_Ehdr *)elfptr;
> phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
> - size = sizeof(Elf32_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr));
> + size = elfsz;
> for (i = 0; i < ehdr_ptr->e_phnum; i++) {
> size += phdr_ptr->p_memsz;
> phdr_ptr++;
> @@ -294,6 +295,8 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
> i = (nr_ptnote - 1) * sizeof(Elf64_Phdr);
> *elfsz = *elfsz - i;
> memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr)));
> + memset(elfptr + *elfsz, 0, i);
> + *elfsz = roundup(*elfsz, PAGE_SIZE);
>
> /* Modify e_phnum to reflect merged headers. */
> ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
> @@ -375,6 +378,8 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
> i = (nr_ptnote - 1) * sizeof(Elf32_Phdr);
> *elfsz = *elfsz - i;
> memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf32_Ehdr)-sizeof(Elf32_Phdr)));
> + memset(elfptr + *elfsz, 0, i);
> + *elfsz = roundup(*elfsz, PAGE_SIZE);
>
> /* Modify e_phnum to reflect merged headers. */
> ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
> @@ -398,8 +403,7 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
> phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */
>
> /* First program header is PT_NOTE header. */
> - vmcore_off = sizeof(Elf64_Ehdr) +
> - (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr) +
> + vmcore_off = elfsz +
> phdr_ptr->p_memsz; /* Note sections */
>
> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
> @@ -435,8 +439,7 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
> phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */
>
> /* First program header is PT_NOTE header. */
> - vmcore_off = sizeof(Elf32_Ehdr) +
> - (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr) +
> + vmcore_off = elfsz +
> phdr_ptr->p_memsz; /* Note sections */
>
> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
> @@ -459,38 +462,14 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
> }
>
> /* Sets offset fields of vmcore elements. */
> -static void __init set_vmcore_list_offsets_elf64(char *elfptr,
> - struct list_head *vc_list)
> +static void __init set_vmcore_list_offsets(size_t elfsz,
> + struct list_head *vc_list)
> {
> loff_t vmcore_off;
> - Elf64_Ehdr *ehdr_ptr;
> struct vmcore *m;
>
> - ehdr_ptr = (Elf64_Ehdr *)elfptr;
> -
> - /* Skip Elf header and program headers. */
> - vmcore_off = sizeof(Elf64_Ehdr) +
> - (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr);
> -
> - list_for_each_entry(m, vc_list, list) {
> - m->offset = vmcore_off;
> - vmcore_off += m->size;
> - }
> -}
> -
> -/* Sets offset fields of vmcore elements. */
> -static void __init set_vmcore_list_offsets_elf32(char *elfptr,
> - struct list_head *vc_list)
> -{
> - loff_t vmcore_off;
> - Elf32_Ehdr *ehdr_ptr;
> - struct vmcore *m;
> -
> - ehdr_ptr = (Elf32_Ehdr *)elfptr;
> -
> /* Skip Elf header and program headers. */
> - vmcore_off = sizeof(Elf32_Ehdr) +
> - (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr);
> + vmcore_off = elfsz;
>
> list_for_each_entry(m, vc_list, list) {
> m->offset = vmcore_off;
> @@ -526,30 +505,35 @@ static int __init parse_crash_elf64_headers(void)
> }
>
> /* Read in all elf headers. */
> - elfcorebuf_sz = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);
> - elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
> + elfcorebuf_sz_orig = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);
> + elfcorebuf_sz = elfcorebuf_sz_orig;
> + 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);
> + rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &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);
> + set_vmcore_list_offsets(elfcorebuf_sz, &vmcore_list);
> return 0;
> }
>
> @@ -581,30 +565,35 @@ static int __init parse_crash_elf32_headers(void)
> }
>
> /* Read in all elf headers. */
> - elfcorebuf_sz = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
> - elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
> + elfcorebuf_sz_orig = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
> + elfcorebuf_sz = elfcorebuf_sz_orig;
> + 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);
> + rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &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);
> + set_vmcore_list_offsets(elfcorebuf_sz, &vmcore_list);
> return 0;
> }
>
> @@ -629,14 +618,14 @@ static int __init parse_crash_elf_headers(void)
> return rc;
>
> /* Determine vmcore size. */
> - vmcore_size = get_vmcore_size_elf64(elfcorebuf);
> + vmcore_size = get_vmcore_size_elf64(elfcorebuf, elfcorebuf_sz);
> } 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);
> + vmcore_size = get_vmcore_size_elf32(elfcorebuf, elfcorebuf_sz);
> } else {
> pr_warn("Warning: Core image elf header is not sane\n");
> return -EINVAL;
> @@ -683,7 +672,8 @@ 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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