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Message-ID: <51948872.5090402@cn.fujitsu.com>
Date: Thu, 16 May 2013 15:19:14 +0800
From: Zhang Yanfei <zhangyanfei@...fujitsu.com>
To: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
CC: vgoyal@...hat.com, 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,
jingbai.ma@...com, linux-mm@...ck.org, riel@...hat.com,
walken@...gle.com, hughd@...gle.com, kosaki.motohiro@...fujitsu.com
Subject: Re: [PATCH v6 6/8] vmcore: allocate ELF note segment in the 2nd kernel
vmalloc memory
于 2013年05月15日 17:06, HATAYAMA Daisuke 写道:
> The reasons why we don't allocate ELF note segment in the 1st kernel
> (old memory) on page boundary is to keep backward compatibility for
> old kernels, and that if doing so, we waste not a little memory due to
> round-up operation to fit the memory to page boundary since most of
> the buffers are in per-cpu area.
>
> ELF notes are per-cpu, so total size of ELF note segments depends on
> number of CPUs. The current maximum number of CPUs on x86_64 is 5192,
> and there's already system with 4192 CPUs in SGI, where total size
> amounts to 1MB. This can be larger in the near future or possibly even
> now on another architecture that has larger size of note per a single
> cpu. Thus, to avoid the case where memory allocation for large block
> fails, we allocate vmcore objects on vmalloc memory.
>
> This patch adds elfnotes_buf and elfnotes_sz variables to keep pointer
> to the ELF note segment buffer and its size. There's no longer the
> vmcore object that corresponds to the ELF note segment in
> vmcore_list. Accordingly, read_vmcore() has new case for ELF note
> segment and set_vmcore_list_offsets_elf{64,32}() and other helper
> functions starts calculating offset from sum of size of ELF headers
> and size of ELF note segment.
>
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
> ---
Acked-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
>
> fs/proc/vmcore.c | 273 +++++++++++++++++++++++++++++++++++++++++-------------
> 1 files changed, 209 insertions(+), 64 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 6cf7fbd..4e121fda 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -34,6 +34,9 @@ static char *elfcorebuf;
> static size_t elfcorebuf_sz;
> static size_t elfcorebuf_sz_orig;
>
> +static char *elfnotes_buf;
> +static size_t elfnotes_sz;
> +
> /* Total size of vmcore file. */
> static u64 vmcore_size;
>
> @@ -154,6 +157,26 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
> return acc;
> }
>
> + /* Read Elf note segment */
> + if (*fpos < elfcorebuf_sz + elfnotes_sz) {
> + void *kaddr;
> +
> + tsz = elfcorebuf_sz + elfnotes_sz - *fpos;
> + if (buflen < tsz)
> + tsz = buflen;
> + kaddr = elfnotes_buf + *fpos - elfcorebuf_sz;
> + if (copy_to_user(buffer, kaddr, tsz))
> + return -EFAULT;
> + buflen -= tsz;
> + *fpos += tsz;
> + buffer += tsz;
> + acc += tsz;
> +
> + /* leave now if filled buffer already */
> + if (buflen == 0)
> + return acc;
> + }
> +
> list_for_each_entry(m, &vmcore_list, list) {
> if (*fpos < m->offset + m->size) {
> tsz = m->offset + m->size - *fpos;
> @@ -221,23 +244,33 @@ static u64 __init get_vmcore_size_elf32(char *elfptr, size_t elfsz)
> return size;
> }
>
> -/* Merges all the PT_NOTE headers into one. */
> -static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
> - struct list_head *vc_list)
> +/**
> + * process_note_headers_elf64 - Perform a variety of processing on ELF
> + * note segments according to the combination of function arguments.
> + *
> + * @ehdr_ptr - ELF header buffer
> + * @nr_notes - the number of program header entries of PT_NOTE type
> + * @notes_sz - total size of ELF note segment
> + * @notes_buf - buffer into which ELF note segment is copied
> + *
> + * Assume @ehdr_ptr is always not NULL. If @nr_notes is not NULL, then
> + * the number of program header entries of PT_NOTE type is assigned to
> + * @nr_notes. If @notes_sz is not NULL, then total size of ELF note
> + * segment, header part plus data part, is assigned to @notes_sz. If
> + * @notes_buf is not NULL, then ELF note segment is copied into
> + * @notes_buf.
> + */
> +static int __init process_note_headers_elf64(const Elf64_Ehdr *ehdr_ptr,
> + int *nr_notes, u64 *notes_sz,
> + char *notes_buf)
> {
> int i, nr_ptnote=0, rc=0;
> - char *tmp;
> - Elf64_Ehdr *ehdr_ptr;
> - Elf64_Phdr phdr, *phdr_ptr;
> + Elf64_Phdr *phdr_ptr = (Elf64_Phdr*)(ehdr_ptr + 1);
> Elf64_Nhdr *nhdr_ptr;
> - u64 phdr_sz = 0, note_off;
> + u64 phdr_sz = 0;
>
> - ehdr_ptr = (Elf64_Ehdr *)elfptr;
> - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
> - int j;
> void *notes_section;
> - struct vmcore *new;
> u64 offset, max_sz, sz, real_sz = 0;
> if (phdr_ptr->p_type != PT_NOTE)
> continue;
> @@ -253,7 +286,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
> return rc;
> }
> nhdr_ptr = notes_section;
> - for (j = 0; j < max_sz; j += sz) {
> + while (real_sz < max_sz) {
> if (nhdr_ptr->n_namesz == 0)
> break;
> sz = sizeof(Elf64_Nhdr) +
> @@ -262,20 +295,68 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
> real_sz += sz;
> nhdr_ptr = (Elf64_Nhdr*)((char*)nhdr_ptr + sz);
> }
> -
> - /* Add this contiguous chunk of notes section to vmcore list.*/
> - new = get_new_element();
> - if (!new) {
> - kfree(notes_section);
> - return -ENOMEM;
> + if (notes_buf) {
> + offset = phdr_ptr->p_offset;
> + rc = read_from_oldmem(notes_buf + phdr_sz, real_sz,
> + &offset, 0);
> + if (rc < 0) {
> + kfree(notes_section);
> + return rc;
> + }
> }
> - new->paddr = phdr_ptr->p_offset;
> - new->size = real_sz;
> - list_add_tail(&new->list, vc_list);
> phdr_sz += real_sz;
> kfree(notes_section);
> }
>
> + if (nr_notes)
> + *nr_notes = nr_ptnote;
> + if (notes_sz)
> + *notes_sz = phdr_sz;
> +
> + return 0;
> +}
> +
> +static int __init get_note_number_and_size_elf64(const Elf64_Ehdr *ehdr_ptr,
> + int *nr_ptnote, u64 *phdr_sz)
> +{
> + return process_note_headers_elf64(ehdr_ptr, nr_ptnote, phdr_sz, NULL);
> +}
> +
> +static int __init copy_notes_elf64(const Elf64_Ehdr *ehdr_ptr, char *notes_buf)
> +{
> + return process_note_headers_elf64(ehdr_ptr, NULL, NULL, notes_buf);
> +}
> +
> +/* Merges all the PT_NOTE headers into one. */
> +static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
> + char **notes_buf, size_t *notes_sz)
> +{
> + int i, nr_ptnote=0, rc=0;
> + char *tmp;
> + Elf64_Ehdr *ehdr_ptr;
> + Elf64_Phdr phdr;
> + u64 phdr_sz = 0, note_off;
> + struct vm_struct *vm;
> +
> + ehdr_ptr = (Elf64_Ehdr *)elfptr;
> +
> + rc = get_note_number_and_size_elf64(ehdr_ptr, &nr_ptnote, &phdr_sz);
> + if (rc < 0)
> + return rc;
> +
> + *notes_sz = roundup(phdr_sz, PAGE_SIZE);
> + *notes_buf = vzalloc(*notes_sz);
> + if (!*notes_buf)
> + return -ENOMEM;
> +
> + vm = find_vm_area(*notes_buf);
> + BUG_ON(!vm);
> + vm->flags |= VM_USERMAP;
> +
> + rc = copy_notes_elf64(ehdr_ptr, *notes_buf);
> + if (rc < 0)
> + return rc;
> +
> /* Prepare merged PT_NOTE program header. */
> phdr.p_type = PT_NOTE;
> phdr.p_flags = 0;
> @@ -304,23 +385,33 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
> return 0;
> }
>
> -/* Merges all the PT_NOTE headers into one. */
> -static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
> - struct list_head *vc_list)
> +/**
> + * process_note_headers_elf32 - Perform a variety of processing on ELF
> + * note segments according to the combination of function arguments.
> + *
> + * @ehdr_ptr - ELF header buffer
> + * @nr_notes - the number of program header entries of PT_NOTE type
> + * @notes_sz - total size of ELF note segment
> + * @notes_buf - buffer into which ELF note segment is copied
> + *
> + * Assume @ehdr_ptr is always not NULL. If @nr_notes is not NULL, then
> + * the number of program header entries of PT_NOTE type is assigned to
> + * @nr_notes. If @notes_sz is not NULL, then total size of ELF note
> + * segment, header part plus data part, is assigned to @notes_sz. If
> + * @notes_buf is not NULL, then ELF note segment is copied into
> + * @notes_buf.
> + */
> +static int __init process_note_headers_elf32(const Elf32_Ehdr *ehdr_ptr,
> + int *nr_notes, u64 *notes_sz,
> + char *notes_buf)
> {
> int i, nr_ptnote=0, rc=0;
> - char *tmp;
> - Elf32_Ehdr *ehdr_ptr;
> - Elf32_Phdr phdr, *phdr_ptr;
> + Elf32_Phdr *phdr_ptr = (Elf32_Phdr*)(ehdr_ptr + 1);
> Elf32_Nhdr *nhdr_ptr;
> - u64 phdr_sz = 0, note_off;
> + u64 phdr_sz = 0;
>
> - ehdr_ptr = (Elf32_Ehdr *)elfptr;
> - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
> - int j;
> void *notes_section;
> - struct vmcore *new;
> u64 offset, max_sz, sz, real_sz = 0;
> if (phdr_ptr->p_type != PT_NOTE)
> continue;
> @@ -336,7 +427,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
> return rc;
> }
> nhdr_ptr = notes_section;
> - for (j = 0; j < max_sz; j += sz) {
> + while (real_sz < max_sz) {
> if (nhdr_ptr->n_namesz == 0)
> break;
> sz = sizeof(Elf32_Nhdr) +
> @@ -345,20 +436,68 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
> real_sz += sz;
> nhdr_ptr = (Elf32_Nhdr*)((char*)nhdr_ptr + sz);
> }
> -
> - /* Add this contiguous chunk of notes section to vmcore list.*/
> - new = get_new_element();
> - if (!new) {
> - kfree(notes_section);
> - return -ENOMEM;
> + if (notes_buf) {
> + offset = phdr_ptr->p_offset;
> + rc = read_from_oldmem(notes_buf + phdr_sz, real_sz,
> + &offset, 0);
> + if (rc < 0) {
> + kfree(notes_section);
> + return rc;
> + }
> }
> - new->paddr = phdr_ptr->p_offset;
> - new->size = real_sz;
> - list_add_tail(&new->list, vc_list);
> phdr_sz += real_sz;
> kfree(notes_section);
> }
>
> + if (nr_notes)
> + *nr_notes = nr_ptnote;
> + if (notes_sz)
> + *notes_sz = phdr_sz;
> +
> + return 0;
> +}
> +
> +static int __init get_note_number_and_size_elf32(const Elf32_Ehdr *ehdr_ptr,
> + int *nr_ptnote, u64 *phdr_sz)
> +{
> + return process_note_headers_elf32(ehdr_ptr, nr_ptnote, phdr_sz, NULL);
> +}
> +
> +static int __init copy_notes_elf32(const Elf32_Ehdr *ehdr_ptr, char *notes_buf)
> +{
> + return process_note_headers_elf32(ehdr_ptr, NULL, NULL, notes_buf);
> +}
> +
> +/* Merges all the PT_NOTE headers into one. */
> +static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
> + char **notes_buf, size_t *notes_sz)
> +{
> + int i, nr_ptnote=0, rc=0;
> + char *tmp;
> + Elf32_Ehdr *ehdr_ptr;
> + Elf32_Phdr phdr;
> + u64 phdr_sz = 0, note_off;
> + struct vm_struct *vm;
> +
> + ehdr_ptr = (Elf32_Ehdr *)elfptr;
> +
> + rc = get_note_number_and_size_elf32(ehdr_ptr, &nr_ptnote, &phdr_sz);
> + if (rc < 0)
> + return rc;
> +
> + *notes_sz = roundup(phdr_sz, PAGE_SIZE);
> + *notes_buf = vzalloc(*notes_sz);
> + if (!*notes_buf)
> + return -ENOMEM;
> +
> + vm = find_vm_area(*notes_buf);
> + BUG_ON(!vm);
> + vm->flags |= VM_USERMAP;
> +
> + rc = copy_notes_elf32(ehdr_ptr, *notes_buf);
> + if (rc < 0)
> + return rc;
> +
> /* Prepare merged PT_NOTE program header. */
> phdr.p_type = PT_NOTE;
> phdr.p_flags = 0;
> @@ -391,6 +530,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
> * the new offset fields of exported program headers. */
> static int __init process_ptload_program_headers_elf64(char *elfptr,
> size_t elfsz,
> + size_t elfnotes_sz,
> struct list_head *vc_list)
> {
> int i;
> @@ -402,8 +542,8 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
> ehdr_ptr = (Elf64_Ehdr *)elfptr;
> phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */
>
> - /* First program header is PT_NOTE header. */
> - vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);
> + /* Skip Elf header, program headers and Elf note segment. */
> + vmcore_off = elfsz + elfnotes_sz;
>
> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
> u64 paddr, start, end, size;
> @@ -433,6 +573,7 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
>
> static int __init process_ptload_program_headers_elf32(char *elfptr,
> size_t elfsz,
> + size_t elfnotes_sz,
> struct list_head *vc_list)
> {
> int i;
> @@ -444,8 +585,8 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
> ehdr_ptr = (Elf32_Ehdr *)elfptr;
> phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */
>
> - /* First program header is PT_NOTE header. */
> - vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);
> + /* Skip Elf header, program headers and Elf note segment. */
> + vmcore_off = elfsz + elfnotes_sz;
>
> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
> u64 paddr, start, end, size;
> @@ -474,17 +615,15 @@ 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, size_t elfsz,
> +static void __init set_vmcore_list_offsets_elf64(size_t elfsz,
> + size_t elfnotes_sz,
> 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 = elfsz;
> + /* Skip Elf header, program headers and Elf note segment. */
> + vmcore_off = elfsz + elfnotes_sz;
>
> list_for_each_entry(m, vc_list, list) {
> m->offset = vmcore_off;
> @@ -493,17 +632,15 @@ static void __init set_vmcore_list_offsets_elf64(char *elfptr, size_t elfsz,
> }
>
> /* Sets offset fields of vmcore elements. */
> -static void __init set_vmcore_list_offsets_elf32(char *elfptr, size_t elfsz,
> +static void __init set_vmcore_list_offsets_elf32(size_t elfsz,
> + size_t elfnotes_sz,
> 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 = elfsz;
> + /* Skip Elf header, program headers and Elf note segment. */
> + vmcore_off = elfsz + elfnotes_sz;
>
> list_for_each_entry(m, vc_list, list) {
> m->offset = vmcore_off;
> @@ -554,20 +691,23 @@ static int __init parse_crash_elf64_headers(void)
> }
>
> /* Merge all PT_NOTE headers into one. */
> - rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
> + rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz,
> + &elfnotes_buf, &elfnotes_sz);
> if (rc) {
> free_pages((unsigned long)elfcorebuf,
> get_order(elfcorebuf_sz_orig));
> return rc;
> }
> rc = process_ptload_program_headers_elf64(elfcorebuf, elfcorebuf_sz,
> - &vmcore_list);
> + elfnotes_sz,
> + &vmcore_list);
> if (rc) {
> free_pages((unsigned long)elfcorebuf,
> get_order(elfcorebuf_sz_orig));
> return rc;
> }
> - set_vmcore_list_offsets_elf64(elfcorebuf, elfcorebuf_sz, &vmcore_list);
> + set_vmcore_list_offsets_elf64(elfcorebuf_sz, elfnotes_sz,
> + &vmcore_list);
> return 0;
> }
>
> @@ -614,20 +754,23 @@ static int __init parse_crash_elf32_headers(void)
> }
>
> /* Merge all PT_NOTE headers into one. */
> - rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
> + rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz,
> + &elfnotes_buf, &elfnotes_sz);
> if (rc) {
> free_pages((unsigned long)elfcorebuf,
> get_order(elfcorebuf_sz_orig));
> return rc;
> }
> rc = process_ptload_program_headers_elf32(elfcorebuf, elfcorebuf_sz,
> - &vmcore_list);
> + elfnotes_sz,
> + &vmcore_list);
> if (rc) {
> free_pages((unsigned long)elfcorebuf,
> get_order(elfcorebuf_sz_orig));
> return rc;
> }
> - set_vmcore_list_offsets_elf32(elfcorebuf, elfcorebuf_sz, &vmcore_list);
> + set_vmcore_list_offsets_elf32(elfcorebuf_sz, elfnotes_sz,
> + &vmcore_list);
> return 0;
> }
>
> @@ -706,6 +849,8 @@ void vmcore_cleanup(void)
> list_del(&m->list);
> kfree(m);
> }
> + vfree(elfnotes_buf);
> + elfnotes_buf = NULL;
> free_pages((unsigned long)elfcorebuf,
> get_order(elfcorebuf_sz_orig));
> elfcorebuf = NULL;
>
>
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