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    Subject[PATCH v6 2/8] vmcore: allocate buffer for ELF headers on page-size alignment
    Date
    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.

    Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
    ---

    fs/proc/vmcore.c | 80 ++++++++++++++++++++++++++++++------------------------
    1 files changed, 45 insertions(+), 35 deletions(-)

    diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
    index ab0c92e..48886e6 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++;
    @@ -280,7 +281,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
    phdr.p_flags = 0;
    note_off = sizeof(Elf64_Ehdr) +
    (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf64_Phdr);
    - phdr.p_offset = note_off;
    + phdr.p_offset = roundup(note_off, PAGE_SIZE);
    phdr.p_vaddr = phdr.p_paddr = 0;
    phdr.p_filesz = phdr.p_memsz = phdr_sz;
    phdr.p_align = 0;
    @@ -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;
    @@ -361,7 +364,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
    phdr.p_flags = 0;
    note_off = sizeof(Elf32_Ehdr) +
    (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf32_Phdr);
    - phdr.p_offset = note_off;
    + phdr.p_offset = roundup(note_off, PAGE_SIZE);
    phdr.p_vaddr = phdr.p_paddr = 0;
    phdr.p_filesz = phdr.p_memsz = phdr_sz;
    phdr.p_align = 0;
    @@ -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;
    @@ -398,9 +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) +
    - phdr_ptr->p_memsz; /* Note sections */
    + vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);

    for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
    if (phdr_ptr->p_type != PT_LOAD)
    @@ -435,9 +438,7 @@ 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) +
    - phdr_ptr->p_memsz; /* Note sections */
    + vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);

    for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
    if (phdr_ptr->p_type != PT_LOAD)
    @@ -459,7 +460,7 @@ 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,
    +static void __init set_vmcore_list_offsets_elf64(char *elfptr, size_t elfsz,
    struct list_head *vc_list)
    {
    loff_t vmcore_off;
    @@ -469,8 +470,7 @@ static void __init set_vmcore_list_offsets_elf64(char *elfptr,
    ehdr_ptr = (Elf64_Ehdr *)elfptr;

    /* Skip Elf header and program headers. */
    - vmcore_off = sizeof(Elf64_Ehdr) +
    - (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr);
    + vmcore_off = elfsz;

    list_for_each_entry(m, vc_list, list) {
    m->offset = vmcore_off;
    @@ -479,7 +479,7 @@ static void __init set_vmcore_list_offsets_elf64(char *elfptr,
    }

    /* Sets offset fields of vmcore elements. */
    -static void __init set_vmcore_list_offsets_elf32(char *elfptr,
    +static void __init set_vmcore_list_offsets_elf32(char *elfptr, size_t elfsz,
    struct list_head *vc_list)
    {
    loff_t vmcore_off;
    @@ -489,8 +489,7 @@ static void __init set_vmcore_list_offsets_elf32(char *elfptr,
    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 +525,35 @@ 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_elf64(elfcorebuf, elfcorebuf_sz, &vmcore_list);
    return 0;
    }

    @@ -581,30 +585,35 @@ 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_elf32(elfcorebuf, elfcorebuf_sz, &vmcore_list);
    return 0;
    }

    @@ -629,14 +638,14 @@ 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 +692,8 @@ 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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