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    SubjectRe: [PATCH v2 01/20] vmcore: refer to e_phoff member explicitly
    于 2013年03月05日 15:35, Zhang Yanfei 写道:
    > 于 2013年03月02日 16:35, HATAYAMA Daisuke 写道:
    >> Code around /proc/vmcore currently assumes program header table is
    >> next to ELF header. But future change can break the assumption on
    >> kexec-tools and the 1st kernel. To avoid worst case, now refer to
    >> e_phoff member that indicates position of program header table in
    >> file-offset.
    >
    > Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
    >
    >>
    >> Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
    >> ---
    >>
    >> fs/proc/vmcore.c | 40 ++++++++++++++++++++--------------------
    >> 1 files changed, 20 insertions(+), 20 deletions(-)
    >>
    >> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
    >> index b870f74..abf4f01 100644
    >> --- a/fs/proc/vmcore.c
    >> +++ b/fs/proc/vmcore.c
    >> @@ -221,8 +221,8 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
    >> Elf64_Phdr *phdr_ptr;
    >>
    >> ehdr_ptr = (Elf64_Ehdr *)elfptr;
    >> - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
    >> - size = sizeof(Elf64_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr));
    >> + phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff);
    >> + size = ehdr_ptr->e_phoff + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr));
    >> for (i = 0; i < ehdr_ptr->e_phnum; i++) {
    >> size += phdr_ptr->p_memsz;
    >> phdr_ptr++;
    >> @@ -238,8 +238,8 @@ static u64 __init get_vmcore_size_elf32(char *elfptr)
    >> Elf32_Phdr *phdr_ptr;
    >>
    >> ehdr_ptr = (Elf32_Ehdr *)elfptr;
    >> - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
    >> - size = sizeof(Elf32_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr));
    >> + phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff);
    >> + size = ehdr_ptr->e_phoff + ((ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr));
    >> for (i = 0; i < ehdr_ptr->e_phnum; i++) {
    >> size += phdr_ptr->p_memsz;
    >> phdr_ptr++;
    >> @@ -259,7 +259,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
    >> u64 phdr_sz = 0, note_off;
    >>
    >> ehdr_ptr = (Elf64_Ehdr *)elfptr;
    >> - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
    >> + phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff);
    >> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
    >> int j;
    >> void *notes_section;
    >> @@ -305,7 +305,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
    >> /* Prepare merged PT_NOTE program header. */
    >> phdr.p_type = PT_NOTE;
    >> phdr.p_flags = 0;
    >> - note_off = sizeof(Elf64_Ehdr) +
    >> + note_off = ehdr_ptr->e_phoff +
    >> (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf64_Phdr);
    >> phdr.p_offset = note_off;
    >> phdr.p_vaddr = phdr.p_paddr = 0;
    >> @@ -313,14 +313,14 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
    >> phdr.p_align = 0;
    >>
    >> /* Add merged PT_NOTE program header*/
    >> - tmp = elfptr + sizeof(Elf64_Ehdr);
    >> + tmp = elfptr + ehdr_ptr->e_phoff;
    >> memcpy(tmp, &phdr, sizeof(phdr));
    >> tmp += sizeof(phdr);
    >>
    >> /* Remove unwanted PT_NOTE program headers. */
    >> i = (nr_ptnote - 1) * sizeof(Elf64_Phdr);
    >> *elfsz = *elfsz - i;
    >> - memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr)));
    >> + memmove(tmp, tmp+i, ((*elfsz)-ehdr_ptr->e_phoff-sizeof(Elf64_Phdr)));
    >>
    >> /* Modify e_phnum to reflect merged headers. */
    >> ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
    >> @@ -340,7 +340,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
    >> u64 phdr_sz = 0, note_off;
    >>
    >> ehdr_ptr = (Elf32_Ehdr *)elfptr;
    >> - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
    >> + phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff);
    >> for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
    >> int j;
    >> void *notes_section;
    >> @@ -386,7 +386,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
    >> /* Prepare merged PT_NOTE program header. */
    >> phdr.p_type = PT_NOTE;
    >> phdr.p_flags = 0;
    >> - note_off = sizeof(Elf32_Ehdr) +
    >> + note_off = ehdr_ptr->e_phoff +
    >> (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf32_Phdr);
    >> phdr.p_offset = note_off;
    >> phdr.p_vaddr = phdr.p_paddr = 0;
    >> @@ -394,14 +394,14 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
    >> phdr.p_align = 0;
    >>
    >> /* Add merged PT_NOTE program header*/
    >> - tmp = elfptr + sizeof(Elf32_Ehdr);
    >> + tmp = elfptr + ehdr_ptr->e_phoff;
    >> memcpy(tmp, &phdr, sizeof(phdr));
    >> tmp += sizeof(phdr);
    >>
    >> /* Remove unwanted PT_NOTE program headers. */
    >> i = (nr_ptnote - 1) * sizeof(Elf32_Phdr);
    >> *elfsz = *elfsz - i;
    >> - memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf32_Ehdr)-sizeof(Elf32_Phdr)));
    >> + memmove(tmp, tmp+i, ((*elfsz)-ehdr_ptr->e_phoff-sizeof(Elf32_Phdr)));
    >>
    >> /* Modify e_phnum to reflect merged headers. */
    >> ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;
    >> @@ -422,10 +422,10 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
    >> struct vmcore *new;
    >>
    >> ehdr_ptr = (Elf64_Ehdr *)elfptr;
    >> - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */
    >> + phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */
    >>
    >> /* First program header is PT_NOTE header. */
    >> - vmcore_off = sizeof(Elf64_Ehdr) +
    >> + vmcore_off = ehdr_ptr->e_phoff +
    >> (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr) +
    >> phdr_ptr->p_memsz; /* Note sections */
    >>
    >> @@ -459,10 +459,10 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
    >> struct vmcore *new;
    >>
    >> ehdr_ptr = (Elf32_Ehdr *)elfptr;
    >> - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */
    >> + phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */
    >>
    >> /* First program header is PT_NOTE header. */
    >> - vmcore_off = sizeof(Elf32_Ehdr) +
    >> + vmcore_off = ehdr_ptr->e_phoff +
    >> (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr) +
    >> phdr_ptr->p_memsz; /* Note sections */
    >>
    >> @@ -496,7 +496,7 @@ 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) +
    >> + vmcore_off = ehdr_ptr->e_phoff +
    >> (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr);
    >>
    >> list_for_each_entry(m, vc_list, list) {
    >> @@ -516,7 +516,7 @@ 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) +
    >> + vmcore_off = ehdr_ptr->e_phoff +
    >> (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr);
    >>
    >> list_for_each_entry(m, vc_list, list) {
    >> @@ -553,7 +553,7 @@ 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_sz = ehdr.e_phoff + ehdr.e_phnum * sizeof(Elf64_Phdr);

    One minor suggestion.

    Previously, when the code assumes program headers are following immediately
    the ELF header, it uses

    elfcorebuf_sz = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);

    to calculate the size of ELF header and ELF program headers

    This patch avoids the assumption, and uses ehdr.e_phoff to get the program
    headers' address. But it will read unrelated contents into elfcorebuf if
    program headers are not following immediately the ELF header. So could the
    code be:

    elfcorebuf_sz = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);
    addr = elfcorehdr_addr + ehdr.e_phoff;
    memcpy(elfcorebuf, &ehdr, sizeof(Elf64_Ehdr));
    read_from_oldmem(elfcorebuf + sizeof(Elf64_Ehdr), elfcorebuf_sz -
    sizeof(Elf64_Ehdr), &addr, 0);
    (Elf64_Ehdr *)elfcorebuf->e_phoff = sizeof(Elf64_Ehdr);

    >> elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
    >> if (!elfcorebuf)
    >> return -ENOMEM;
    >> @@ -608,7 +608,7 @@ 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_sz = ehdr.e_phoff + ehdr.e_phnum * sizeof(Elf32_Phdr);
    >> elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
    >> if (!elfcorebuf)
    >> return -ENOMEM;
    >>
    >>
    >> _______________________________________________
    >> kexec mailing list
    >> kexec@lists.infradead.org
    >> http://lists.infradead.org/mailman/listinfo/kexec
    >>
    >
    >
    > _______________________________________________
    > kexec mailing list
    > kexec@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/kexec

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