[PATCH 2/2] makedumpfile: make the incomplete vmcore generated by ENOSPC error analyzable
Dave Anderson
anderson at redhat.com
Tue Sep 16 06:20:13 PDT 2014
----- Original Message -----
> Date: Tue, 16 Sep 2014 17:48:49 +0800
> From: "Wang, Xiao/Wang Xiao" <wangx.fnst at cn.fujitsu.com>
> To: <kexec at lists.infradead.org>
> Subject: [PATCH 2/2] makedumpfile: make the incomplete vmcore
> generated by ENOSPC error analyzable
> Message-ID: <54180781.2080702 at cn.fujitsu.com>
> Content-Type: text/plain; charset="UTF-8"; format=flowed
>
> Since the incomplete vmcore generated by ENOSPC error can't be anylyzed by
> crash utility, but sometimes this file may contain important information
> and the panic problem won't be reproduced, then we came up with an idea to
> modify the exist data of the incomplete vmcore file to make it analyzable
> by crash utility. As there are two formats of the vmcore file, different
> methods are needed to deal with each of them,
This patch bothers me -- how would the crash utility know that the "fixed"
vmcore file was truncated/bogus to begin with? Are you simply presuming
that the user (when running makedumpfile) will change the output dumpfile
name to something that indicates that it's incomplete?
Typically incomplete vmcores fail to initialize due to some missing data,
and it will confuse the issue if the PT_LOAD segments indicate that everything
is just fine. There really should be some kind of indication/flag/note in the
compressed dumpfile or ELF header that it's a bogus/truncated vmcore.
Dave
>
> elf:
> Modify the value of the PT_LOAD program header to reflect the actual size
> of the incomplete vmcore file. This method can't be used to modify the
> vmcore written in flattened mode.
>
> kdump-compressed:
> Dump the bitmap before any page header and page data.
>
> Signed-of-by: Wang Xiao <wangx.fnst at cn.fujitsu.com>
> ---
> makedumpfile.c | 150
> +++++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 files changed, 143 insertions(+), 7 deletions(-)
>
> diff --git a/makedumpfile.c b/makedumpfile.c
> index ce4a866..debc15b 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -3621,6 +3621,128 @@ write_cache(struct cache_data *cd, void *buf,
> size_t size)
> }
>
> int
> +reserve_diskspace(int fd, off_t start_offset, off_t end_offset, char
> *file_name)
> +{
> + size_t buf_size;
> + char *buf = NULL;
> +
> + int ret = FALSE;
> +
> + if (start_offset >= end_offset) {
> + ERRMSG("The start offset of diskspace to be reserved must smaller than "
> + "the end offset.\n");
> + return FALSE;
> + }
> +
> + buf_size = end_offset - start_offset;
> +
> + if ((buf = malloc(buf_size)) == NULL) {
> + ERRMSG("Can't allocate memory for the size of reserved diskspace. %s\n",
> + strerror(errno));
> + return FALSE;
> + }
> +
> + memset(buf, 0, buf_size);
> + if (!write_buffer(fd, start_offset, buf, buf_size, file_name))
> + goto out;
> +
> + ret = TRUE;
> +out:
> + if (buf != NULL) {
> + free(buf);
> + }
> +
> + return ret;
> +}
> +
> +int
> +check_and_modify_elf_header() {
> + int i, phnum;
> + off_t file_end, offset, end_offset;
> + Elf64_Ehdr ehdr64;
> + Elf32_Ehdr ehdr32;
> + Elf64_Phdr phdr64;
> + Elf32_Phdr phdr32;
> +
> + /*
> + * the is_elf64_memory() function still can be used.
> + */
> + if (is_elf64_memory()) { /* ELF64 */
> + if (!get_elf64_ehdr(info->fd_dumpfile, info->name_dumpfile, &ehdr64)) {
> + ERRMSG("Can't get ehdr64.\n");
> + return FALSE;
> + }
> + phnum = ehdr64.e_phnum;
> + } else { /* ELF32 */
> + if (!get_elf32_ehdr(info->fd_dumpfile, info->name_dumpfile, &ehdr32)) {
> + ERRMSG("Can't get ehdr32.\n");
> + return FALSE;
> + }
> + phnum = ehdr32.e_phnum;
> + }
> +
> + file_end = lseek(info->fd_dumpfile, 0, SEEK_END);
> + if (file_end < 0) {
> + ERRMSG("Can't detect the size of %s. %s\n",
> + info->name_dumpfile,
> + strerror(errno));
> + return FALSE;
> + }
> +
> + for (i = 0; i < phnum; i++) {
> + if (is_elf64_memory()) {
> + if (!get_elf64_phdr(info->fd_dumpfile,
> + info->name_dumpfile,
> + i, &phdr64)) {
> + ERRMSG("Can't find Phdr %d.\n", i);
> + return FALSE;
> + }
> +
> + offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) * i;
> + end_offset = phdr64.p_offset + phdr64.p_filesz;
> +
> + /*
> + * Check the program header and modify its value according
> + * to the actual written size.
> + */
> + if (file_end >= end_offset)
> + continue;
> + else if (file_end >= phdr64.p_offset && file_end < end_offset)
> + phdr64.p_filesz = file_end - phdr64.p_offset;
> + else if (file_end < phdr64.p_offset)
> + memset(&phdr64, 0, sizeof(Elf64_Phdr));
> +
> + if (!write_buffer(info->fd_dumpfile, offset, &phdr64,
> + sizeof(Elf64_Phdr), info->name_dumpfile))
> + return FALSE;
> + } else {
> + if (!get_elf32_phdr(info->fd_dumpfile,
> + info->name_dumpfile,
> + i, &phdr32)) {
> + ERRMSG("Can't find Phdr %d.\n", i);
> + return FALSE;
> + }
> +
> + offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr) * i;
> + end_offset = phdr32.p_offset + phdr32.p_filesz;
> +
> + if (file_end >= end_offset)
> + continue;
> + else if (file_end >= phdr32.p_offset && file_end < end_offset)
> + phdr32.p_filesz = file_end - phdr32.p_offset;
> + else if (file_end < phdr32.p_offset)
> + memset(&phdr32, 0, sizeof(Elf32_Phdr));
> +
> + if (!write_buffer(info->fd_dumpfile, offset, &phdr32,
> + sizeof(Elf32_Phdr), info->name_dumpfile))
> + return FALSE;
> + }
> + }
> +
> + return TRUE;
> +}
> +
> +int
> write_cache_bufsz(struct cache_data *cd)
> {
> if (!cd->buf_size)
> @@ -5432,6 +5554,13 @@ write_elf_header(struct cache_data *cd_header)
> size_note = note.p_filesz;
>
> /*
> + * Reserve a space to store the whole program headers.
> + */
> + if (!reserve_diskspace(cd_header->fd, cd_header->offset,
> + offset_note_dumpfile, cd_header->file_name))
> + goto out;
> +
> + /*
> * Modify the note size in PT_NOTE header to accomodate eraseinfo data.
> * Eraseinfo will be written later.
> */
> @@ -6956,11 +7085,11 @@ write_kdump_pages_and_bitmap_cyclic(struct
> cache_data *cd_header, struct cache_d
> if (!exclude_unnecessary_pages_cyclic(&cycle))
> return FALSE;
>
> - if (!write_kdump_pages_cyclic(cd_header, cd_page, &pd_zero,
> - &offset_data, &cycle))
> + if (!write_kdump_bitmap2_cyclic(&cycle))
> return FALSE;
>
> - if (!write_kdump_bitmap2_cyclic(&cycle))
> + if (!write_kdump_pages_cyclic(cd_header, cd_page, &pd_zero,
> + &offset_data, &cycle))
> return FALSE;
> }
>
> @@ -7906,10 +8035,10 @@ writeout_dumpfile(void)
> goto out;
> if (info->flag_cyclic) {
> if (!write_elf_pages_cyclic(&cd_header, &cd_page))
> - goto out;
> + goto chk_enospc;
> } else {
> if (!write_elf_pages(&cd_header, &cd_page))
> - goto out;
> + goto chk_enospc;
> }
> if (!write_elf_eraseinfo(&cd_header))
> goto out;
> @@ -7923,12 +8052,12 @@ writeout_dumpfile(void)
> } else {
> if (!write_kdump_header())
> goto out;
> + if (!write_kdump_bitmap())
> + goto out;
> if (!write_kdump_pages(&cd_header, &cd_page))
> goto out;
> if (!write_kdump_eraseinfo(&cd_page))
> goto out;
> - if (!write_kdump_bitmap())
> - goto out;
> }
> if (info->flag_flatten) {
> if (!write_end_flat_header())
> @@ -7936,6 +8065,13 @@ writeout_dumpfile(void)
> }
>
> ret = TRUE;
> +chk_enospc:
> + if ((ret == FALSE) && info->flag_nospace && !info->flag_flatten) {
> + if (!write_cache_bufsz(&cd_header))
> + goto out;
> + if (!check_and_modify_elf_header())
> + ERRMSG("Can't modify the elf header.\n");
> + }
> out:
> free_cache_data(&cd_header);
> free_cache_data(&cd_page);
> --
> 1.7.1
>
>
>
>
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