slimdump: Capture slimdump for fatal MCE generated crashes System crashes resulting from fatal hardware errors (such as MCE) don't need all the contents from crashing-kernel's memory. Generate a new 'slimdump' that retains only essential information while discarding the old memory.
Signed-off-by: K.Prasad <[email protected]> --- fs/proc/vmcore.c | 130 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 128 insertions(+), 2 deletions(-) Index: linux-2.6.slim_kdump/fs/proc/vmcore.c =================================================================== --- linux-2.6.slim_kdump.orig/fs/proc/vmcore.c +++ linux-2.6.slim_kdump/fs/proc/vmcore.c @@ -483,9 +483,60 @@ static void __init set_vmcore_list_offse } } +/* + * Check if the crash was due to a fatal Memory Check Exception + */ +static int is_mce_crash64(void) +{ + int i, j, len = 0, rc; + Elf64_Ehdr *ehdr_ptr; + Elf64_Phdr *phdr_ptr; + Elf64_Nhdr *nhdr_ptr; + + ehdr_ptr = (Elf64_Ehdr *)elfcorebuf; + phdr_ptr = (Elf64_Phdr *)(elfcorebuf + sizeof(Elf64_Ehdr)); + + for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { + void *notes_section; + u64 offset, max_sz; + if (phdr_ptr->p_type != PT_NOTE) + continue; + max_sz = phdr_ptr->p_memsz; + offset = phdr_ptr->p_offset; + notes_section = kmalloc(max_sz, GFP_KERNEL); + if (!notes_section) + return -ENOMEM; + rc = read_from_oldmem(notes_section, max_sz, &offset, 0); + if (rc < 0) { + kfree(notes_section); + return rc; + } + + for (j = 0; j < phdr_ptr->p_filesz; j += len) { + nhdr_ptr = notes_section + j; + if (nhdr_ptr->n_type == NT_MCE) + { + kfree(notes_section); + return 1; + } + /* + * The elf-64 standard specifies 8-byte alignment while + * append_elf_note function does only 4-byte roundup. + * Hence this code also does a 4-byte roundup. + */ + len = sizeof(Elf64_Nhdr); + len = roundup(len + nhdr_ptr->n_namesz, 4); + len = roundup(len + nhdr_ptr->n_descsz, 4); + } + kfree(notes_section); + } + return 0; +} + static int __init parse_crash_elf64_headers(void) { - int rc=0; + int i, rc = 0; + Elf64_Phdr *phdr_ptr; Elf64_Ehdr ehdr; u64 addr; @@ -523,6 +574,18 @@ static int __init parse_crash_elf64_head return rc; } + phdr_ptr = (Elf64_Phdr *)(elfcorebuf + sizeof(Elf64_Ehdr)); + if (is_mce_crash64() > 0) { + /* + * If crash is due to Machine Check exception, don't populate + * sections other than elf-notes. Mark their sizes as zero. + */ + for (i = 0; i < ehdr.e_phnum; i++, phdr_ptr++) { + if (phdr_ptr->p_type != PT_NOTE) + phdr_ptr->p_memsz = phdr_ptr->p_filesz = 0; + } + } + /* Merge all PT_NOTE headers into one. */ rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list); if (rc) { @@ -539,9 +602,60 @@ static int __init parse_crash_elf64_head return 0; } +/* + * Check if the crash was due to a fatal Memory Check Exception + */ +static int is_mce_crash32(void) +{ + int i, j, len = 0, rc; + Elf32_Ehdr *ehdr_ptr; + Elf32_Phdr *phdr_ptr; + Elf32_Nhdr *nhdr_ptr; + + ehdr_ptr = (Elf32_Ehdr *)elfcorebuf; + phdr_ptr = (Elf32_Phdr *)(elfcorebuf + sizeof(Elf32_Ehdr)); + + for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { + void *notes_section; + u64 offset, max_sz; + if (phdr_ptr->p_type != PT_NOTE) + continue; + max_sz = phdr_ptr->p_memsz; + offset = phdr_ptr->p_offset; + notes_section = kmalloc(max_sz, GFP_KERNEL); + if (!notes_section) + return -ENOMEM; + rc = read_from_oldmem(notes_section, max_sz, &offset, 0); + if (rc < 0) { + kfree(notes_section); + return rc; + } + + for (j = 0; j < phdr_ptr->p_filesz; j += len) { + nhdr_ptr = notes_section + j; + if (nhdr_ptr->n_type == NT_MCE) + { + kfree(notes_section); + return 1; + } + /* + * The elf-64 standard specifies 8-byte alignment while + * append_elf_note function does only 4-byte roundup. + * Hence this code also does a 4-byte roundup. + */ + len = sizeof(Elf64_Nhdr); + len = roundup(len + nhdr_ptr->n_namesz, 4); + len = roundup(len + nhdr_ptr->n_descsz, 4); + } + kfree(notes_section); + } + return 0; +} + static int __init parse_crash_elf32_headers(void) { - int rc=0; + int i, rc = 0; + Elf32_Phdr *phdr_ptr; Elf32_Ehdr ehdr; u64 addr; @@ -579,6 +693,18 @@ static int __init parse_crash_elf32_head return rc; } + phdr_ptr = (Elf32_Phdr *)(elfcorebuf + sizeof(Elf32_Ehdr)); + if (is_mce_crash32() > 0) { + /* + * If crash is due to Machine Check exception, don't populate + * sections other than elf-notes. Mark their sizes as zero. + */ + for (i = 0; i < ehdr.e_phnum; i++, phdr_ptr++) { + if (phdr_ptr->p_type != PT_NOTE) + phdr_ptr->p_memsz = phdr_ptr->p_filesz = 0; + } + } + /* Merge all PT_NOTE headers into one. */ rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list); if (rc) { _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
