[RFC Patch 5/6] slimdump: Capture slimdump for fatal MCE generated crashes

K.Prasad
2011-05-26T17:23:29Z

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 <prasad@linux.vnet.ibm.com>
---
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) {