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[PATCH] kdump: Parse elf32 headers and export through /proc/vmcore
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o Adds support for parsing core ELF32 headers.
o I am expecting ELF32 support to go away down the line. This patch has been
  introduced for testing purposes as gdb can not parse ELF64 headers for
  i386. When a decent user space solution is available, ELF32 support
  can go away.

Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Vivek Goyal authored and Linus Torvalds committed Jun 25, 2005
1 parent 666bfdd commit 72658e9
Showing 1 changed file with 218 additions and 0 deletions.
218 changes: 218 additions & 0 deletions fs/proc/vmcore.c
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Original file line number Diff line number Diff line change
Expand Up @@ -202,6 +202,23 @@ static u64 __init get_vmcore_size_elf64(char *elfptr)
return size;
}

static u64 __init get_vmcore_size_elf32(char *elfptr)
{
int i;
u64 size;
Elf32_Ehdr *ehdr_ptr;
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));
for (i = 0; i < ehdr_ptr->e_phnum; i++) {
size += phdr_ptr->p_memsz;
phdr_ptr++;
}
return size;
}

/* Merges all the PT_NOTE headers into one. */
static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
struct list_head *vc_list)
Expand Down Expand Up @@ -283,6 +300,87 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
return 0;
}

/* Merges all the PT_NOTE headers into one. */
static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
struct list_head *vc_list)
{
int i, nr_ptnote=0, rc=0;
char *tmp;
Elf32_Ehdr *ehdr_ptr;
Elf32_Phdr phdr, *phdr_ptr;
Elf32_Nhdr *nhdr_ptr;
u64 phdr_sz = 0, note_off;

ehdr_ptr = (Elf32_Ehdr *)elfptr;
phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
int j;
void *notes_section;
struct vmcore *new;
u64 offset, max_sz, sz, real_sz = 0;
if (phdr_ptr->p_type != PT_NOTE)
continue;
nr_ptnote++;
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;
}
nhdr_ptr = notes_section;
for (j = 0; j < max_sz; j += sz) {
if (nhdr_ptr->n_namesz == 0)
break;
sz = sizeof(Elf32_Nhdr) +
((nhdr_ptr->n_namesz + 3) & ~3) +
((nhdr_ptr->n_descsz + 3) & ~3);
real_sz += sz;
nhdr_ptr = (Elf32_Nhdr*)((char*)nhdr_ptr + sz);
}

/* Add this contiguous chunk of notes section to vmcore list.*/
new = get_new_element();
if (!new) {
kfree(notes_section);
return -ENOMEM;
}
new->paddr = phdr_ptr->p_offset;
new->size = real_sz;
list_add_tail(&new->list, vc_list);
phdr_sz += real_sz;
kfree(notes_section);
}

/* Prepare merged PT_NOTE program header. */
phdr.p_type = PT_NOTE;
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_vaddr = phdr.p_paddr = 0;
phdr.p_filesz = phdr.p_memsz = phdr_sz;
phdr.p_align = 0;

/* Add merged PT_NOTE program header*/
tmp = elfptr + sizeof(Elf32_Ehdr);
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)));

/* Modify e_phnum to reflect merged headers. */
ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;

return 0;
}

/* Add memory chunks represented by program headers to vmcore list. Also update
* the new offset fields of exported program headers. */
static int __init process_ptload_program_headers_elf64(char *elfptr,
Expand Down Expand Up @@ -322,6 +420,43 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
return 0;
}

static int __init process_ptload_program_headers_elf32(char *elfptr,
size_t elfsz,
struct list_head *vc_list)
{
int i;
Elf32_Ehdr *ehdr_ptr;
Elf32_Phdr *phdr_ptr;
loff_t vmcore_off;
struct vmcore *new;

ehdr_ptr = (Elf32_Ehdr *)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 */

for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
if (phdr_ptr->p_type != PT_LOAD)
continue;

/* Add this contiguous chunk of memory to vmcore list.*/
new = get_new_element();
if (!new)
return -ENOMEM;
new->paddr = phdr_ptr->p_offset;
new->size = phdr_ptr->p_memsz;
list_add_tail(&new->list, vc_list);

/* Update the program header offset */
phdr_ptr->p_offset = vmcore_off;
vmcore_off = vmcore_off + phdr_ptr->p_memsz;
}
return 0;
}

/* Sets offset fields of vmcore elements. */
static void __init set_vmcore_list_offsets_elf64(char *elfptr,
struct list_head *vc_list)
Expand All @@ -342,6 +477,26 @@ 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,
struct list_head *vc_list)
{
loff_t vmcore_off;
Elf32_Ehdr *ehdr_ptr;
struct vmcore *m;

ehdr_ptr = (Elf32_Ehdr *)elfptr;

/* Skip Elf header and program headers. */
vmcore_off = sizeof(Elf32_Ehdr) +
(ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr);

list_for_each_entry(m, vc_list, list) {
m->offset = vmcore_off;
vmcore_off += m->size;
}
}

static int __init parse_crash_elf64_headers(void)
{
int rc=0;
Expand Down Expand Up @@ -398,6 +553,62 @@ static int __init parse_crash_elf64_headers(void)
return 0;
}

static int __init parse_crash_elf32_headers(void)
{
int rc=0;
Elf32_Ehdr ehdr;
u64 addr;

addr = elfcorehdr_addr;

/* Read Elf header */
rc = read_from_oldmem((char*)&ehdr, sizeof(Elf32_Ehdr), &addr, 0);
if (rc < 0)
return rc;

/* Do some basic Verification. */
if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0 ||
(ehdr.e_type != ET_CORE) ||
!elf_check_arch(&ehdr) ||
ehdr.e_ident[EI_CLASS] != ELFCLASS32||
ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
ehdr.e_version != EV_CURRENT ||
ehdr.e_ehsize != sizeof(Elf32_Ehdr) ||
ehdr.e_phentsize != sizeof(Elf32_Phdr) ||
ehdr.e_phnum == 0) {
printk(KERN_WARNING "Warning: Core image elf header is not"
"sane\n");
return -EINVAL;
}

/* Read in all elf headers. */
elfcorebuf_sz = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
if (!elfcorebuf)
return -ENOMEM;
addr = elfcorehdr_addr;
rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0);
if (rc < 0) {
kfree(elfcorebuf);
return rc;
}

/* Merge all PT_NOTE headers into one. */
rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
if (rc) {
kfree(elfcorebuf);
return rc;
}
rc = process_ptload_program_headers_elf32(elfcorebuf, elfcorebuf_sz,
&vmcore_list);
if (rc) {
kfree(elfcorebuf);
return rc;
}
set_vmcore_list_offsets_elf32(elfcorebuf, &vmcore_list);
return 0;
}

static int __init parse_crash_elf_headers(void)
{
unsigned char e_ident[EI_NIDENT];
Expand All @@ -421,6 +632,13 @@ static int __init parse_crash_elf_headers(void)

/* Determine vmcore size. */
vmcore_size = get_vmcore_size_elf64(elfcorebuf);
} 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);
} else {
printk(KERN_WARNING "Warning: Core image elf header is not"
" sane\n");
Expand Down

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