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[PATCH] i386 vDSO: use VM_ALWAYSDUMP

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This patch fixes core dumps to include the vDSO vma, which is left out now.
It removes the special-case core writing macros, which were not doing the
right thing for the vDSO vma anyway.  Instead, it uses VM_ALWAYSDUMP in the
vma; there is no need for the fixmap page to be installed.  It handles the
CONFIG_COMPAT_VDSO case by making elf_core_dump use the fake vma from
get_gate_vma after real vmas in the same way the /proc/PID/maps code does.

This changes core dumps so they no longer include the non-PT_LOAD phdrs from
the vDSO.  I made the change to add them in the first place, but in turned out
that nothing ever wanted them there since the advent of NT_AUXV.  It's cleaner
to leave them out, and just let the phdrs inside the vDSO image speak for
themselves.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2007-01-26 00:56:49 -08:00 committed by Linus Torvalds
parent e5b97dde51
commit f47aef55d9
4 changed files with 49 additions and 52 deletions
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12
arch/i386/kernel/sysenter.c
View file

@ -79,11 +79,6 @@ int __init sysenter_setup(void)
#ifdef CONFIG_COMPAT_VDSO
__set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY);
printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
#else
/*
* In the non-compat case the ELF coredumping code needs the fixmap:
*/
__set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO);
#endif
if (!boot_cpu_has(X86_FEATURE_SEP)) {
@ -147,6 +142,13 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
vma->vm_end = addr + PAGE_SIZE;
/* MAYWRITE to allow gdb to COW and set breakpoints */
vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
/*
* Make sure the vDSO gets into every core dump.
* Dumping its contents makes post-mortem fully interpretable later
* without matching up the same kernel and hardware config to see
* what PC values meant.
*/
vma->vm_flags |= VM_ALWAYSDUMP;
vma->vm_flags |= mm->def_flags;
vma->vm_page_prot = protection_map[vma->vm_flags & 7];
vma->vm_ops = &syscall_vm_ops;

38
fs/binfmt_elf.c
View file

@ -1428,6 +1428,32 @@ static int elf_dump_thread_status(long signr, struct elf_thread_status *t)
return sz;
}
static struct vm_area_struct *first_vma(struct task_struct *tsk,
struct vm_area_struct *gate_vma)
{
struct vm_area_struct *ret = tsk->mm->mmap;
if (ret)
return ret;
return gate_vma;
}
/*
* Helper function for iterating across a vma list. It ensures that the caller
* will visit `gate_vma' prior to terminating the search.
*/
static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
struct vm_area_struct *gate_vma)
{
struct vm_area_struct *ret;
ret = this_vma->vm_next;
if (ret)
return ret;
if (this_vma == gate_vma)
return NULL;
return gate_vma;
}
/*
* Actual dumper
*
@ -1443,7 +1469,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
int segs;
size_t size = 0;
int i;
struct vm_area_struct *vma;
struct vm_area_struct *vma, *gate_vma;
struct elfhdr *elf = NULL;
loff_t offset = 0, dataoff, foffset;
unsigned long limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
@ -1529,6 +1555,10 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
segs += ELF_CORE_EXTRA_PHDRS;
#endif
gate_vma = get_gate_vma(current);
if (gate_vma != NULL)
segs++;
/* Set up header */
fill_elf_header(elf, segs + 1); /* including notes section */
@ -1596,7 +1626,8 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
/* Write program headers for segments dump */
for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
for (vma = first_vma(current, gate_vma); vma != NULL;
vma = next_vma(vma, gate_vma)) {
struct elf_phdr phdr;
size_t sz;
@ -1645,7 +1676,8 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
/* Align to page */
DUMP_SEEK(dataoff - foffset);
for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
for (vma = first_vma(current, gate_vma); vma != NULL;
vma = next_vma(vma, gate_vma)) {
unsigned long addr;
if (!maydump(vma))

44
include/asm-i386/elf.h
View file

@ -168,50 +168,6 @@ do if (vdso_enabled) { \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE); \
} while (0)
/*
* These macros parameterize elf_core_dump in fs/binfmt_elf.c to write out
* extra segments containing the vsyscall DSO contents. Dumping its
* contents makes post-mortem fully interpretable later without matching up
* the same kernel and hardware config to see what PC values meant.
* Dumping its extra ELF program headers includes all the other information
* a debugger needs to easily find how the vsyscall DSO was being used.
*/
#define ELF_CORE_EXTRA_PHDRS (VDSO_HIGH_EHDR->e_phnum)
#define ELF_CORE_WRITE_EXTRA_PHDRS \
do { \
const struct elf_phdr *const vsyscall_phdrs = \
(const struct elf_phdr *) (VDSO_HIGH_BASE \
+ VDSO_HIGH_EHDR->e_phoff); \
int i; \
Elf32_Off ofs = 0; \
for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) { \
struct elf_phdr phdr = vsyscall_phdrs[i]; \
if (phdr.p_type == PT_LOAD) { \
BUG_ON(ofs != 0); \
ofs = phdr.p_offset = offset; \
phdr.p_memsz = PAGE_ALIGN(phdr.p_memsz); \
phdr.p_filesz = phdr.p_memsz; \
offset += phdr.p_filesz; \
} \
else \
phdr.p_offset += ofs; \
phdr.p_paddr = 0; /* match other core phdrs */ \
DUMP_WRITE(&phdr, sizeof(phdr)); \
} \
} while (0)
#define ELF_CORE_WRITE_EXTRA_DATA \
do { \
const struct elf_phdr *const vsyscall_phdrs = \
(const struct elf_phdr *) (VDSO_HIGH_BASE \
+ VDSO_HIGH_EHDR->e_phoff); \
int i; \
for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) { \
if (vsyscall_phdrs[i].p_type == PT_LOAD) \
DUMP_WRITE((void *) vsyscall_phdrs[i].p_vaddr, \
PAGE_ALIGN(vsyscall_phdrs[i].p_memsz)); \
} \
} while (0)
#endif
#endif

7
mm/memory.c
View file

@ -2608,6 +2608,13 @@ static int __init gate_vma_init(void)
gate_vma.vm_end = FIXADDR_USER_END;
gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
gate_vma.vm_page_prot = __P101;
/*
* Make sure the vDSO gets into every core dump.
* Dumping its contents makes post-mortem fully interpretable later
* without matching up the same kernel and hardware config to see
* what PC values meant.
*/
gate_vma.vm_flags |= VM_ALWAYSDUMP;
return 0;
}
__initcall(gate_vma_init);