[PATCH] i386 vDSO: use VM_ALWAYSDUMP

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>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/i386/kernel/sysenter.c b/arch/i386/kernel/sysenter.c
index 454d12df59ea..5da744204d10 100644
--- a/arch/i386/kernel/sysenter.c
+++ b/arch/i386/kernel/sysenter.c
@@ -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;