[PATCH] i386: Relocate VDSO ELF headers to match mapped location with COMPAT_VDSO

Some versions of libc can't deal with a VDSO which doesn't have its
ELF headers matching its mapped address.  COMPAT_VDSO maps the VDSO at
a specific system-wide fixed address.  Previously this was all done at
build time, on the grounds that the fixed VDSO address is always at
the top of the address space.  However, a hypervisor may reserve some
of that address space, pushing the fixmap address down.

This patch does the adjustment dynamically at runtime, depending on
the runtime location of the VDSO fixmap.

[ Patch has been through several hands: Jan Beulich wrote the orignal
  version; Zach reworked it, and Jeremy converted it to relocate phdrs
  as well as sections. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: "Jan Beulich" <JBeulich@novell.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>

2 files changed, 12 insertions, 24 deletions

diff --git a/include/asm-i386/elf.h b/include/asm-i386/elf.h
index 952b3ee3c9bb..d304ab4161ff 100644
--- a/include/asm-i386/elf.h
+++ b/include/asm-i386/elf.h
@@ -133,39 +133,31 @@ extern int dump_task_extended_fpu (struct task_struct *, struct user_fxsr_struct
 #define ELF_CORE_COPY_XFPREGS(tsk, elf_xfpregs) dump_task_extended_fpu(tsk, elf_xfpregs)
 
 #define VDSO_HIGH_BASE          (__fix_to_virt(FIX_VDSO))
-#define VDSO_BASE               ((unsigned long)current->mm->context.vdso)
-
-#ifdef CONFIG_COMPAT_VDSO
-# define VDSO_COMPAT_BASE       VDSO_HIGH_BASE
-# define VDSO_PRELINK           VDSO_HIGH_BASE
-#else
-# define VDSO_COMPAT_BASE       VDSO_BASE
-# define VDSO_PRELINK           0
-#endif
+#define VDSO_CURRENT_BASE       ((unsigned long)current->mm->context.vdso)
+#define VDSO_PRELINK            0
 
 #define VDSO_SYM(x) \
-                (VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK)
+                (VDSO_CURRENT_BASE + (unsigned long)(x) - VDSO_PRELINK)
 
 #define VDSO_HIGH_EHDR          ((const struct elfhdr *) VDSO_HIGH_BASE)
-#define VDSO_EHDR               ((const struct elfhdr *) VDSO_COMPAT_BASE)
+#define VDSO_EHDR               ((const struct elfhdr *) VDSO_CURRENT_BASE)
 
 extern void __kernel_vsyscall;
 
 #define VDSO_ENTRY              VDSO_SYM(&__kernel_vsyscall)
 
-#ifndef CONFIG_COMPAT_VDSO
-#define ARCH_HAS_SETUP_ADDITIONAL_PAGES
 struct linux_binprm;
+
+#define ARCH_HAS_SETUP_ADDITIONAL_PAGES
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
                                        int executable_stack);
-#endif
 
 extern unsigned int vdso_enabled;
 
-#define ARCH_DLINFO                                             \
-do if (vdso_enabled) {                                          \
-                NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY);            \
-                NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE); \
+#define ARCH_DLINFO                                                     \
+do if (vdso_enabled) {                                                  \
+                NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY);                    \
+                NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE);        \
 } while (0)
 
 #endif
diff --git a/include/asm-i386/fixmap.h b/include/asm-i386/fixmap.h
index 3e9f610c35df..e5651b2a585a 100644
--- a/include/asm-i386/fixmap.h
+++ b/include/asm-i386/fixmap.h
@@ -19,13 +19,9 @@
  * Leave one empty page between vmalloc'ed areas and
  * the start of the fixmap.
  */
-#ifndef CONFIG_COMPAT_VDSO
 extern unsigned long __FIXADDR_TOP;
-#else
-#define __FIXADDR_TOP  0xfffff000
-#define FIXADDR_USER_START      __fix_to_virt(FIX_VDSO)
-#define FIXADDR_USER_END        __fix_to_virt(FIX_VDSO - 1)
-#endif
+#define FIXADDR_USER_START     __fix_to_virt(FIX_VDSO)
+#define FIXADDR_USER_END       __fix_to_virt(FIX_VDSO - 1)
 
 #ifndef __ASSEMBLY__
 #include <linux/kernel.h>