[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>

3 files changed, 29 insertions, 24 deletions

diff --git a/include/asm-i386/elf.h b/include/asm-i386/elf.h
index 952b3ee3c9b..d304ab4161f 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 3e9f610c35d..e5651b2a585 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>
diff --git a/include/linux/elf.h b/include/linux/elf.h
index 60713e6ea29..8b17ffe222c 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -83,6 +83,23 @@ typedef __s64	Elf64_Sxword;
 #define DT_DEBUG	21
 #define DT_TEXTREL	22
 #define DT_JMPREL	23
+#define DT_ENCODING	32
+#define OLD_DT_LOOS	0x60000000
+#define DT_LOOS		0x6000000d
+#define DT_HIOS		0x6ffff000
+#define DT_VALRNGLO	0x6ffffd00
+#define DT_VALRNGHI	0x6ffffdff
+#define DT_ADDRRNGLO	0x6ffffe00
+#define DT_ADDRRNGHI	0x6ffffeff
+#define DT_VERSYM	0x6ffffff0
+#define DT_RELACOUNT	0x6ffffff9
+#define DT_RELCOUNT	0x6ffffffa
+#define DT_FLAGS_1	0x6ffffffb
+#define DT_VERDEF	0x6ffffffc
+#define	DT_VERDEFNUM	0x6ffffffd
+#define DT_VERNEED	0x6ffffffe
+#define	DT_VERNEEDNUM	0x6fffffff
+#define OLD_DT_HIOS     0x6fffffff
 #define DT_LOPROC	0x70000000
 #define DT_HIPROC	0x7fffffff