[PATCH] Fix CONFIG_COMPAT_VDSO

I wouldn't mind if CONFIG_COMPAT_VDSO went away entirely.  But if it's there,
it should work properly.  Currently it's quite haphazard: both real vma and
fixmap are mapped, both are put in the two different AT_* slots, sysenter
returns to the vma address rather than the fixmap address, and core dumps yet
are another story.

This patch makes CONFIG_COMPAT_VDSO disable the real vma and use the fixmap
area consistently.  This makes it actually compatible with what the old vdso
implementation did.
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>

arch/i386/kernel/entry.S

@@ -302,12 +302,16 @@ sysenter_past_esp:
 	pushl $(__USER_CS)
 	CFI_ADJUST_CFA_OFFSET 4
 	/*CFI_REL_OFFSET cs, 0*/
+#ifndef CONFIG_COMPAT_VDSO
 	/*
 	 * Push current_thread_info()->sysenter_return to the stack.
 	 * A tiny bit of offset fixup is necessary - 4*4 means the 4 words
 	 * pushed above; +8 corresponds to copy_thread's esp0 setting.
 	 */
 	pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)
+#else
+	pushl $SYSENTER_RETURN
+#endif
 	CFI_ADJUST_CFA_OFFSET 4
 	CFI_REL_OFFSET eip, 0
 

arch/i386/kernel/sysenter.c

@@ -100,6 +100,7 @@ int __init sysenter_setup(void)
 	return 0;
 }
 
+#ifndef CONFIG_COMPAT_VDSO
 static struct page *syscall_nopage(struct vm_area_struct *vma,
 				unsigned long adr, int *type)
 {
@@ -187,3 +188,4 @@ int in_gate_area_no_task(unsigned long addr)
 {
 	return 0;
 }
+#endif

include/asm-i386/elf.h

@@ -143,11 +143,8 @@ extern int dump_task_extended_fpu (struct task_struct *, struct user_fxsr_struct
 # define VDSO_PRELINK		0
 #endif
 
-#define VDSO_COMPAT_SYM(x) \
-		(VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK)
-
 #define VDSO_SYM(x) \
-		(VDSO_BASE + (unsigned long)(x) - VDSO_PRELINK)
+		(VDSO_COMPAT_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)
@@ -156,10 +153,12 @@ extern void __kernel_vsyscall;
 
 #define VDSO_ENTRY		VDSO_SYM(&__kernel_vsyscall)
 
+#ifndef CONFIG_COMPAT_VDSO
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
                                        int executable_stack);
+#endif
 
 extern unsigned int vdso_enabled;
 

include/asm-i386/fixmap.h

@@ -23,6 +23,8 @@
 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
 
 #ifndef __ASSEMBLY__

include/asm-i386/page.h

@@ -143,7 +143,9 @@ extern int page_is_ram(unsigned long pagenr);
 #include <asm-generic/memory_model.h>
 #include <asm-generic/page.h>
 
+#ifndef CONFIG_COMPAT_VDSO
 #define __HAVE_ARCH_GATE_AREA 1
+#endif
 #endif /* __KERNEL__ */
 
 #endif /* _I386_PAGE_H */