[tip:x86/asm] x86/vdso: Track each mm' s loaded vDSO image as well as its base

[tip-bot for Andy Lutomirski]

Commit-ID:  352b78c62f27b356b182008acd3117f3ee03ffd2
Gitweb:     http://git.kernel.org/tip/352b78c62f27b356b182008acd3117f3ee03ffd2
Author:     Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Tue, 29 Dec 2015 20:12:21 -0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 12 Jan 2016 11:59:34 +0100

x86/vdso: Track each mm's loaded vDSO image as well as its base

As we start to do more intelligent things with the vDSO at
runtime (as opposed to just at mm initialization time), we'll
need to know which vDSO is in use.

In principle, we could guess based on the mm type, but that's
over-complicated and error-prone.  Instead, just track it in the
mmu context.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/c99ac48681bad709ca7ad5ee899d9042a3af6b00.1451446564.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/entry/vdso/vma.c  | 1 +
 arch/x86/include/asm/mmu.h | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index b8f69e2..80b0210 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -121,6 +121,7 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 
 	text_start = addr - image->sym_vvar_start;
 	current->mm->context.vdso = (void __user *)text_start;
+	current->mm->context.vdso_image = image;
 
 	/*
 	 * MAYWRITE to allow gdb to COW and set breakpoints
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 55234d5..1ea0bae 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -19,7 +19,8 @@ typedef struct {
 #endif
 
 	struct mutex lock;
-	void __user *vdso;
+	void __user *vdso;			/* vdso base address */
+	const struct vdso_image *vdso_image;	/* vdso image in use */
 
 	atomic_t perf_rdpmc_allowed;	/* nonzero if rdpmc is allowed */
 } mm_context_t;