x86 vDSO: ia32 sysenter_return

This changes the 64-bit kernel's support for the 32-bit sysenter
instruction to use stored fields rather than constants for the
user-mode return address, as the 32-bit kernel does.  This adds a
sysenter_return field to struct thread_info, as 32-bit has.  There
is no observable effect from this yet.  It makes the assembly code
independent of the 32-bit vDSO mapping address, paving the way for
making the vDSO address vary as it does on the 32-bit kernel.

[ akpm@linux-foundation.org: build fix on !CONFIG_IA32_EMULATION ]

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

4 files changed, 13 insertions, 4 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index df588f0f76e1..2499a324feaa 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -12,7 +12,6 @@
 #include <asm/ia32_unistd.h>    
 #include <asm/thread_info.h>    
 #include <asm/segment.h>
-#include <asm/vsyscall32.h>
 #include <asm/irqflags.h>
 #include <linux/linkage.h>
 
@@ -104,7 +103,7 @@ ENTRY(ia32_sysenter_target)
         pushfq
         CFI_ADJUST_CFA_OFFSET 8
         /*CFI_REL_OFFSET rflags,0*/
-        movl    $VSYSCALL32_SYSEXIT, %r10d
+        movl    8*3-THREAD_SIZE+threadinfo_sysenter_return(%rsp), %r10d
         CFI_REGISTER rip,r10
         pushq   $__USER32_CS
         CFI_ADJUST_CFA_OFFSET 8
@@ -142,6 +141,8 @@ sysenter_do_call:
         andl    $~TS_COMPAT,threadinfo_status(%r10)
         /* clear IF, that popfq doesn't enable interrupts early */
         andl  $~0x200,EFLAGS-R11(%rsp) 
+        movl    RIP-R11(%rsp),%edx              /* User %eip */
+        CFI_REGISTER rip,rdx
         RESTORE_ARGS 1,24,1,1,1,1
         popfq
         CFI_ADJUST_CFA_OFFSET -8
@@ -149,8 +150,6 @@ sysenter_do_call:
         popq    %rcx                            /* User %esp */
         CFI_ADJUST_CFA_OFFSET -8
         CFI_REGISTER rsp,rcx
-        movl    $VSYSCALL32_SYSEXIT,%edx        /* User %eip */
-        CFI_REGISTER rip,rdx
         TRACE_IRQS_ON
         swapgs
         sti             /* sti only takes effect after the next instruction */
diff --git a/arch/x86/ia32/syscall32.c b/arch/x86/ia32/syscall32.c
index d751d96c2ef2..98ff99f5b59a 100644
--- a/arch/x86/ia32/syscall32.c
+++ b/arch/x86/ia32/syscall32.c
@@ -46,6 +46,10 @@ int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
                                       VM_ALWAYSDUMP,
                                       syscall32_pages);
+        if (ret == 0) {
+                current->mm->context.vdso = (void __user *)VSYSCALL32_BASE;
+                current_thread_info()->sysenter_return = VSYSCALL32_SYSEXIT;
+        }
         up_write(&mm->mmap_sem);
         return ret;
 }
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 40f41752c1df..c27c646214f4 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -46,6 +46,9 @@ int main(void)
         ENTRY(addr_limit);
         ENTRY(preempt_count);
         ENTRY(status);
+#ifdef CONFIG_IA32_EMULATION
+        ENTRY(sysenter_return);
+#endif
         BLANK();
 #undef ENTRY
 #define ENTRY(entry) DEFINE(pda_ ## entry, offsetof(struct x8664_pda, entry))
diff --git a/include/asm-x86/thread_info_64.h b/include/asm-x86/thread_info_64.h
index 1ac23c157231..c8e7736fc792 100644
--- a/include/asm-x86/thread_info_64.h
+++ b/include/asm-x86/thread_info_64.h
@@ -33,6 +33,9 @@ struct thread_info {
 
         mm_segment_t            addr_limit;     
         struct restart_block    restart_block;
+#ifdef CONFIG_IA32_EMULATION
+        void __user             *sysenter_return;
+#endif
 };
 #endif