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>

1 files changed, 3 insertions, 0 deletions

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))