[tip:x86/asm] x86/asm/entry, perf: Fix incorrect TIF_IA32 check in code_segment_base()

[tip-bot for Andy Lutomirski <tipbot@zytor.com>]

Commit-ID:  c56716af8d27ca8dd6e45445ae1c0a05fd9753a6
Gitweb:     http://git.kernel.org/tip/c56716af8d27ca8dd6e45445ae1c0a05fd9753a6
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 18 Mar 2015 18:33:28 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 23 Mar 2015 10:08:21 +0100

x86/asm/entry, perf: Fix incorrect TIF_IA32 check in code_segment_base()

We want to check whether user code is in 32-bit mode, not
whether the task is nominally 32-bit.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/33e5107085ce347a8303560302b15c2cadd62c4c.1426728647.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/perf_event.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index b71a7f8..979963b 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2161,10 +2161,9 @@ static unsigned long code_segment_base(struct pt_regs *regs)
 	if (user_mode(regs) && regs->cs != __USER_CS)
 		return get_segment_base(regs->cs);
 #else
-	if (test_thread_flag(TIF_IA32)) {
-		if (user_mode(regs) && regs->cs != __USER32_CS)
-			return get_segment_base(regs->cs);
-	}
+	if (user_mode(regs) && !user_64bit_mode(regs) &&
+	    regs->cs != __USER32_CS)
+		return get_segment_base(regs->cs);
 #endif
 	return 0;
 }