linux-kernel - [PATCH RFC 1/4] x86/thread_info: add TIF

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Date:   Mon,  8 Jan 2018 17:12:16 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     tglx@...utronix.de, gnomes@...rguk.ukuu.org.uk,
        torvalds@...ux-foundation.org, Willy Tarreau <w@....eu>
Subject: [PATCH RFC 1/4] x86/thread_info: add TIF_NOPTI to disable PTI per task

This flag indicates that the task will not use isolated page tables.

Signed-off-by: Willy Tarreau <w@....eu>
---
 arch/x86/include/asm/thread_info.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 0022333..2f92cf1 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -126,6 +126,14 @@ struct thread_info {
 #define _TIF_X32		(1 << TIF_X32)
 #define _TIF_FSCHECK		(1 << TIF_FSCHECK)
 
+/* The following flags only exist on x86-64. We can't use the shift anymore
+ * due to C using signed ints by default and asm using unsigned longs.
+ */
+#ifdef CONFIG_X86_64
+# define  TIF_NOPTI		32	/* disable PTI for this task */
+# define _TIF_NOPTI		0x0000000100000000
+#endif
+
 /*
  * work to do in syscall_trace_enter().  Also includes TIF_NOHZ for
  * enter_from_user_mode()
-- 
1.7.12.1