linux-kernel - [RFC PTI 2/3] Revert "x86/mm/pti: Disable native VSYSCALL"

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Message-Id: <d7c374c734cc0a47613f943ac17fdb8582ebd3c6.1512763129.git.luto@kernel.org>
Date:   Fri,  8 Dec 2017 11:59:10 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [RFC PTI 2/3] Revert "x86/mm/pti: Disable native VSYSCALL"

This reverts commit 6a7b4041b853ecc653e2c1dda5b736ab5fd29357.

With the PGD-propagation logic simplified, there's no need for this.
---
 arch/x86/Kconfig | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 411838058194..babb1e53b0a6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2233,9 +2233,6 @@ choice
 
 	config LEGACY_VSYSCALL_NATIVE
 		bool "Native"
-		# The VSYSCALL page comes from the kernel page tables
-		# and is not available when PAGE_TABLE_ISOLATION is enabled.
-		depends on !PAGE_TABLE_ISOLATION
 		help
 		  Actual executable code is located in the fixed vsyscall
 		  address mapping, implementing time() efficiently. Since
@@ -2253,11 +2250,6 @@ choice
 		  exploits. This configuration is recommended when userspace
 		  still uses the vsyscall area.
 
-		  When PAGE_TABLE_ISOLATION is enabled, the vsyscall area will become
-		  unreadable.  This emulation option still works, but PAGE_TABLE_ISOLATION
-		  will make it harder to do things like trace code using the
-		  emulation.
-
 	config LEGACY_VSYSCALL_NONE
 		bool "None"
 		help
-- 
2.13.6