linux-kernel - [RFC 12/30] x86/entry/64/compat: Disable SYSENTER and SYSCALL32 entries

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Message-Id: <9fd0ce4a9d607aa91461d5380118a45d7f73b37f.1441146105.git.luto@kernel.org>
Date:	Tue,  1 Sep 2015 15:41:12 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC 12/30] x86/entry/64/compat: Disable SYSENTER and SYSCALL32 entries

We've disabled the vDSO helpers to call them, so turn off the
entries entirely (temporarily) in preparation for cleaning them up.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/entry/entry_64_compat.S | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 1432d60a1f4a..e11aa38696fe 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -103,6 +103,14 @@ ENTRY(entry_SYSENTER_compat)
 	jnz	sysenter_fix_flags
 sysenter_flags_fixed:
 
+	/* Temporary: SYSENTER is disabled. */
+#ifdef CONFIG_CONTEXT_TRACKING
+	call enter_from_user_mode
+#endif
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	movl $11, %edi
+	call do_exit
+
 	/*
 	 * Re-enable interrupts.  IRQ tracing already thinks that IRQs are
 	 * on (since we treat user mode as having IRQs on), and the
@@ -324,6 +332,11 @@ ENTRY(entry_SYSCALL_compat)
 	 * it is too small to ever cause noticeable irq latency.
 	 */
 	SWAPGS_UNSAFE_STACK
+
+	/* Temporary: SYSCALL32 is disabled. */
+	movl	$-ENOSYS, %eax
+	USERGS_SYSRET32
+
 	movl	%esp, %r8d
 	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
 	ENABLE_INTERRUPTS(CLBR_NONE)
-- 
2.4.3

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