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From: tip-bot for Dominik Brodowski <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: hpa@zytor.com, torvalds@linux-foundation.org, mingo@kernel.org,
	luto@kernel.org, linux@dominikbrodowski.net, bp@alien8.de,
	linux-kernel@vger.kernel.org, peterz@infradead.org,
	brgerst@gmail.com, jpoimboe@redhat.com, dvlasenk@redhat.com,
	tglx@linutronix.de
Subject: [tip:x86/pti] x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro
Date: Mon, 12 Feb 2018 02:17:27 -0800	[thread overview]
Message-ID: <tip-7b7b09f110f06f3c006e9b3f4590f7d9ba91345b@git.kernel.org> (raw)
In-Reply-To: <20180211104949.12992-5-linux@dominikbrodowski.net>

Commit-ID:  7b7b09f110f06f3c006e9b3f4590f7d9ba91345b
Gitweb:     https://git.kernel.org/tip/7b7b09f110f06f3c006e9b3f4590f7d9ba91345b
Author:     Dominik Brodowski <linux@dominikbrodowski.net>
AuthorDate: Sun, 11 Feb 2018 11:49:45 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 12 Feb 2018 08:06:36 +0100

x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro

Those instances where ALLOC_PT_GPREGS_ON_STACK is called just before
SAVE_AND_CLEAR_REGS can trivially be replaced by PUSH_AND_CLEAN_REGS.
This macro uses PUSH instead of MOV and should therefore be faster, at
least on newer CPUs.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Link: http://lkml.kernel.org/r/20180211104949.12992-5-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/entry/calling.h  | 36 ++++++++++++++++++++++++++++++++++++
 arch/x86/entry/entry_64.S |  6 ++----
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index a05cbb8..57b1b87 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -137,6 +137,42 @@ For 32-bit we have the following conventions - kernel is built with
 	UNWIND_HINT_REGS offset=\offset
 	.endm
 
+	.macro PUSH_AND_CLEAR_REGS
+	/*
+	 * Push registers and sanitize registers of values that a
+	 * speculation attack might otherwise want to exploit. The
+	 * lower registers are likely clobbered well before they
+	 * could be put to use in a speculative execution gadget.
+	 * Interleave XOR with PUSH for better uop scheduling:
+	 */
+	pushq   %rdi		/* pt_regs->di */
+	pushq   %rsi		/* pt_regs->si */
+	pushq   %rdx		/* pt_regs->dx */
+	pushq   %rcx		/* pt_regs->cx */
+	pushq   %rax		/* pt_regs->ax */
+	pushq   %r8		/* pt_regs->r8 */
+	xorq    %r8, %r8	/* nospec   r8 */
+	pushq   %r9		/* pt_regs->r9 */
+	xorq    %r9, %r9	/* nospec   r9 */
+	pushq   %r10		/* pt_regs->r10 */
+	xorq    %r10, %r10	/* nospec   r10 */
+	pushq   %r11		/* pt_regs->r11 */
+	xorq    %r11, %r11	/* nospec   r11*/
+	pushq	%rbx		/* pt_regs->rbx */
+	xorl    %ebx, %ebx	/* nospec   rbx*/
+	pushq	%rbp		/* pt_regs->rbp */
+	xorl    %ebp, %ebp	/* nospec   rbp*/
+	pushq	%r12		/* pt_regs->r12 */
+	xorq    %r12, %r12	/* nospec   r12*/
+	pushq	%r13		/* pt_regs->r13 */
+	xorq    %r13, %r13	/* nospec   r13*/
+	pushq	%r14		/* pt_regs->r14 */
+	xorq    %r14, %r14	/* nospec   r14*/
+	pushq	%r15		/* pt_regs->r15 */
+	xorq    %r15, %r15	/* nospec   r15*/
+	UNWIND_HINT_REGS
+	.endm
+
 	.macro POP_REGS pop_rdi=1 skip_r11rcx=0
 	popq %r15
 	popq %r14
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 07692b4..cf4a9ae 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -564,8 +564,7 @@ END(irq_entries_start)
 	call	switch_to_thread_stack
 1:
 
-	ALLOC_PT_GPREGS_ON_STACK
-	SAVE_AND_CLEAR_REGS
+	PUSH_AND_CLEAR_REGS
 	ENCODE_FRAME_POINTER
 
 	testb	$3, CS(%rsp)
@@ -1112,8 +1111,7 @@ ENTRY(xen_failsafe_callback)
 	addq	$0x30, %rsp
 	UNWIND_HINT_IRET_REGS
 	pushq	$-1 /* orig_ax = -1 => not a system call */
-	ALLOC_PT_GPREGS_ON_STACK
-	SAVE_AND_CLEAR_REGS
+	PUSH_AND_CLEAR_REGS
 	ENCODE_FRAME_POINTER
 	jmp	error_exit
 END(xen_failsafe_callback)

  reply	other threads:[~2018-02-12 10:18 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-11 10:49 [PATCH v3 0/7] x86/entry: simplify and unify SAVE/POP_REGS Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 1/7] x86/entry: merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions Dominik Brodowski
2018-02-12 10:15   ` [tip:x86/pti] x86/entry/64: Merge " tip-bot for Dominik Brodowski
2018-02-13  9:00   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 2/7] x86/entry: merge POP_C_REGS and POP_EXTRA_REGS Dominik Brodowski
2018-02-12 10:16   ` [tip:x86/pti] x86/entry/64: Merge the POP_C_REGS and POP_EXTRA_REGS macros into a single POP_REGS macro tip-bot for Dominik Brodowski
2018-02-13  9:01   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 3/7] x86/entry: interleave XOR register clearing with PUSH instructions Dominik Brodowski
2018-02-12 10:16   ` [tip:x86/pti] x86/entry/64: Interleave " tip-bot for Dominik Brodowski
2018-02-13  9:01   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 4/7] x86/entry: introduce PUSH_AND_CLEAN_REGS Dominik Brodowski
2018-02-12 10:17   ` tip-bot for Dominik Brodowski [this message]
2018-02-12 13:29     ` [tip:x86/pti] x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro Denys Vlasenko
2018-02-12 13:36       ` David Laight
2018-02-12 13:43         ` Denys Vlasenko
2018-02-12 16:51       ` Linus Torvalds
2018-02-13  9:01   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 5/7] x86/entry: use PUSH_AND_CLEAN_REGS in more cases Dominik Brodowski
2018-02-12 10:17   ` [tip:x86/pti] x86/entry/64: Use " tip-bot for Dominik Brodowski
2018-02-13  9:02   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 6/7] x86/entry: get rid of ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS Dominik Brodowski
2018-02-12 10:18   ` [tip:x86/pti] x86/entry/64: Get rid of the ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS macros tip-bot for Dominik Brodowski
2018-02-13  9:02   ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 7/7] x86/entry: indent PUSH_AND_CLEAR_REGS and POP_REGS properly Dominik Brodowski
2018-02-12 10:18   ` [tip:x86/pti] x86/entry/64: Indent " tip-bot for Dominik Brodowski
2018-02-12 20:13     ` [PATCH] x86/entry/64: Remove unused icebp macro Borislav Petkov
2018-02-13  7:36       ` Ingo Molnar
2018-02-13  9:04       ` [tip:x86/pti] x86/entry/64: Remove the unused 'icebp' macro tip-bot for Borislav Petkov
2018-02-13  9:03   ` [tip:x86/pti] x86/entry/64: Indent PUSH_AND_CLEAR_REGS and POP_REGS properly tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 8/7] TESTING_ONLY x86/entry: reduce static footprint of idtentry Dominik Brodowski
2018-02-12  9:37   ` Ingo Molnar
2018-02-12 19:17     ` Linus Torvalds
2018-02-13 12:41       ` Ingo Molnar

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