From: Dominik Brodowski <linux@dominikbrodowski.net>
To: linux-kernel@vger.kernel.org, mingo@kernel.org, x86@kernel.org
Cc: dan.j.williams@intel.com, tglx@linutronix.de, ak@linux.intel.com,
torvalds@linux-foundation.org, luto@kernel.org
Subject: [RFC v2 PATCH 5/7] x86/entry: use PUSH_AND_CLEAN_REGS in more cases
Date: Wed, 7 Feb 2018 21:15:15 +0100 [thread overview]
Message-ID: <20180207201517.6518-6-linux@dominikbrodowski.net> (raw)
In-Reply-To: <20180207201517.6518-1-linux@dominikbrodowski.net>
entry_SYSCALL_64_after_hwframe and nmi can be converted to use
PUSH_AND_CLEAN_REGS instead of opencoded variants thereof. Due to
the interleaving, the additional XOR-based clearing of r8 and r9
in entry_SYSCALL_64_after_hwframe should not have any noticeable
negative implications.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
---
arch/x86/entry/calling.h | 6 ++---
arch/x86/entry/entry_64.S | 65 +++--------------------------------------------
2 files changed, 6 insertions(+), 65 deletions(-)
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 57b1b87a04f0..d6a97e2945ee 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -137,7 +137,7 @@ For 32-bit we have the following conventions - kernel is built with
UNWIND_HINT_REGS offset=\offset
.endm
- .macro PUSH_AND_CLEAR_REGS
+ .macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax
/*
* Push registers and sanitize registers of values that a
* speculation attack might otherwise want to exploit. The
@@ -147,9 +147,9 @@ For 32-bit we have the following conventions - kernel is built with
*/
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
- pushq %rdx /* pt_regs->dx */
+ pushq \rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
- pushq %rax /* pt_regs->ax */
+ pushq \rax /* pt_regs->ax */
pushq %r8 /* pt_regs->r8 */
xorq %r8, %r8 /* nospec r8 */
pushq %r9 /* pt_regs->r9 */
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9dd3fbfdc75d..9c4fe360db42 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -227,35 +227,8 @@ ENTRY(entry_SYSCALL_64)
pushq %rcx /* pt_regs->ip */
GLOBAL(entry_SYSCALL_64_after_hwframe)
pushq %rax /* pt_regs->orig_ax */
- pushq %rdi /* pt_regs->di */
- pushq %rsi /* pt_regs->si */
- pushq %rdx /* pt_regs->dx */
- pushq %rcx /* pt_regs->cx */
- pushq $-ENOSYS /* pt_regs->ax */
- pushq %r8 /* pt_regs->r8 */
- pushq %r9 /* pt_regs->r9 */
- pushq %r10 /* pt_regs->r10 */
- /*
- * Clear extra registers that a speculation attack might
- * otherwise want to exploit. Interleave XOR with PUSH
- * for better uop scheduling:
- */
- xorq %r10, %r10 /* nospec r10 */
- pushq %r11 /* pt_regs->r11 */
- xorq %r11, %r11 /* nospec r11 */
- pushq %rbx /* pt_regs->rbx */
- xorl %ebx, %ebx /* nospec rbx */
- pushq %rbp /* pt_regs->rbp */
- xorl %ebp, %ebp /* nospec rbp */
- pushq %r12 /* pt_regs->r12 */
- xorq %r12, %r12 /* nospec r12 */
- pushq %r13 /* pt_regs->r13 */
- xorq %r13, %r13 /* nospec r13 */
- pushq %r14 /* pt_regs->r14 */
- xorq %r14, %r14 /* nospec r14 */
- pushq %r15 /* pt_regs->r15 */
- xorq %r15, %r15 /* nospec r15 */
- UNWIND_HINT_REGS
+
+ PUSH_AND_CLEAR_REGS rax=$-ENOSYS
TRACE_IRQS_OFF
@@ -1388,39 +1361,7 @@ ENTRY(nmi)
pushq 1*8(%rdx) /* pt_regs->rip */
UNWIND_HINT_IRET_REGS
pushq $-1 /* pt_regs->orig_ax */
- 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 */
- /*
- * 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 %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
+ PUSH_AND_CLEAR_REGS rdx=(%rdx)
ENCODE_FRAME_POINTER
/*
--
2.16.1
next prev parent reply other threads:[~2018-02-07 20:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-07 20:15 [RFC v2 PATCH 0/7] x86/entry: simplify and unify SAVE/POP_REGS Dominik Brodowski
2018-02-07 20:15 ` [RFC v2 PATCH 1/7] x86/entry: merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions Dominik Brodowski
2018-02-07 20:15 ` [RFC v2 PATCH 2/7] x86/entry: merge POP_C_REGS and POP_EXTRA_REGS Dominik Brodowski
2018-02-07 20:15 ` [RFC v2 PATCH 3/7] x86/entry: interleave XOR register clearing with PUSH instructions Dominik Brodowski
2018-02-07 20:15 ` [RFC v2 PATCH 4/7] x86/entry: introduce PUSH_AND_CLEAN_REGS Dominik Brodowski
2018-02-07 20:15 ` Dominik Brodowski [this message]
2018-02-07 20:15 ` [RFC v2 PATCH 6/7] x86/entry: get rid of ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS Dominik Brodowski
2018-02-07 20:44 ` Linus Torvalds
2018-02-07 21:29 ` Dominik Brodowski
2018-02-07 21:58 ` Linus Torvalds
2018-02-08 7:20 ` Dominik Brodowski
2018-02-08 9:47 ` Ingo Molnar
2018-02-08 17:39 ` Linus Torvalds
2018-02-08 18:35 ` Josh Poimboeuf
2018-02-07 20:15 ` [RFC v2 PATCH 7/7] x86/entry: indent PUSH_AND_CLEAR_REGS and POP_REGS properly Dominik Brodowski
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