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x86/entry/64: Interleave XOR register clearing with PUSH instructions

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Same as is done for syscalls, interleave XOR with PUSH instructions
for exceptions/interrupts, in order to minimize the cost of the
additional instructions required for register clearing.

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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Link: http://lkml.kernel.org/r/20180211104949.12992-4-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dominik Brodowski
2018-02-11 11:49:44 +01:00
committed by Ingo Molnar
parent 502af0d708
commit f7bafa2b05
2 changed files with 40 additions and 30 deletions
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40
arch/x86/entry/calling.h
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@@ -101,44 +101,42 @@ For 32-bit we have the following conventions - kernel is built with
addq $-(15*8), %rsp
.endm
.macro SAVE_REGS offset=0
.macro SAVE_AND_CLEAR_REGS offset=0
/*
* Save 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:
*/
movq %rdi, 14*8+\offset(%rsp)
movq %rsi, 13*8+\offset(%rsp)
movq %rdx, 12*8+\offset(%rsp)
movq %rcx, 11*8+\offset(%rsp)
movq %rax, 10*8+\offset(%rsp)
movq %r8, 9*8+\offset(%rsp)
xorq %r8, %r8 /* nospec r8 */
movq %r9, 8*8+\offset(%rsp)
xorq %r9, %r9 /* nospec r9 */
movq %r10, 7*8+\offset(%rsp)
xorq %r10, %r10 /* nospec r10 */
movq %r11, 6*8+\offset(%rsp)
xorq %r11, %r11 /* nospec r11 */
movq %rbx, 5*8+\offset(%rsp)
xorl %ebx, %ebx /* nospec rbx */
movq %rbp, 4*8+\offset(%rsp)
xorl %ebp, %ebp /* nospec rbp */
movq %r12, 3*8+\offset(%rsp)
xorq %r12, %r12 /* nospec r12 */
movq %r13, 2*8+\offset(%rsp)
xorq %r13, %r13 /* nospec r13 */
movq %r14, 1*8+\offset(%rsp)
xorq %r14, %r14 /* nospec r14 */
movq %r15, 0*8+\offset(%rsp)
xorq %r15, %r15 /* nospec r15 */
UNWIND_HINT_REGS offset=\offset
.endm
/*
* 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:
*/
.macro CLEAR_REGS_NOSPEC
xorl %ebp, %ebp
xorl %ebx, %ebx
xorq %r8, %r8
xorq %r9, %r9
xorq %r10, %r10
xorq %r11, %r11
xorq %r12, %r12
xorq %r13, %r13
xorq %r14, %r14
xorq %r15, %r15
.endm
.macro POP_REGS pop_rdi=1 skip_r11rcx=0
popq %r15
popq %r14
@@ -177,7 +175,7 @@ For 32-bit we have the following conventions - kernel is built with
* is just setting the LSB, which makes it an invalid stack address and is also
* a signal to the unwinder that it's a pt_regs pointer in disguise.
*
* NOTE: This macro must be used *after* SAVE_REGS because it corrupts
* NOTE: This macro must be used *after* SAVE_AND_CLEAR_REGS because it corrupts
* the original rbp.
*/
.macro ENCODE_FRAME_POINTER ptregs_offset=0