Commit 30907fd1 authored by Dominik Brodowski's avatar Dominik Brodowski Committed by Ingo Molnar
Browse files

x86/entry/64: Use PUSH_AND_CLEAN_REGS in more cases 



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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarDominik 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/20180211104949.12992-6-linux@dominikbrodowski.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3f01daec

arch/x86/entry/calling.h

+3 −3
Original line number Diff line number Diff line
@@ -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 */

arch/x86/entry/entry_64.S

+3 −62
Original line number Diff line number Diff line
@@ -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



	/*

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