Commit 6d37d81f authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Will Deacon
Browse files

arm64: Preserve register x18 when CPU is suspended 



Don't lose the current task's shadow stack when the CPU is suspended.

Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent da64e9d1

arch/arm64/include/asm/suspend.h

+1 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 
#ifndef __ASM_SUSPEND_H

#define __ASM_SUSPEND_H



#define NR_CTX_REGS 12

#define NR_CTX_REGS 13

#define NR_CALLEE_SAVED_REGS 12



/*

arch/arm64/mm/proc.S

+14 −0
Original line number Diff line number Diff line
@@ -58,6 +58,8 @@ 
 * cpu_do_suspend - save CPU registers context

 *

 * x0: virtual address of context pointer

 *

 * This must be kept in sync with struct cpu_suspend_ctx in <asm/suspend.h>.

 */

SYM_FUNC_START(cpu_do_suspend)

	mrs	x2, tpidr_el0
@@ -82,6 +84,11 @@ alternative_endif 
	stp	x8, x9, [x0, #48]

	stp	x10, x11, [x0, #64]

	stp	x12, x13, [x0, #80]

	/*

	 * Save x18 as it may be used as a platform register, e.g. by shadow

	 * call stack.

	 */

	str	x18, [x0, #96]

	ret

SYM_FUNC_END(cpu_do_suspend)
@@ -98,6 +105,13 @@ SYM_FUNC_START(cpu_do_resume) 
	ldp	x9, x10, [x0, #48]

	ldp	x11, x12, [x0, #64]

	ldp	x13, x14, [x0, #80]

	/*

	 * Restore x18, as it may be used as a platform register, and clear

	 * the buffer to minimize the risk of exposure when used for shadow

	 * call stack.

	 */

	ldr	x18, [x0, #96]

	str	xzr, [x0, #96]

	msr	tpidr_el0, x2

	msr	tpidrro_el0, x3

	msr	contextidr_el1, x4