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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: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Sami Tolvanen 2020-04-27 09:00:12 -07:00 committed by Will Deacon
parent da64e9d1f8
commit 6d37d81f44
2 changed files with 15 additions and 1 deletions
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2
arch/arm64/include/asm/suspend.h
View File

@ -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
/*

14
arch/arm64/mm/proc.S
View File

@ -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