From c89eb7d54c9762353295adae529d155723ce6c21 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Wed, 2 May 2018 11:03:32 -0700 Subject: [PATCH] FROMLIST: arm64: preserve x18 when CPU is suspended Don't lose the current task's shadow stack when the CPU is suspended. Bug: 145210207 Change-Id: I8f74f33b4b2c707e25e46bea4fb8a8f5ea1a7036 (am from https://lore.kernel.org/patchwork/patch/1149059/) Reviewed-by: Nick Desaulniers Reviewed-by: Kees Cook Reviewed-by: Mark Rutland Signed-off-by: Sami Tolvanen --- arch/arm64/include/asm/suspend.h | 2 +- arch/arm64/mm/proc.S | 14 ++++++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h index 8939c87c4dce..0cde2f473971 100644 --- a/arch/arm64/include/asm/suspend.h +++ b/arch/arm64/include/asm/suspend.h @@ -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 /* diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 7f0a622f8964..118597813da7 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -65,6 +65,8 @@ ENDPROC(cpu_do_idle) * 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 . */ ENTRY(cpu_do_suspend) mrs x2, tpidr_el0 @@ -89,6 +91,11 @@ 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 ENDPROC(cpu_do_suspend) @@ -105,6 +112,13 @@ ENTRY(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