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Subject[PATCH v4 13/17] arm64: preserve x18 when CPU is suspended
From
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>
---
arch/arm64/include/asm/suspend.h | 2 +-
arch/arm64/mm/proc.S | 10 ++++++++++
2 files changed, 11 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 fdabf40a83c8..5616dc52a033 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -49,6 +49,8 @@
* 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>.
*/
ENTRY(cpu_do_suspend)
mrs x2, tpidr_el0
@@ -73,6 +75,9 @@ alternative_endif
stp x8, x9, [x0, #48]
stp x10, x11, [x0, #64]
stp x12, x13, [x0, #80]
+#ifdef CONFIG_SHADOW_CALL_STACK
+ str x18, [x0, #96]
+#endif
ret
ENDPROC(cpu_do_suspend)

@@ -89,6 +94,11 @@ ENTRY(cpu_do_resume)
ldp x9, x10, [x0, #48]
ldp x11, x12, [x0, #64]
ldp x13, x14, [x0, #80]
+#ifdef CONFIG_SHADOW_CALL_STACK
+ ldr x18, [x0, #96]
+ /* Clear the SCS pointer from the state buffer */
+ str xzr, [x0, #96]
+#endif
msr tpidr_el0, x2
msr tpidrro_el0, x3
msr contextidr_el1, x4
--
2.24.0.rc1.363.gb1bccd3e3d-goog
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