[RFC 10/10] arm64: Enable reclaimable stacks

[David Stevens <stevensd@google.com>]

Implement top_of_blocked_task_stack() to get the stack pointer out of
a thread_struct and enable HAVE_ARCH_RECLAIMABLE_STACK.

Signed-off-by: David Stevens <stevensd@google.com>
---
 arch/arm64/Kconfig                 | 1 +
 arch/arm64/include/asm/processor.h | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b3afe0688919..262a4fddce19 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -173,6 +173,7 @@ config ARM64
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select HAVE_ARCH_VMAP_STACK
+	select HAVE_ARCH_RECLAIMABLE_STACK
 	select HAVE_ARM_SMCCC
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_EBPF_JIT
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index c2a627f39314..f5a550835c94 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -204,6 +204,11 @@ struct thread_struct {
 #endif
 };
 
+static inline unsigned long top_of_blocked_task_stack(struct thread_struct *thread)
+{
+	return thread->cpu_context.sp;
+}
+
 static inline unsigned int thread_get_vl(struct thread_struct *thread,
 					 enum vec_type type)
 {
-- 
2.55.0.897.gb25b4bd76c-goog