[RFC V2 2/8] powerpc: Prepare to build with generic entry/exit framework

[Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>]

Enabling build with generic entry/exit framework for powerpc
architecture requires few necessary steps.

Introducing minor infrastructure updates to prepare for future generic
framework handling:

- Add syscall_work field to struct thread_info for SYSCALL_WORK_* flags.
- Provide arch_syscall_is_vdso_sigreturn() stub, returning false.
- Add on_thread_stack() helper to test whether the current stack pointer
  lies within the task’s kernel stack.

No functional change is intended with this patch.

Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
---
 arch/powerpc/include/asm/entry-common.h | 11 +++++++++++
 arch/powerpc/include/asm/stacktrace.h   |  8 ++++++++
 arch/powerpc/include/asm/syscall.h      |  5 +++++
 arch/powerpc/include/asm/thread_info.h  |  1 +
 4 files changed, 25 insertions(+)
 create mode 100644 arch/powerpc/include/asm/entry-common.h

diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h
new file mode 100644
index 0000000000000..3af16d821d07e
--- /dev/null
+++ b/arch/powerpc/include/asm/entry-common.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_PPC_ENTRY_COMMON_H
+#define _ASM_PPC_ENTRY_COMMON_H
+
+#ifdef CONFIG_GENERIC_IRQ_ENTRY
+
+#include <asm/stacktrace.h>
+
+#endif /* CONFIG_GENERIC_IRQ_ENTRY */
+#endif /* _ASM_PPC_ENTRY_COMMON_H */
diff --git a/arch/powerpc/include/asm/stacktrace.h b/arch/powerpc/include/asm/stacktrace.h
index 6149b53b3bc8e..3f0a242468813 100644
--- a/arch/powerpc/include/asm/stacktrace.h
+++ b/arch/powerpc/include/asm/stacktrace.h
@@ -8,6 +8,14 @@
 #ifndef _ASM_POWERPC_STACKTRACE_H
 #define _ASM_POWERPC_STACKTRACE_H
 
+#include <linux/sched.h>
+
 void show_user_instructions(struct pt_regs *regs);
 
+static inline bool on_thread_stack(void)
+{
+	return !(((unsigned long)(current->stack) ^ current_stack_pointer)
+			& ~(THREAD_SIZE -1));
+}
+
 #endif /* _ASM_POWERPC_STACKTRACE_H */
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 4b3c52ed6e9d2..834fcc4f7b543 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -139,4 +139,9 @@ static inline int syscall_get_arch(struct task_struct *task)
 	else
 		return AUDIT_ARCH_PPC64;
 }
+
+static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
+{
+	return false;
+}
 #endif	/* _ASM_SYSCALL_H */
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 2785c7462ebf7..d0e87c9bae0b0 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -54,6 +54,7 @@
 struct thread_info {
 	int		preempt_count;		/* 0 => preemptable,
 						   <0 => BUG */
+	unsigned long	syscall_work;		/* SYSCALL_WORK_ flags */
 #ifdef CONFIG_SMP
 	unsigned int	cpu;
 #endif
-- 
2.51.0