[PATCH v3 2/8] powerpc: Prepare to build with generic entry/exit framework

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

From: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>

This patch introduces preparatory changes needed to support building
PowerPC with the generic entry/exit (irqentry) framework.

The following infrastructure updates are added:
 - Add a syscall_work field to struct thread_info to hold SYSCALL_WORK_* flags.
 - Provide a stub implementation of arch_syscall_is_vdso_sigreturn(),
   returning false for now.
 - Introduce on_thread_stack() helper to detect if the current stack pointer
   lies within the task’s kernel stack.

These additions enable later integration with the generic entry/exit
infrastructure while keeping existing PowerPC behavior unchanged.

No functional change is intended in this patch.

Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
---
 arch/powerpc/include/asm/entry-common.h | 8 ++++++++
 arch/powerpc/include/asm/stacktrace.h   | 6 ++++++
 arch/powerpc/include/asm/syscall.h      | 5 +++++
 arch/powerpc/include/asm/thread_info.h  | 1 +
 4 files changed, 20 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 000000000000..05ce0583b600
--- /dev/null
+++ b/arch/powerpc/include/asm/entry-common.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_PPC_ENTRY_COMMON_H
+#define _ASM_PPC_ENTRY_COMMON_H
+
+#include <asm/stacktrace.h>
+
+#endif /* _ASM_PPC_ENTRY_COMMON_H */
diff --git a/arch/powerpc/include/asm/stacktrace.h b/arch/powerpc/include/asm/stacktrace.h
index 6149b53b3bc8..987f2e996262 100644
--- a/arch/powerpc/include/asm/stacktrace.h
+++ b/arch/powerpc/include/asm/stacktrace.h
@@ -10,4 +10,10 @@
 
 void show_user_instructions(struct pt_regs *regs);
 
+static __always_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 4b3c52ed6e9d..834fcc4f7b54 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 b0f200aba2b3..9c8270354f0b 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -57,6 +57,7 @@ struct thread_info {
 #ifdef CONFIG_SMP
 	unsigned int	cpu;
 #endif
+	unsigned long	syscall_work;		/* SYSCALL_WORK_ flags */
 	unsigned long	local_flags;		/* private flags for thread */
 #ifdef CONFIG_LIVEPATCH_64
 	unsigned long *livepatch_sp;
-- 
2.52.0