Add some arch functions to support arm64 to use generic entry, which do not
affect existing architectures that use generic entry:

 - arch_prepare/post_report_syscall_entry/exit().

 - arch_enter_from_kernel_mode(), arch_exit_to_kernel_mode_prepare().

 - arch_irqentry_exit_need_resched() to support architecture-related
   need_resched() check logic.

Also make syscall_exit_work() not static and move report_single_step() to
thread_info.h, which can be used by arm64 later.

x86 and Riscv compilation test ok after this patch.

Signed-off-by: Jinjie Ruan <redacted>
Suggested-by: Thomas Gleixner <redacted>
---
v3:
- Make the arch funcs not use __weak as Thomas suggested.
- Make arch_forget_syscall() folded in arch_post_report_syscall_entry().
- __always_inline -> inline.
- Move report_single_step() to thread_info.h for arm64
- Add Suggested-by.
- Update the commit message.

v2:
- Fix a bug that not call arch_post_report_syscall_entry() in
  syscall_trace_enter() if ptrace_report_syscall_entry() return not zero.
- Update the commit message.
---
 include/linux/entry-common.h | 90 ++++++++++++++++++++++++++++++++++++
 include/linux/thread_info.h  | 13 ++++++
 kernel/entry/common.c        | 37 +++++++--------
 3 files changed, 122 insertions(+), 18 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index b0fb775a600d..2aea23ca9d66 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h

@@ -290,6 +290,94 @@ static __always_inline void arch_exit_to_user_mode(void);
 static __always_inline void arch_exit_to_user_mode(void) { }
 #endif
 
+/**
+ * arch_enter_from_kernel_mode - Architecture specific check work.

+
 /**
  * arch_do_signal_or_restart -  Architecture specific signal delivery function
  * @regs:	Pointer to currents pt_regs

@@ -552,4 +640,6 @@ irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
  */
 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
 
+void syscall_exit_work(struct pt_regs *regs, unsigned long work);
+
 #endif

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 9ea0b28068f4..062de9666ef3 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h

@@ -55,6 +55,19 @@ enum syscall_work_bit {
 #define SYSCALL_WORK_SYSCALL_AUDIT	BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)
 #define SYSCALL_WORK_SYSCALL_USER_DISPATCH BIT(SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH)
 #define SYSCALL_WORK_SYSCALL_EXIT_TRAP	BIT(SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP)
+
+/*
+ * If SYSCALL_EMU is set, then the only reason to report is when
+ * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
+ * instruction has been already reported in syscall_enter_from_user_mode().
+ */
+static inline bool report_single_step(unsigned long work)
+{
+	if (work & SYSCALL_WORK_SYSCALL_EMU)
+		return false;
+
+	return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
+}
 #endif
 
 #include <asm/thread_info.h>

diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 90843cc38588..cd76391ffcb9 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c

@@ -28,6 +28,7 @@ static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
 long syscall_trace_enter(struct pt_regs *regs, long syscall,
 				unsigned long work)
 {
+	unsigned long saved_reg;

 	long ret = 0;
 
 	/*

@@ -42,8 +43,10 @@ long syscall_trace_enter(struct pt_regs *regs, long syscall,
 
 	/* Handle ptrace */
 	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
+		saved_reg = arch_prepare_report_syscall_entry(regs);
 		ret = ptrace_report_syscall_entry(regs);
-		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
+		arch_post_report_syscall_entry(regs, saved_reg, ret);
+		if (ret || work & SYSCALL_WORK_SYSCALL_EMU)
 			return -1L;
 	}
 

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