[PATCH -next v5 20/22] entry: Add arch_ptrace_report_syscall_entry/exit()

[Jinjie Ruan <ruanjinjie@xxxxxxxxxx>]

Due to historical reasons, ARM64 need to save/restore during syscall
entry/exit because ARM64 use a scratch register (ip(r12) on AArch32,
x7 on AArch64) to denote syscall entry/exit, which differs from
the implementation of the generic entry.

Add arch_ptrace_report_syscall_entry/exit() as the default
ptrace_report_syscall_entry/exit() implementation. This allows arm64
to implement the architecture specific version for switching over to
the generic entry code.

Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Suggested-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 kernel/entry/syscall-common.c | 43 +++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/kernel/entry/syscall-common.c b/kernel/entry/syscall-common.c
index f78285097111..9ffa6349e769 100644
--- a/kernel/entry/syscall-common.c
+++ b/kernel/entry/syscall-common.c
@@ -17,6 +17,25 @@ static inline void syscall_enter_audit(struct pt_regs *regs, 
long syscall)
        }
 }
 
+/**
+ * arch_ptrace_report_syscall_entry - Architecture specific
+ *                                   ptrace_report_syscall_entry().
+ *
+ * Invoked from syscall_trace_enter() to wrap ptrace_report_syscall_entry().
+ * Defaults to ptrace_report_syscall_entry.
+ *
+ * The main purpose is to support arch-specific ptrace_report_syscall_entry()
+ * implementation.
+ */
+static inline int arch_ptrace_report_syscall_entry(struct pt_regs *regs);
+
+#ifndef arch_ptrace_report_syscall_entry
+static inline int arch_ptrace_report_syscall_entry(struct pt_regs *regs)
+{
+       return ptrace_report_syscall_entry(regs);
+}
+#endif
+
 long syscall_trace_enter(struct pt_regs *regs, long syscall,
                                unsigned long work)
 {
@@ -34,7 +53,7 @@ long syscall_trace_enter(struct pt_regs *regs, long syscall,
 
        /* Handle ptrace */
        if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
-               ret = ptrace_report_syscall_entry(regs);
+               ret = arch_ptrace_report_syscall_entry(regs);
                if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
                        return -1L;
        }
@@ -84,6 +103,26 @@ static inline bool report_single_step(unsigned long work)
        return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
 }
 
+/**
+ * arch_ptrace_report_syscall_exit - Architecture specific
+ *                                  ptrace_report_syscall_exit.
+ *
+ * Invoked from syscall_exit_work() to wrap ptrace_report_syscall_exit().
+ *
+ * The main purpose is to support arch-specific ptrace_report_syscall_exit
+ * implementation.
+ */
+static inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs,
+                                                  int step);
+
+#ifndef arch_ptrace_report_syscall_exit
+static inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs,
+                                                  int step)
+{
+       ptrace_report_syscall_exit(regs, step);
+}
+#endif
+
 static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
 {
        bool step;
@@ -108,7 +147,7 @@ static void syscall_exit_work(struct pt_regs *regs, 
unsigned long work)
 
        step = report_single_step(work);
        if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
-               ptrace_report_syscall_exit(regs, step);
+               arch_ptrace_report_syscall_exit(regs, step);
 }
 
 /*
-- 
2.34.1