[PATCH v8 08/12] arm64/ptrace: Use syscall_get_arguments() heleper

[Jinjie Ruan]

The generic entry check audit context first and use
syscall_get_arguments() helper.

In order to switch to the generic entry for arm64,

- Also use syscall_get_arguments() to get audit_syscall_entry()'s
  last four parameters.

- Extract the syscall_enter_audit() helper to make it clear.

- Check audit context first, which saves an unnecessary memcpy when
  current process's audit_context is NULL.

Overall these changes make syscall_enter_audit() exactly equivalent
to the generic one.

No functional changes.

Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
---
 arch/arm64/kernel/ptrace.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 72d4d987ba3b..c2bd0130212d 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2381,6 +2381,16 @@ static void report_syscall_exit(struct pt_regs *regs)
 	}
 }
 
+static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
+{
+	if (unlikely(audit_context())) {
+		unsigned long args[6];
+
+		syscall_get_arguments(current, regs, args);
+		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
+	}
+}
+
 int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 {
 	int ret;
@@ -2411,8 +2421,7 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 		 syscall = syscall_get_nr(current, regs);
 	}
 
-	audit_syscall_entry(syscall, regs->orig_x0, regs->regs[1],
-			    regs->regs[2], regs->regs[3]);
+	syscall_enter_audit(regs, syscall);
 
 	return ret ? : syscall;
 }
-- 
2.34.1