[PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 46c3b93..5060d2d 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h

@@ -75,6 +75,7 @@ struct thread_info {
  *  TIF_SYSCALL_TRACE	- syscall trace active
  *  TIF_SYSCALL_TRACEPOINT - syscall tracepoint for ftrace
  *  TIF_SYSCALL_AUDIT	- syscall auditing
+ *  TIF_SYSCALL_EMU	- syscall emulation active
  *  TIF_SECOMP		- syscall secure computing
  *  TIF_SIGPENDING	- signal pending
  *  TIF_NEED_RESCHED	- rescheduling necessary

@@ -91,6 +92,7 @@ struct thread_info {
 #define TIF_SYSCALL_AUDIT	9
 #define TIF_SYSCALL_TRACEPOINT	10
 #define TIF_SECCOMP		11
+#define TIF_SYSCALL_EMU		12
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 #define TIF_FREEZE		19
 #define TIF_RESTORE_SIGMASK	20

@@ -106,6 +108,7 @@ struct thread_info {
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_SYSCALL_EMU	(1 << TIF_SYSCALL_EMU)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_32BIT		(1 << TIF_32BIT)
 

@@ -115,7 +118,7 @@ struct thread_info {
 
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
-				 _TIF_NOHZ)
+				 _TIF_NOHZ | _TIF_SYSCALL_EMU)
 
 #endif /* __KERNEL__ */
 #endif /* __ASM_THREAD_INFO_H */

diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
index b5c3933..04ab06f 100644
--- a/arch/arm64/include/uapi/asm/ptrace.h
+++ b/arch/arm64/include/uapi/asm/ptrace.h

@@ -23,6 +23,8 @@
 
 #include <asm/hwcap.h>
 
+#define PTRACE_SYSEMU			31
+#define PTRACE_SYSEMU_SINGLESTEP	32
 
 /*
  * PSR bits

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index fc35e06..ff3e322 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c

@@ -165,6 +165,9 @@ void ptrace_disable(struct task_struct *child)
 	 * is likely to cause regressions on obscure architectures.
 	 */
 	user_disable_single_step(child);
+#ifdef TIF_SYSCALL_EMU
+	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+#endif
 }
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT

@@ -1351,6 +1354,11 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs)
 	if (test_thread_flag(TIF_SYSCALL_TRACE))
 		tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
 
+	if (test_thread_flag(TIF_SYSCALL_EMU)) {
+		tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
+		return -1;
+	}

+
 	/* Do the secure computing after ptrace; failures should be fast. */
 	if (secure_computing(NULL) == -1)
 		return -1;

@@ -1373,6 +1381,15 @@ asmlinkage void syscall_trace_exit(struct pt_regs *regs)
 
 	if (test_thread_flag(TIF_SYSCALL_TRACE))
 		tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT);
+
+	/*
+	 * We only get here because of TIF_SINGLESTEP,
+	 * for PTRACE_SYSEMU_SINGLESTEP, we already reported
+	 * the syscall instruction in syscall_trace_enter().
+	 */
+	if (test_thread_flag(TIF_SINGLESTEP) &&
+			!test_thread_flag(TIF_SYSCALL_EMU))
+		tracehook_report_syscall_exit(regs, 1);
 }
 
 /*

-- 
2.7.4