[PATCH v2 6/6] arm64: ptrace: add support for syscall emulation

[Sudeep Holla]

Add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support on arm64.
We can just make sure of the generic ptrace_syscall_enter hook to
support PTRACE_SYSEMU. We don't need any special handling for
PTRACE_SYSEMU_SINGLESTEP.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
---
 arch/arm64/include/asm/thread_info.h | 5 ++++-
 arch/arm64/kernel/ptrace.c           | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index eb3ef73e07cf..c285d1ce7186 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -75,6 +75,7 @@ void arch_release_task_struct(struct task_struct *tsk);
  *  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 @@ void arch_release_task_struct(struct task_struct *tsk);
 #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
@@ -109,6 +111,7 @@ void arch_release_task_struct(struct task_struct *tsk);
 #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_FSCHECK		(1 << TIF_FSCHECK)
 #define _TIF_32BIT		(1 << TIF_32BIT)
@@ -120,7 +123,7 @@ void arch_release_task_struct(struct task_struct *tsk);
 
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
-				 _TIF_NOHZ)
+				 _TIF_NOHZ | _TIF_SYSCALL_EMU)
 
 #define INIT_THREAD_INFO(tsk)						\
 {									\
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index b82e0a9b3da3..cf29275cd4d9 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1819,6 +1819,9 @@ static void tracehook_report_syscall(struct pt_regs *regs,
 
 int syscall_trace_enter(struct pt_regs *regs)
 {
+	if (unlikely(ptrace_syscall_enter(regs)))
+		return -1;
+
 	if (test_thread_flag(TIF_SYSCALL_TRACE))
 		tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
 
-- 
2.17.1