arm64: ptrace: add support for syscall emulation

Add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support on arm64.
We don't need any special handling for PTRACE_SYSEMU_SINGLESTEP.

It's quite difficult to generalize handling PTRACE_SYSEMU cross
architectures and avoid calls to tracehook_report_syscall_entry twice.
Different architecture have different mechanism to indicate NO_SYSCALL
and trying to generalise adds more code for no gain.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index eb3ef73..c285d1c 100644 (file)
--- 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 b82e0a9..9353355 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1819,8 +1819,12 @@ static void tracehook_report_syscall(struct pt_regs *regs,
 
 int syscall_trace_enter(struct pt_regs *regs)
 {
-       if (test_thread_flag(TIF_SYSCALL_TRACE))
+       if (test_thread_flag(TIF_SYSCALL_TRACE) ||
+               test_thread_flag(TIF_SYSCALL_EMU)) {
                tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
+               if (!in_syscall(regs) || test_thread_flag(TIF_SYSCALL_EMU))
+                       return -1;
+       }
 
        /* Do the secure computing after ptrace; failures should be fast. */
        if (secure_computing(NULL) == -1)