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

From: [email-masked] (Haibo.Xu)
Date: Mon, 3 Sep 2018 14:23:17 +0800

Add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support on ARM64.
This copies the x86 semantics for invoking ptrace hooks, and have
been verified on ARM64 machine.

Signed-off-by: Haibo.Xu <[email-masked]>
Signed-off-by: Bin.Lu <[email-masked]>
---
 arch/arm64/include/asm/thread_info.h |  5 ++++-
 arch/arm64/include/uapi/asm/ptrace.h |  2 ++
 arch/arm64/kernel/ptrace.c           | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

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

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