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

["Haibo Xu (Arm Technology China)" <Haibo.Xu@arm.com>]

On 2019/3/18 18:49, Sudeep Holla wrote:
> 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.

This looks good to me. But it'd be better to add the same logic to handle
PTRACE_SYSEMU_SINGLESTEP as that of x86 in case we may need enable the single
step trace function in the future.

>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  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_AUDIT9
>  #define TIF_SYSCALL_TRACEPOINT10
>  #define TIF_SECCOMP11
> +#define TIF_SYSCALL_EMU12
>  #define TIF_MEMDIE18/* is terminating due to OOM killer */
>  #define TIF_FREEZE19
>  #define TIF_RESTORE_SIGMASK20
> @@ -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);
>
>
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