Re: [PATCH v9 02/16] arm64/ptrace: Split report_syscall()

[Anshuman Khandual]

On 04/12/25 1:51 PM, Jinjie Ruan wrote:
> The generic syscall entry code has the form:
> 
> | syscall_trace_enter()
> | {
> |     ptrace_report_syscall_entry()
> | }
> |
> | syscall_exit_work()
> | {
> |     ptrace_report_syscall_exit()
> | }
> 
> In preparation for moving arm64 over to the generic entry code, split
> report_syscall() to two separate enter and exit functions to align
> the structure of the arm64 code with syscall_trace_enter() and
> syscall_exit_work() from the generic entry code.
> 
> No functional changes.
> 
> Reviewed-by: Kevin Brodsky <kevin.brod...@arm.com>
> Suggested-by: Mark Rutland <mark.rutl...@arm.com>
> Signed-off-by: Jinjie Ruan <ruanjin...@huawei.com>

LGTM.

Reviewed-by: Anshuman Khandual <anshuman.khand...@arm.com>

> ---
> v8:
> - report_syscall_enter() -> report_syscall_entry().
> - Add ptrace_save_reg() helper.
> ---
>  arch/arm64/kernel/ptrace.c | 41 +++++++++++++++++++++++++++-----------
>  1 file changed, 29 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 4b001121c72d..4532e9831856 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -2317,9 +2317,10 @@ enum ptrace_syscall_dir {
>       PTRACE_SYSCALL_EXIT,
>  };
>  
> -static void report_syscall(struct pt_regs *regs, enum ptrace_syscall_dir dir)
> +static __always_inline unsigned long ptrace_save_reg(struct pt_regs *regs,
> +                                                  enum ptrace_syscall_dir 
> dir,
> +                                                  int *regno)
>  {
> -     int regno;
>       unsigned long saved_reg;
>  
>       /*
> @@ -2338,15 +2339,31 @@ static void report_syscall(struct pt_regs *regs, enum 
> ptrace_syscall_dir dir)
>        * - Syscall stops behave differently to seccomp and pseudo-step traps
>        *   (the latter do not nobble any registers).
>        */
> -     regno = (is_compat_task() ? 12 : 7);
> -     saved_reg = regs->regs[regno];
> -     regs->regs[regno] = dir;
> +     *regno = (is_compat_task() ? 12 : 7);
> +     saved_reg = regs->regs[*regno];
> +     regs->regs[*regno] = dir;
>  
> -     if (dir == PTRACE_SYSCALL_ENTER) {
> -             if (ptrace_report_syscall_entry(regs))
> -                     forget_syscall(regs);
> -             regs->regs[regno] = saved_reg;
> -     } else if (!test_thread_flag(TIF_SINGLESTEP)) {
> +     return saved_reg;
> +}
> +
> +static void report_syscall_entry(struct pt_regs *regs)
> +{
> +     unsigned long saved_reg;
> +     int regno;
> +
> +     saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
> +     if (ptrace_report_syscall_entry(regs))
> +             forget_syscall(regs);
> +     regs->regs[regno] = saved_reg;
> +}
> +
> +static void report_syscall_exit(struct pt_regs *regs)
> +{
> +     unsigned long saved_reg;
> +     int regno;
> +
> +     saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_EXIT, &regno);
> +     if (!test_thread_flag(TIF_SINGLESTEP)) {
>               ptrace_report_syscall_exit(regs, 0);
>               regs->regs[regno] = saved_reg;
>       } else {
> @@ -2366,7 +2383,7 @@ int syscall_trace_enter(struct pt_regs *regs)
>       unsigned long flags = read_thread_flags();
>  
>       if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
> -             report_syscall(regs, PTRACE_SYSCALL_ENTER);
> +             report_syscall_entry(regs);
>               if (flags & _TIF_SYSCALL_EMU)
>                       return NO_SYSCALL;
>       }
> @@ -2394,7 +2411,7 @@ void syscall_trace_exit(struct pt_regs *regs)
>               trace_sys_exit(regs, syscall_get_return_value(current, regs));
>  
>       if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
> -             report_syscall(regs, PTRACE_SYSCALL_EXIT);
> +             report_syscall_exit(regs);
>  
>       rseq_syscall(regs);
>  }