Re: [PATCH v9 03/16] arm64/ptrace: Return early for ptrace_report_syscall_entry() error

[Anshuman Khandual]

On 04/12/25 1:51 PM, Jinjie Ruan wrote:
> The generic entry abort the syscall_trace_enter() sequence if
> ptrace_report_syscall_entry() errors out, but arm64 not.
> 
> As the ptrace_report_syscall_entry() comment said, the calling arch code
> should abort the system call and must prevent normal entry so no system
> call is made if ptrace_report_syscall_entry() return nonzero.
> 
> In preparation for moving arm64 over to the generic entry code,
> return early if ptrace_report_syscall_entry() encounters an error.
> 
> Signed-off-by: Jinjie Ruan <ruanjin...@huawei.com>
> ---
>  arch/arm64/kernel/ptrace.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 4532e9831856..3926ce6aa268 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -2346,15 +2346,18 @@ static __always_inline unsigned long 
> ptrace_save_reg(struct pt_regs *regs,
>       return saved_reg;
>  }
>  
> -static void report_syscall_entry(struct pt_regs *regs)
> +static int report_syscall_entry(struct pt_regs *regs)
>  {
>       unsigned long saved_reg;
> -     int regno;
> +     int regno, ret;
>  
>       saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
> -     if (ptrace_report_syscall_entry(regs))
> +     ret = ptrace_report_syscall_entry(regs);
> +     if (ret)
>               forget_syscall(regs);
>       regs->regs[regno] = saved_reg;
> +
> +     return ret;
>  }
>  
>  static void report_syscall_exit(struct pt_regs *regs)
> @@ -2381,10 +2384,11 @@ static void report_syscall_exit(struct pt_regs *regs)
>  int syscall_trace_enter(struct pt_regs *regs)
>  {
>       unsigned long flags = read_thread_flags();
> +     int ret;
>  
>       if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
> -             report_syscall_entry(regs);
> -             if (flags & _TIF_SYSCALL_EMU)
> +             ret = report_syscall_entry(regs);
> +             if (ret || (flags & _TIF_SYSCALL_EMU))

A small nit.

Could report_syscall_entry(regs) be checked directly in the 'if' conditional
code block thus dropping new 'ret' altogether ?

>                       return NO_SYSCALL;
>       }
>