linux-kernel - Re: [PATCH v9 02/16] arm64/ptrace: Split report

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Message-ID: <b66f285f-20d8-4c29-ad0d-1ab0857b38b0@arm.com>
Date: Mon, 8 Dec 2025 10:32:12 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>, catalin.marinas@....com,
 will@...nel.org, oleg@...hat.com, tglx@...utronix.de, peterz@...radead.org,
 luto@...nel.org, shuah@...nel.org, kees@...nel.org, wad@...omium.org,
 deller@....de, macro@...am.me.uk, charlie@...osinc.com,
 kevin.brodsky@....com, ldv@...ace.io, mark.rutland@....com, song@...nel.org,
 ryan.roberts@....com, ada.coupriediaz@....com, broonie@...nel.org,
 pengcan@...inos.cn, dvyukov@...gle.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v9 02/16] arm64/ptrace: Split report_syscall()

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.brodsky@....com>
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>

LGTM.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....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);
>  }