linux-kernel - Re: [PATCH v7 02/11] arm64/ptrace: Refactor syscall_trace

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Message-ID: <d1aeb83e-d380-be80-9bd7-72f95a9aa09a@huawei.com>
Date: Thu, 20 Nov 2025 19:05:52 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Kevin Brodsky <kevin.brodsky@....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>, <akpm@...ux-foundation.org>,
	<ldv@...ace.io>, <macro@...am.me.uk>, <deller@....de>,
	<mark.rutland@....com>, <song@...nel.org>, <mbenes@...e.cz>,
	<ryan.roberts@....com>, <ada.coupriediaz@....com>,
	<anshuman.khandual@....com>, <broonie@...nel.org>, <pengcan@...inos.cn>,
	<dvyukov@...gle.com>, <kmal@...k.li>, <lihongbo22@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v7 02/11] arm64/ptrace: Refactor
 syscall_trace_enter/exit()



On 2025/11/19 1:09, Kevin Brodsky wrote:
> On 17/11/2025 14:30, Jinjie Ruan wrote:
>> [...]
>>
>> @@ -2386,19 +2384,27 @@ int syscall_trace_enter(struct pt_regs *regs)
>>  	if (secure_computing() == -1)
>>  		return NO_SYSCALL;
>>  
>> -	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
>> -		trace_sys_enter(regs, regs->syscallno);
>> +	/* Either of the above might have changed the syscall number */
>> +	syscall = syscall_get_nr(current, regs);
>> +
>> +	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) {
>> +		trace_sys_enter(regs, syscall);
>>  
>> -	audit_syscall_entry(regs->syscallno, regs->orig_x0, regs->regs[1],
>> +		/*
>> +		 * Probes or BPF hooks in the tracepoint may have changed the
>> +		 * system call number as well.
>> +		 */
>> +		 syscall = syscall_get_nr(current, regs);
>> +	}
>> +
>> +	audit_syscall_entry(syscall, regs->orig_x0, regs->regs[1],
>>  			    regs->regs[2], regs->regs[3]);
>>  
>>  	return regs->syscallno;
> 
> It would be good to align the return with the generic version as well.

Right, could be aligned with the return with the generic version.

> 
>>  }
>>  
>> -void syscall_trace_exit(struct pt_regs *regs)
>> +void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
>>  {
>> -	unsigned long flags = read_thread_flags();
>> -
>>  	audit_syscall_exit(regs);
>>  
>>  	if (flags & _TIF_SYSCALL_TRACEPOINT)
>> diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
>> index aba7ca6bca2d..6e3fe760e0bb 100644
>> --- a/arch/arm64/kernel/syscall.c
>> +++ b/arch/arm64/kernel/syscall.c
>> @@ -124,7 +124,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
>>  		 */
>>  		if (scno == NO_SYSCALL)
>>  			syscall_set_return_value(current, regs, -ENOSYS, 0);
>> -		scno = syscall_trace_enter(regs);
>> +		scno = syscall_trace_enter(regs, regs->syscallno, flags);
> 
> Nit: could use scno instead of regs->syscallno.

That is ok.

> 
> - Kevin
> 
>>  		if (scno == NO_SYSCALL)
>>  			goto trace_exit;
>>  	}
>> @@ -143,7 +143,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
>>  	}
>>  
>>  trace_exit:
>> -	syscall_trace_exit(regs);
>> +	flags = read_thread_flags();
>> +	syscall_trace_exit(regs, flags);
>>  }
>>  
>>  void do_el0_svc(struct pt_regs *regs)
>