Re: [patch 3/4] entry: Make return type of syscall_trace_enter() bool

[Radu Rendec]

On Sun, 2026-07-12 at 23:25 +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxx>
> 
> This prepares for changing the return types of
> syscall_enter_from_user_mode[_work]() to bool, which in turn separates the
> decision of invoking the syscall from the syscall number, which might have
> been changed in the call by ptrace, seccomp, tracing.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
> ---
>  include/linux/entry-common.h |   18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -72,7 +72,7 @@ static __always_inline long syscall_trac
>  	 */
>  	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
>  		if (syscall_user_dispatch(regs))
> -			return -1L;
> +			return false;
>  	}
>  
>  	/*
> @@ -87,13 +87,13 @@ static __always_inline long syscall_trac
>  	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
>  		if (!arch_ptrace_report_syscall_permit_entry(regs) ||
>  		    (work & SYSCALL_WORK_SYSCALL_EMU))
> -			return -1L;
> +			return false;
>  	}
>  
>  	/* Do seccomp after ptrace, to catch any tracer changes. */
>  	if (work & SYSCALL_WORK_SECCOMP) {
>  		if (!__seccomp_permit_syscall())
> -			return -1L;
> +			return false;
>  	}
>  
>  	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
> @@ -102,8 +102,7 @@ static __always_inline long syscall_trac
>  	if (unlikely(audit_context()))
>  		syscall_enter_audit(regs);
>  
> -	/* Either of the above might have changed the syscall number */
> -	return syscall_get_nr(current, regs);
> +	return true;
>  }
>  
>  /**
> @@ -133,8 +132,13 @@ static __always_inline long syscall_ente
>  {
>  	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
>  
> -	if (work & SYSCALL_WORK_ENTER)
> -		syscall = syscall_trace_enter(regs, work, syscall);
> +	if (work & SYSCALL_WORK_ENTER) {
> +		if (!syscall_trace_enter(regs, work, syscall))
> +			return -1L;
> +
> +		/* Reread the syscall number as it might have been modified */

nit: I would add "in the call above by ptrace, seccomp, tracing" - which
is actually in your commit message, but would make it immediately obvious
when reading the code.

> +		syscall = syscall_get_nr(current, regs);
> +	}
>  
>  	return syscall;
>  }

Reviewed-by: Radu Rendec <radu@xxxxxxxxxx>