linux-kernel - Re: [PATCH v3] riscv: entry: set a0 = -ENOSYS only when syscall != -1

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Date:   Wed, 19 Jul 2023 18:28:47 +0200
From:   Björn Töpel <bjorn@...nel.org>
To:     Andreas Schwab <schwab@...e.de>,
        Celeste Liu <coelacanthushex@...il.com>
Cc:     Palmer Dabbelt <palmer@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
        Björn Töpel <bjorn@...osinc.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Felix Yan <felixonmars@...hlinux.org>,
        Ruizhe Pan <c141028@...il.com>,
        Shiqi Zhang <shiqi@...c.iscas.ac.cn>
Subject: Re: [PATCH v3] riscv: entry: set a0 = -ENOSYS only when syscall != -1

Andreas Schwab <schwab@...e.de> writes:

> On Jul 19 2023, Celeste Liu wrote:
>
>> @@ -308,7 +312,7 @@ asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs)
>>  
>>  		if (syscall < NR_syscalls)
>>  			syscall_handler(regs, syscall);
>> -		else
>> +		else if ((long)syscall != -1L)
>
> You can also use syscall != -1UL or even syscall != -1.

The former is indeed better for the eyes! :-) The latter will get a
-Wsign-compare warning, no?


Björn