linux-kernel - Re: [PATCH V7 13/20] riscv: compat: process: Add UXL_32 support in start

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Message-ID: <509d2b62-7d52-bf5c-7a6c-213a740a5c00@codethink.co.uk>
Date:   Fri, 11 Mar 2022 13:37:48 +0000
From:   Ben Dooks <ben.dooks@...ethink.co.uk>
To:     Guo Ren <guoren@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
        Arnd Bergmann <arnd@...db.de>,
        Anup Patel <anup@...infault.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        liush <liush@...winnertech.com>, Wei Fu <wefu@...hat.com>,
        Drew Fustini <drew@...gleboard.org>,
        Wang Junqiang <wangjunqiang@...as.ac.cn>,
        Christoph Hellwig <hch@....de>
Cc:     linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-csky@...r.kernel.org,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V7 13/20] riscv: compat: process: Add UXL_32 support in
 start_thread

On 11/03/2022 02:38, Guo Ren wrote:
> Hi Arnd,
> 
> On Mon, Feb 28, 2022 at 12:30 AM <guoren@...nel.org> wrote:
>>
>> From: Guo Ren <guoren@...ux.alibaba.com>
>>
>> If the current task is in COMPAT mode, set SR_UXL_32 in status for
>> returning userspace. We need CONFIG _COMPAT to prevent compiling
>> errors with rv32 defconfig.
>>
>> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
>> Signed-off-by: Guo Ren <guoren@...nel.org>
>> Cc: Arnd Bergmann <arnd@...db.de>
>> Cc: Palmer Dabbelt <palmer@...belt.com>
>> ---
>>   arch/riscv/kernel/process.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
>> index 03ac3aa611f5..54787ca9806a 100644
>> --- a/arch/riscv/kernel/process.c
>> +++ b/arch/riscv/kernel/process.c
>> @@ -97,6 +97,11 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
>>          }
>>          regs->epc = pc;
>>          regs->sp = sp;
>> +
> FIxup:
> 
> + #ifdef CONFIG_COMPAT
>> +       if (is_compat_task())
>> +               regs->status = (regs->status & ~SR_UXL) | SR_UXL_32;
>> +       else
>> +               regs->status = (regs->status & ~SR_UXL) | SR_UXL_64;
> + #endif
> 
> We still need "#ifdef CONFIG_COMPAT" here, because for rv32 we can't
> set SR_UXL at all. SR_UXL is BIT[32, 33].

would an if (IS_ENABLED(CONFIG_COMPAT)) { } around the lot be better
than an #ifdef here?

>>   }
>>
>>   void flush_thread(void)
>> --
>> 2.25.1
>>
> 
> 


-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

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