linux-kernel - Re: [PATCH 16/20] ARC: entry: Add more common chores to EXCEPTION

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Message-ID: <3f555ce3-1bf7-d55d-bf84-da75659f1042@kernel.org>
Date:   Sat, 19 Aug 2023 16:13:51 -0700
From:   Vineet Gupta <vgupta@...nel.org>
To:     Pavel.Kozlov@...opsys.com, Vineet Gupta <vgupta@...nel.org>,
        linux-snps-arc@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Shahab Vahedi <Shahab.Vahedi@...opsys.com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Subject: Re: [PATCH 16/20] ARC: entry: Add more common chores to
 EXCEPTION_PROLOGUE

On 8/18/23 05:56, Pavel.Kozlov@...opsys.com wrote:
> Hi Vineet,
>
>> Subject: [PATCH 16/20] ARC: entry: Add more common chores to
>>          EXCEPTION_PROLOGUE
>>
>> THe high level structure of most ARC exception handlers is
>>   1. save regfile with EXCEPTION_PROLOGUE
>>   2. setup r0: EFA (not part of pt_regs)
>>   3. setup r1: pointer to pt_regs (SP)
>>   4. drop down to pure kernel mode (from exception)
>>   5. call the Linux "C" handler
>>
>> Remove the boiler plate code by moving #2, #3, #4 into #1.
>>
>> The exceptions to most exceptions are syscall Trap and Machine check
>> which don't do some of above for various reasons, so call a newly
>> introduced variant EXCEPTION_PROLOGUE_KEEP_AE (same as original
>> EXCEPTION_PROLOGUE)
> I'm observing the ARC700 (nSIM) system freeze after this patch.
>
> ...
> f0000000.serial: ttyS0 at MMIO 0xf0000000 (irq = 24, base_baud = 3125000) is a 16550A
> printk: console [ttyS0] enabled
> printk: console [ttyS0] enabled
> printk: bootconsole [uart8250] disabled
> printk: bootconsole [uart8250] disabled
> NET: Registered PF_PACKET protocol family
> NET: Registered PF_KEY protocol family
> clk: Disabling unused clocks
> Freeing unused kernel image (initmem) memory: 2856K
> This architecture does not have kernel memory protection.
> Run /init as init process
>
>> @@ -128,11 +123,6 @@ ENTRY(EV_PrivilegeV)
>>
>>           EXCEPTION_PROLOGUE
>>
>> -       lr  r0, [efa]
>> -       mov r1, sp
>> -
>> -       FAKE_RET_FROM_EXCPN
>> -
>>           bl  do_privilege_fault
>>           b   ret_from_exception
> The same update is also required for the call_do_page_fault wrapper for ARcompact.

Indeed I missed that part.

-Vineet