[PATCH 3/3] lib: sbi_trap: Allow M-mode to M-mode ECALLs

[Daniel Schaefer]

On 9/9/20 1:04 PM, Anup Patel wrote:
> 
> 
>> -----Original Message-----
>> From: Atish Patra <atishp at atishpatra.org>
>> Sent: 08 September 2020 11:20
>> To: Anup Patel <Anup.Patel at wdc.com>
>> Cc: Atish Patra <Atish.Patra at wdc.com>; Alistair Francis
>> <Alistair.Francis at wdc.com>; Anup Patel <anup at brainfault.org>; OpenSBI
>> <opensbi at lists.infradead.org>
>> Subject: Re: [PATCH 3/3] lib: sbi_trap: Allow M-mode to M-mode ECALLs
>>
>> On Fri, Sep 4, 2020 at 5:14 AM Anup Patel <anup.patel at wdc.com> wrote:
>>>
>>> We should allow M-mode to M-mode ECALLs because:
>>> 1. No other mode can handle M-mode ECALLs 2. In future, we can allow
>>> M-mode baremetal application (not
>>>     linked to OpenSBI) running independently and cooperatively
>>>     without corrupting OpenSBI M-mode state (CSRs and memory).

Nice! I was wondering why this wasn't there and I thought maybe it's not allowed.
Good to see that there's nothing special about M-Mode making ecalls.

Since we now switch to S-Mode very early in EDK2, it doesn't make a difference for us.

>>> Signed-off-by: Anup Patel <anup.patel at wdc.com>
>>> ---
>>>   lib/sbi/sbi_trap.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c index
>>> b8bb20c..db5aa2f 100644
>>> --- a/lib/sbi/sbi_trap.c
>>> +++ b/lib/sbi/sbi_trap.c
>>> @@ -252,6 +252,7 @@ void sbi_trap_handler(struct sbi_trap_regs *regs)
>>>                  msg = "misaligned store handler failed";
>>>                  break;
>>>          case CAUSE_SUPERVISOR_ECALL:
>>> +       case CAUSE_MACHINE_ECALL:
>>>                  rc  = sbi_ecall_handler(regs);
>>>                  msg = "ecall handler failed";
>>>                  break;
>>> --
>>> 2.25.1
>>>
>>>
>>> --
>>> opensbi mailing list
>>> opensbi at lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/opensbi
>>
>>
>> Reviewed-by: Atish Patra <atish.patra at wdc.com>
> 
> Applied this patch to the riscv/opensbi repo
> 
> Regards,
> Anup
>