OpenSBI: Boot HART ISA display

[Heinrich Schuchardt]

On 9/29/20 9:05 PM, Atish Patra wrote:
> On Mon, Sep 28, 2020 at 3:18 AM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>
>> Hello Atish,
>>
>> on the Kendryte 210 MaixDuino the OpenSBI output line
>>
>> Boot HART ISA       : rv64cicacsidcacsi
>>
>> looks a bit strange to me (see full output at the end of the mail).
>
> Yeah. It doesn't make any sense.
>
>> Assuming that the characters after rv64 are related to extensions I
>> would expect every letter appearing only once.
>>
>
> That's correct. See 3.1.1. Machine ISA Register misa in priv spec.
>
>> I tried to add sbi_printf() statements to lib/sbi/riscv_asm.c but they
>> do not print out correctly.
>>
>> After the following change:
>>
>> diff --git a/lib/sbi/riscv_asm.c b/lib/sbi/riscv_asm.c
>> index 8c54c11..a0c95a2 100644
>> --- a/lib/sbi/riscv_asm.c
>> +++ b/lib/sbi/riscv_asm.c
>> @@ -81,7 +81,7 @@ void misa_string(int xlen, char *out, unsigned int out_sz)
>>
>>         for (i = 0; i < array_size(valid_isa_order) && (pos < out_sz);
>> i++) {
>>                 if (misa_extension_imp(valid_isa_order[i]))
>> -                       out[pos++] = valid_isa_order[i];
>> +                       out[pos++] = '0' + i;
>>         }
>>
>>         if (pos < out_sz)
>>
>> the output becomes
>>
>> Boot HART ISA       : rv6403567;<@BCDHI
>>
>> I am clueless why valid_isa_order[i] is not evaluated correctly.
>>
>> When my changes are:
>>
>> diff --git a/lib/sbi/riscv_asm.c b/lib/sbi/riscv_asm.c
>> index 8c54c11..b1bbfc4 100644
>> --- a/lib/sbi/riscv_asm.c
>> +++ b/lib/sbi/riscv_asm.c
>> @@ -12,6 +12,8 @@
>>  #include <sbi/sbi_error.h>
>>  #include <sbi/sbi_platform.h>
>>
>> +static const char valid_isa_order[] = "iemafdqclbjtpvnsuhkorwxyzg";
>> +
>>  /* determine CPU extension, return non-zero support */
>>  int misa_extension_imp(char ext)
>>  {
>> @@ -52,7 +54,6 @@ int misa_xlen(void)
>>  void misa_string(int xlen, char *out, unsigned int out_sz)
>>  {
>>         unsigned int i, pos = 0;
>> -       const char valid_isa_order[] = "iemafdqclbjtpvnsuhkorwxyzg";
>>
>>         if (!out)
>>                 return;
>>
>> the output is:
>>
>> Boot HART ISA       : rv64imafdcsu
>>
>
> That's odd. Why does declaring valid_isa_order as static solve the issue ?
>
> Can you print the "misa" in misa_extension_imp () ?
> Just a guess: What if misa is not read correctly ?

No matter which values misa_extension_imp() returns we should only see
extension ID letters in the correct sequence.

"rv64cicacsidcacsi" is incorrect for any value of misa.

The interesting thing is that printf statements for strings that I
placed for debugging in misa_string() did not print correctly. Something
is going wrong here with strings.

It might be that some function is overwriting the area where the strings
are stored, e.g via the stack.

Best regards

Heinrich

>
>> I disassembled build/lib/sbi/riscv_asm.o but could not find a problem.
>>
>> Do you have a suggestion how to analyze this further?
>>
>> Best regards
>>
>> Heinrich
>>
>>
>>
>> OpenSBI v0.8-29-g7701ea1
>>    ____                    _____ ____ _____
>>   / __ \                  / ____|  _ \_   _|
>>  | |  | |_ __   ___ _ __ | (___ | |_) || |
>>  | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
>>  | |__| | |_) |  __/ | | |____) | |_) || |_
>>   \____/| .__/ \___|_| |_|_____/|____/_____|
>>         | |
>>         |_|
>>
>> Platform Name       : Kendryte K210
>> Platform Features   : timer
>> Platform HART Count : 2
>> Boot HART ID        : 0
>> Boot HART ISA       : rv64cicacsidcacsi
>> BOOT HART Features  : none
>> BOOT HART PMP Count : 0
>> BOOT HART MHPM Count: 0
>> Firmware Base       : 0x80000000
>> Firmware Size       : 100 KB
>> Runtime SBI Version : 0.2
>>
>> MIDELEG : 0x0000000000000222
>> MEDELEG : 0x0000000000000109
>>
>>
>> --
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>
>
>