OpenSBI: Boot HART ISA display

[Atish Patra]

On Tue, Sep 29, 2020 at 12:38 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> 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.
>

You are correct.

> "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.
>

+ Damien

I just remembered Damien was facing a similar issue on Kendryte while
running the test payload where
it would not work if a string is used but worked fine if a single
character is printed in a loop.

@Damien : Did you figure out the cause for that issue you were seeing?

> 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
> >>
> >>
> >> --
> >> opensbi mailing list
> >> opensbi at lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/opensbi
> >
> >
> >
>


-- 
Regards,
Atish