[Crash-utility] [PATCH 01/16] Add MIPS64 framework code support

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> -----Original Message-----
> > Hi Kazu,
> >
> > On 03/12/2021 12:21 PM, HAGIO KAZUHITO(萩尾　一仁) wrote:
> >
> > > -----Original Message-----
> > >>>> --- a/diskdump.c
> > >>>> +++ b/diskdump.c
> > >>>> @@ -594,6 +594,9 @@ restart:
> > >>>>    	else if (STRNEQ(header->utsname.machine, "mips") &&
> > >>>>    	    machine_type_mismatch(file, "MIPS", NULL, 0))
> > >>>>    		goto err;
> > >>>> +	else if (STRNEQ(header->utsname.machine, "mips64") &&
> > >>>> +	    machine_type_mismatch(file, "MIPS", NULL, 0))
> > >>>> +		goto err;
> > >>> Why do you make MACHINE_TYPE the same as the MIPS one?
> > >>> With this, doesn't a MIPS64 crash match a MIPS vmcore?
> > >> The value of the machine type e_machine in mips32 or mips64 is MIPS, which
> > >> corresponds to EM_MIPS.
> > >> The definition in gdb-7.6/include/elf/common.h:110 is as follows:
> > >>       #define EM_MIPS        8        /* MIPS R3000 */
> > >> But there is no related definition of EM_MIPS64 or other mips64, so both
> > >> mips32 and mips64 should use EM_MIPS, and the corresponding e_machine is
> > >> MIPS.
> > >>
> > >> If the MACHINE_TYPE of mips64 is defined as MIPS64, as follows:
> > >>       define MACHINE_TYPE     "MIPS64"
> > >>
> > >> The following error will appear when running crash:
> > >>       WARNING: machine type mismatch:
> > >>                 crash utility: MIPS64
> > >>                 vmcore: MIPS
> > > Then, is there any problem with this?
> > >    machine_type_mismatch(file, "MIPS64", NULL, 0))
> > >
> > > This can prevent a mips64 crash from trying to open a mips32 vmcore
> > > and the reverse.
> > Read the ELF header information of vmocre (whether it is mips32 or mips64),
> > and the obtained machine type is MIPS, not MIPS64. In mips64, if you use
> > machine_type_mismatch(file, "MIPS64", NULL, 0)), there will be a machine
> > type
> > mismatch. You can only use machine_type_mismatch(file, "MIPS", NULL, 0)),
> > only then It can be successfully matched to the machine type.
> 
> Probably I misunderstand something, but then need to know it..
> 
> The machine_type_mismatch() doesn't use the ELF's EM_MIPS value.
> Why do we need to match crash's MACHINE_TYPE with ELF's EM_MIPS?
> 
> int
> machine_type(char *type)
> {
>         return STREQ(MACHINE_TYPE, type);
> }
> 
> int
> machine_type_mismatch(char *file, char *e_machine, char *alt, ulong query)
> {
>         if (machine_type(e_machine) || machine_type(alt))
>                 return FALSE;
> 
>         if (query == KDUMP_LOCAL)  /* already printed by NETDUMP_LOCAL */
>                 return TRUE;
> 
>         error(WARNING, "machine type mismatch:\n");
> 
>         fprintf(fp, "         crash utility: %s\n", MACHINE_TYPE);
>         fprintf(fp, "         %s: %s%s%s\n\n", file, e_machine,
>                 alt ? " or " : "", alt ? alt : "");
> 
>         return TRUE;
> }
> 
> Without the following hunk, EM_MIPS has been used only for ELF32 in symbols.c.
> 
> --- a/symbols.c
> +++ b/symbols.c
> @@ -3636,6 +3636,11 @@ is_kernel(char *file)
>                                 goto bailout;
>                         break;
> 
> +               case EM_MIPS:
> +                       if (machine_type_mismatch(file, "MIPS", NULL, 0))
> +                               goto bailout;
> +                       break;
> +
>                 default:
>                         if (machine_type_mismatch(file, "(unknown)", NULL, 0))
>                                 goto bailout;
> @@ -3890,6 +3895,11 @@ is_shared_object(char *file)
>                         if (machine_type("SPARC64"))
>                                 return TRUE;
>                         break;
> +
> +               case EM_MIPS:
> +                       if (machine_type("MIPS"))
> +                               return TRUE;
> +                       break;
>                 }
> 
> So I thought that meybe we can also change these ELF64 cases to "MIPS64"
> with defining MACHINE_TYPE as "MIPS64".
> 
> This is wrong?  e.g. mips32 also can use an ELF64 kernel/module binary?

If there is such a case, maybe we can also use these?:
  machine_type_mismatch(file, "MIPS", "MIPS64", 0)
  machine_type("MIPS") || machine_type("MIPS64")

I'm thinking that as we define the values/functions for mips64 separately
from mips32, it would be reasonable to make crash's MACHINE_TYPE different
from mips32 as well, and we can remove some unusual ifdefs.

Thanks,
Kazu

> > >
> > >> # readelf -h vmcore
> > >> ...
> > >>     Type:                              CORE (Core file)
> > >>     Machine:                           MIPS R3000
> > >> ...
> > >>
> > >> Therefore, the MACHINE_TYPE of mips32 and mips64 both define MIPS.
> > >>
> > >> Thanks,
> > >> Youling
> 
> 
> --
> Crash-utility mailing list
> Crash-utility at redhat.com
> https://listman.redhat.com/mailman/listinfo/crash-utility