PowerPC e7400 executable is type powerpc:e500 making debug difficult

[Joel Sherrill]

Hi

Chris and I discussed this for a few minutes last night and wondered if
code like this which includes arbitrary CPU model specific code could
be the culprit?

https://git.rtems.org/rtems/tree/bsps/powerpc/shared/exceptions/ppc_exc_initialize.c#n65

There may be other sections that do this.

If this were wrapped in a conditional for the proper CPU core variants, it
might resolve the issue. One would hope that if there were no e500 code,
binutils and gdb wouldn't get confused.

--joel

On Wed, Mar 27, 2024 at 12:19 PM Peter Dufault <dufault at hda.com> wrote:

> The PowerPC e7400 executables I built for the PowerPC-Beatnik BSP have an
> architecture of "powerpc:e500".  I assume it is like this for any powerpc
> target that includes "ppc_exc_initialize.c". This causes "GDB" to use the
> wrong size register set in remote debugging, and I couldn't figure out how
> to convince "gdb" to do something different.  I tried multiple settings but
> the "bfd_arch_info" wouldn't change from "powerpc:e500" (seen with "maint
> print architecture") and "gdb" continued to use the wrong register set size.
>
> (gdb) set powerpc vector-abi altivec
> (gdb) set arch powerpc:7400
> The target architecture is set to "powerpc:7400".
> (gdb) set gnutarget powerpc:7400
> (gdb) target remote 192.168.240.3:2159
> Remote debugging using 192.168.240.3:2159
> Remote 'g' packet reply is too long (expected 292 bytes, got 412 bytes):
> 003a5914007a0ae0007a7b6000000000006577e00052af140052af1c007a0ac80a010014003764ec000000000000000020000000006288500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000645760007a0ae0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000037265c0202b0324000000000376508003764ec00000000fff80000
> (gdb) maint print architecture
> gdbarch_dump: GDB_NM_FILE = <not-defined>
> gdbarch_dump: bfd_arch_info = powerpc:e500
> gdbarch_dump: byte_order = 0
> gdbarch_dump: byte_order_for_code = 0
> (...)
>
> This is because "ppc_exc_initialize.o" has a ".PPC.EMB.apuinfo" section
> that says it needs the "E500 SPE APU".  Here's what is in that section.
>
> 0 | 00000008 | 8 bytes in "APUinfo\0"
> 4 | 00000008 | 8 bytes (2 words) of APU information.
> 8 | 00000002 | Section type is rev 2.
> 12 | "APUinfo\0"
> 16 | 01000001 | APU 0x100 "e500 SPE APU" revision 1
> 20 | 00410001 | APU 0x041 "Motorola Book E Performance Monitor APU"
> revision 1.
>
> The resultant linked output is the superset of all requirements, so the
> linked output is also "powerpc:e500".
>
> This is because "ppc_exc_initialize.c" includes instructions for different
> targets that it avoids at run time.
>
> These code lines cause the ".o" to be "powerpc:e500":
>
> ppc_mtivor(32, ppc_exc_vector_address(ASM_E500_SPE_UNAVAILABLE_VECTOR,
> vector_base));
> ppc_mtivor(33, ppc_exc_vector_address(ASM_E500_EMB_FP_DATA_VECTOR,
> vector_base));
> ppc_mtivor(34, ppc_exc_vector_address(ASM_E500_EMB_FP_ROUND_VECTOR,
> vector_base));
>
> This line causes the ".o" to be "powerpc:titan" (if the above E500 lines
> are removed):
>
> ppc_mtivor(35, ppc_exc_vector_address(ASM_E500_PERFMON_VECTOR,
> vector_base));
>
> I "#ifdef'd" them out to get it to "work" but unless someone can figure
> out how to get rid of that section in the output "ppc_exc_initialize.c"
> needs to be changed to be conditionally compiled.
>
> If no one has any good ideas I'll open a bug with this.
>
> Peter
> -----------------
> Peter Dufault
> HD Associates, Inc.      Software and System Engineering
>
>
>
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