Bug 224872 - powerpc64: ddb breakpoints throwing a fast kernel trap
Summary: powerpc64: ddb breakpoints throwing a fast kernel trap
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: CURRENT
Hardware: powerpc Any
: --- Affects Only Me
Assignee: freebsd-ppc mailing list
Depends on:
Reported: 2018-01-03 17:53 UTC by Breno Leitao
Modified: 2019-01-07 22:21 UTC (History)
5 users (show)

See Also:


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Description Breno Leitao 2018-01-03 17:53:06 UTC
Trying to use DDB on powerpc64, I found that it throws a 0x400 exception.

OK boot -d
Kernel entry at 0x102620 ...
KDB: debugger backends: ddb
KDB: current backend: ddb
KDB: enter: Boot flags requested debugger
[ thread pid 0 tid 0 ]
Stopped at      .kdb_enter+0x60:        ld      r2, r1, 0x28

db> break platform_smp_start_cpu
db> continue

fatal kernel trap:

   exception       = 0x400 (instruction storage interrupt)
   virtual address = 0x426f6f7420666c60
   srr0            = 0x426f6f7420666c60 (0x426f6f7420666c60)
   srr1            = 0x8000000040001032
   lr              = 0x426f6f7420666c61 (0x426f6f7420666c61)
   curthread       = 0x114a100
          pid = 0, comm = 

[ thread pid 0 tid 0 ]
Stopped at      0x426f6f7420666c60
Comment 1 Justin Hibbits freebsd_committer 2018-01-03 18:06:18 UTC
0x426f6f7420666c60 Looks like a string: "Boot fl`"

I don't think anyone in powerpc-land has tried breakpoints in DDB recently.
Comment 2 Leonardo Bianconi 2018-12-21 15:15:48 UTC
This issue already has a solution: https://reviews.freebsd.org/D14484, but need to be tested in a 32bit machine.
If someone has access to a 32bit machine, please, could test it?
Comment 3 Mark Millard 2018-12-21 19:45:46 UTC
(In reply to Leonardo Bianconi from comment #2)

At least on old PowerMac G5's, 32-bit powerpc FreeBSD can boot
and run the 64-bit capable G5's. So some of the testing might
be able to be done that way?
Comment 4 Brandon Bergren 2019-01-07 22:21:12 UTC
I was able to verify this fix on my (32-bit) iBook G4. (Built without vt so the keyboard would work in early ddb)

Looks good here.