Sunday, February 12, 2017

AIX KDB under 40p

Some news on 40p emulation: it's possible to launch the AIX kernel debugger under qemu-system-ppc.  For some reason the current PowerPC 601 CPU frequency is limited to 7.81 Mhz in the upstream qemu, so it takes more than a hour to load the debugger. But with a small modification it gets to the point within seconds.

The command line:

$ qemu-system-ppc -M 40p -bios p12h0456.img -hda aix-5.1-cd1.iso -cpu 601

^^^ -cpu 601 is crucial. With the default CPU (604) it just hangs after a greeting.

 And after 90 minutes,  on the serial line....

AIX Version pinmore.c, s.@(#)65 1.1
Instruction Storage Interrupt - PROC
[kdb_get_virtual_memory] no real storage @ 646E6D60
KDB(0)> f
pvthread+000000 STACK:
WARNING: bad IAR: 646E6D60, display stack from LR: 646E6D5D
KDB(0)> dr
r0  : 00000000  r1  : 00595910  r2  : 00595C58  r3  : 00000001  r4  : 01C08180
r5  : 00000000  r6  : 00000000  r7  : 00000000  r8  : 00000000  r9  : 00000000
r10 : 00000000  r11 : 00000000  r12 : 646E6D61  r13 : 00606178  r14 : 000000B8
r15 : 00000020  r16 : 00000020  r17 : 0803004D  r18 : 005AF0BC  r19 : 003FED04
r20 : 00606178  r21 : 00000020  r22 : 00606000  r23 : 00003F50  r24 : 00003F48
r25 : 00003F3C  r26 : 00000000  r27 : 63683A2C  r28 : 00003A24  r29 : 00003A20
r30 : 00590C70  r31 : 00000000

It's a pretty neat debugger somewhat similar to Solaris kadb:

KDB(0)> dc main 40
.main+000000     mflr    r0
.main+000004      lwz    r3,36E8(toc)        36E8(toc)=NON_DEBUG_AIX
.main+000008     stmw    r30,FFFFFFF8(stkp)
.main+00000C      stw    r0,8(stkp)
.main+000010       li    r0,1
.main+000014      stw    r0,0(r3)            r0=00000001
.main+000018     stwu    stkp,FFFFFFC0(stkp)
.main+00001C       bl    <.kdb_init>
.main+000020       bl    <.hardinit>
.main+000024       bl    <.vmsi>
.main+000028       bl    <.hardinit_defered>
.main+00002C       bl    <.init_locks>
.main+000030       bl    <.init_anyother_locks>
.main+000034       bl    <.ios_init>
.main+000038       bl    <.kdb_pin_symtable>
.main+00003C       bl    <.debugger_init>
.main+000040       bl    <.kx2init>
.main+000044       bl    <.kmem_init>
.main+000048       li    r3,B
.main+00004C       bl    <.i_enable>         r3=0000000B
.main+000050       bl    <.k_protect>
.main+000054       bl    <.wlm_ccb_init>
.main+000058       bl    <.strtdisp>
.main+00005C       bl    <.epost>
.main+000060       li    r4,0
.main+000064      lwz    r3,13C4(toc)        13C4(toc)=kernel_lock
.main+000068       bl    <.lockl>
.main+00006C       li    r30,0
.main+000070      lwz    r3,37EC(toc)        37EC(toc)=init_tbl

/stay tuned


Razvan Vilt said...

Have you tried loading veneer.exe from Windows NT?

atar said...

I haven't, but it probably won't work: NT switches the machine into a Big-endian mode, and I think it's only partially implemented.