Paul Menzel <pmenzel@xxxxxxxxxxxxx> writes:
> Dear Linux folks,
Hi Paul,
> On the POWER8 server IBM S822LC running Ubuntu 21.10, building Linux
> 5.17-rc2+ with rcutorture tests
I'm not sure if that's the host kernel version or the version you're
using of rcutorture? Can you tell us the sha1 of your host kernel and of
the tree you're running rcutorture from?
> $ tools/testing/selftests/rcutorture/bin/torture.sh --duration 10
>
> the built init
>
> $ file tools/testing/selftests/rcutorture/initrd/init
> tools/testing/selftests/rcutorture/initrd/init: ELF 64-bit LSB
> executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), statically
> linked, BuildID[sha1]=0ded0e45649184a296f30d611f7a03cc51ecb616, for
> GNU/Linux 3.10.0, stripped
Mine looks pretty much identical:
$ file tools/testing/selftests/rcutorture/initrd/init
tools/testing/selftests/rcutorture/initrd/init: ELF 64-bit LSB
executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), statically
linked, BuildID[sha1]=86078bf6e5d54ab0860d36aa9a65d52818b972c8, for
GNU/Linux 3.10.0, stripped
> segfaults in QEMU. From one of the log files
But mine doesn't segfault, it runs fine and the test completes.
What qemu version are you using?
I tried 4.2.1 and 6.2.0, both worked.
> /dev/shm/linux/tools/testing/selftests/rcutorture/res/2022.02.01-21.52.37-torture/results-rcutorture/TREE03/console.log
>
> [ 1.119803][ T1] Run /init as init process
> [ 1.122011][ T1] init[1]: segfault (11) at f0656d90 nip 10000a18 lr 0 code 1 in init[10000000+d0000]
> [ 1.124863][ T1] init[1]: code: 2c2903e7 f9210030 4081ff84 4bffff58 00000000 01000000 00000580 3c40100f
> [ 1.128823][ T1] init[1]: code: 38427c00 7c290b78 782106e4 38000000 <f821ff81> 7c0803a6 f8010000 e9028010
The disassembly from 3c40100f is:
lis r2,4111
addi r2,r2,31744
mr r9,r1
rldicr r1,r1,0,59
li r0,0
stdu r1,-128(r1) <- fault
mtlr r0
std r0,0(r1)
ld r8,-32752(r2)
I think you'll find that's the code at the ELF entry point. You can
check with:
$ readelf -e tools/testing/selftests/rcutorture/initrd/init | grep Entry
Entry point address: 0x10000c0c
$ objdump -d tools/testing/selftests/rcutorture/initrd/init | grep -m 1 -A 8 10000c0c
10000c0c: 0e 10 40 3c lis r2,4110
10000c10: 00 7b 42 38 addi r2,r2,31488
10000c14: 78 0b 29 7c mr r9,r1
10000c18: e4 06 21 78 rldicr r1,r1,0,59
10000c1c: 00 00 00 38 li r0,0
10000c20: 81 ff 21 f8 stdu r1,-128(r1)
10000c24: a6 03 08 7c mtlr r0
10000c28: 00 00 01 f8 std r0,0(r1)
10000c2c: 10 80 02 e9 ld r8,-32752(r2)
The fault you're seeing is the first store using the stack pointer (r1),
which is setup by the kernel.
The fault address f0656d90 is weirdly low, the stack should be up near 128TB.
I'm not sure how we end up with a bad r1.
Can you dump some info about the kernel that was built, something like:
$ file /dev/shm/linux/tools/testing/selftests/rcutorture/res/2022.02.01-21.52.37-torture/results-rcutorture/TREE03/vmlinux
And maybe paste/attach the full log, maybe there's a clue somewhere.
cheers
