Rob Landley wrote:
So I took the rollup patch I posted earlier (which made things work on
x86-64), and tried to compile it on my x86 Ubuntu "Horny Hedgehog" laptop. I
had to revert the /lib64 change, of course. (I need to come up with a good
fix for that.)
I also needed to change one more thing: replacing <asm/signal.h> with
<signal.h> in skas-i386/stub_segv.c. (I.E. the same kind of fix I had to
make for skas-x86_64/stub_segv.c.)
That got it to build. Here's the panic and the dissassembly:
Initialized stdio console driver
Console initialized on /dev/tty0
Failed to open 'root_fs', errno = 2
VFS: Mounted root (hostfs filesystem).
Stub registers -
0 - 0
1 - 0
2 - 0
3 - 0
4 - 0
5 - 0
6 - 0
7 - 7b
8 - 7b
9 - 0
10 - 33
11 - ffffffff
12 - 40000c20
13 - 73
14 - 210246
15 - bf55ec10
16 - 7b
Kernel panic - not syncing: get_skas_faultinfo : failed to wait for
SIGUSR1/SIGTRAP, pid = 13213, n = 13213, errno = 0, status = 0xb7f
EIP: 0073:[<40000c20>] CPU: 0 Not tainted ESP: 007b:bf55ec10 EFLAGS: 00210246
Not tainted
EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000
ESI: 00000000 EDI: 00000000 EBP: 00000000 DS: 007b ES: 007b
088a7bac: [<08080b5d>] notifier_call_chain+0x2d/0x50
088a7bc8: [<080714a1>] panic+0x71/0x110
088a7be0: [<0805e910>] wait_stub_done+0x100/0x190
088a7c60: [<0805ea1a>] get_skas_faultinfo+0x7a/0xa0
088a7c70: [<0806a081>] save_registers+0x41/0x80
088a7c78: [<08060602>] user_signal+0x62/0x70
088a7c8c: [<0805f0f0>] userspace+0x180/0x220
088a7cd8: [<08055f50>] init+0x0/0x170
088a7ce4: [<0805fc12>] new_thread_handler+0xf2/0x130
Oh, this implies, that registers already have been restored successfully
after processing of stub_segv!
So I guess, SIGUSR1 isn't unblocked at sigreturn or there is no SIGUSR1
in the queue for userspace (don't ask me why ...). In that case userspace
wouldn't stop at stub_segv's sigreturn, but would try to run the segfaulted
code, which again segfaults, as first segfault is unhandled yet.
If so, just handling SIGSEGV the same way as SIGUSR1 or SIGSTOP in
wait_stub_done() could work around the problem. (Not a solution, but a test
only)
081130b0 <stub_segv_handler>:
81130b0: 8b 44 24 5c mov 0x5c(%esp),%eax
81130b4: 8d 54 24 08 lea 0x8(%esp),%edx
81130b8: a3 04 f0 ff bf mov %eax,0xbffff004
81130bd: 8b 44 24 3c mov 0x3c(%esp),%eax
81130c1: a3 00 f0 ff bf mov %eax,0xbffff000
81130c6: 8b 44 24 38 mov 0x38(%esp),%eax
81130ca: a3 08 f0 ff bf mov %eax,0xbffff008
81130cf: 89 d0 mov %edx,%eax
81130d1: 89 c4 mov %eax,%esp
81130d3: b8 77 00 00 00 mov $0x77,%eax
81130d8: cd 80 int $0x80
81130da: c3 ret
This looks fine.
Bodo
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