[uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[Antoine Martin]

Host is running 2.6.13.1

I tried mode=skas0 but it seems to always default to TT.
Or has this not been merged in mainline yet?


***
Here is a strace of a x86 guest:
strace ./kernel32 mode=skas0 root=/dev/ubda mem=384M ubd0=./root_fs32
console0=fd:0,fd:1
(..)


gettimeofday({2451808977522855, 18446659740416081920}, NULL) = 0
open("/tmp/vm_file-WEUjnm", O_RDWR|O_CREAT|O_EXCL, 0600) = 5
unlink("/tmp/vm_file-WEUjnm")           = 0
fchmod(5, 0777)                         = 0
_llseek(5, 402653184, [402653184], SEEK_SET) = 0
write(5, "\0", 1)                       = 1
fcntl64(5, F_SETFD, FD_CLOEXEC)         = 0
mmap2(0xa0800000, 394264576, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED,
5, 0x800) = 0xffffffffa0800000
mkdir("/root/.uml/", 0777)              = -1 EEXIST (File exists)
mkdir("/root/.uml/1", 0777)             = 0
open("/root/.uml/1/pid", O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0644) = 6
getpid()                                = 6026
write(6, "6026\n", 5)                   = 5
close(6)                                = 0
mprotect(0xa0256000, 8192, PROT_READ|PROT_WRITE|PROT_EXEC) = 0
rt_sigaction(SIGPIPE, {0x1000000000000001, [], 0}, {SIG_DFL}, 8) = 0
socketcall(0x8, 0xffffc360)             = 0
fcntl64(6, F_SETFD, FD_CLOEXEC)         = 0
fcntl64(7, F_SETFD, FD_CLOEXEC)         = 0
rt_sigaction(SIGWINCH, {0x10000000a0019a60, [], 0}, {SIG_DFL}, 8) = 0
getpid()                                = 6026
write(1, "tracing thread pid = 6026\n", 26tracing thread pid = 6026
) = 26
clone(child_stack=0xa0257fd4, flags=CLONE_FILES|SIGCHLD) = 6027
--- SIGCHLD (Child exited) @ 0 (0) ---
waitpid(6027, [{WIFSTOPPED(s) && WSTOPSIG(s) == SIGSTOP}], WSTOPPED) =
6027
ptrace(0x15 /* PTRACE_??? */, 6027, 0, 0x1) = 0
ptrace(PTRACE_CONT, 6027, 0, SIG_0)     = 0
rt_sigaction(SIGSEGV, {0x10000000a0019be0, [], 0}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGUSR1, {0x10000000a00184f0, [], 0}, {SIG_DFL}, 8) = 0
waitpid(4294967295, [{WIFSTOPPED(s) && WSTOPSIG(s) == SIGSEGV}],
WSTOPPED) = 6027
--- SIGCHLD (Child exited) @ 0 (0) ---
ptrace(PTRACE_CONT, 6027, 0, SIGSEGV)   = 0
waitpid(4294967295, [{WIFSTOPPED(s) && WSTOPSIG(s) == SIGUSR1}],
WSTOPPED) = 6027
--- SIGCHLD (Child exited) @ 0 (0) ---
munmap(0, 2692743168)                   = 0
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++



**
And here is a amd64 guest:
(This trace was much much longer)
(...)
It seems to spin for an awful long time on:
rt_sigprocmask(SIG_BLOCK, [], NULL, 8)  = 0
rt_sigprocmask(SIG_SETMASK, NULL, [], 8) = 0
rt_sigprocmask(SIG_BLOCK, [ALRM VTALRM IO], NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [ALRM VTALRM IO], [ALRM VTALRM IO], 8) = 0

Reducing the ram seemed to help, no idea what this is about!

Another weirdness, this command line works:
# ./kernel64 root=/dev/ubda mem=256M ubd0=./root_fs64
eth0=tuntap,tap0,FE:F0:00:00:00:01,10.0.0.254 eth1=pcap,eth0
console0=fd:0,fd:1 umid=1
But this one does not:
# ./kernel64 root=/dev/ubda mem=256M ubd0=./root_fs64
eth0=tuntap,tap0,FE:F0:00:00:00:01,10.0.0.254 eth1=pcap,eth0
console0=fd:0,fd:1 console=pty umid=1 gentoo=nodevfs nodevfs selinux=1
enforcing=0
With this one it crashes after checking for PROT_EXEC.
Is this to do with command line size limitations?


** Last issue, when running in a 2.6.14-rc1 guest, I can't 'emerge
--sync', it dies before rebuilding its cache:
Here is the strace:
(..)
>>> checking server timestamp ...

>>>
>>> Timestamps on the server and in the local repository are the same.
>>> Cancelling all further sync action. You are already up to date.
>>>

) = 247
ioctl(2, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7f7fc2da50) = -1 ENOTTY
(Inappropriate ioctl for device)
stat("/var/log/emerge.log", {st_mode=S_IFREG|0660, st_size=222087, ...})
= 0
open("/var/log/emerge.log", O_WRONLY|O_APPEND|O_CREAT, 0666) = 3
fstat(3, {st_mode=S_IFREG|0660, st_size=222087, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= 0x40018000
fstat(3, {st_mode=S_IFREG|0660, st_size=222087, ...}) = 0
lseek(3, 222087, SEEK_SET)              = 222087
fstat(3, {st_mode=S_IFREG|0660, st_size=222087, ...}) = 0
fcntl(3, F_SETLK, {type=F_WRLCK, whence=SEEK_SET, start=0, len=0}) = 0
fstat(3, {st_mode=S_IFREG|0660, st_size=222087, ...}) = 0
lseek(3, 222087, SEEK_SET)              = 222087
write(3, "1126803520:  *** terminating.\n", 30) = 30
fcntl(3, F_SETLKW, {type=F_UNLCK, whence=SEEK_SET, start=0, len=0}) = 0
close(3)                                = 0
munmap(0x40018000, 4096)                = 0
ioctl(2, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7f7fc2daf0) = -1 ENOTTY
(Inappropriate ioctl for device)
wait4(-1, 0x7f7fc2e034, 0, NULL)        = -1 ECHILD (No child processes)
open("/var/cache/edb/mtimedb", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
fstat(3, {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
fstat(3, {st_mode=S_IFREG|0664, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= 0x40018000
write(3, "\200\2}q\1(U\4infoq\2}q\3(U\17/usr/share/i"..., 1772) = 1772
close(3)                                = 0
munmap(0x40018000, 4096)                = 0
chown("/var/cache/edb/mtimedb", 0, 250) = 0
chmod("/var/cache/edb/mtimedb", 0664)   = 0
rt_sigaction(SIGINT, NULL, {0x403330d0, [], SA_RESTORER, 0x40b72ba0}, 8)
= 0
rt_sigaction(SIGINT, {SIG_DFL}, NULL, 8) = 0
rt_sigaction(SIGTERM, NULL, {0x403330d0, [], SA_RESTORER, 0x40b72ba0},
8) = 0
rt_sigaction(SIGTERM, {SIG_DFL}, NULL, 8) = 0
munmap(0x4009f000, 200704)              = 0
close(4)                                = 0
munmap(0x40016000, 4096)                = 0
munmap(0x40017000, 4096)                = 0
exit_group(0)                           = ?


Any clues?

Thanks
Antoine



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Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[Jeff Dike]

On Thu, Sep 15, 2005 at 06:05:51PM +0100, Antoine Martin wrote:
> I tried mode=skas0 but it seems to always default to TT.
> Or has this not been merged in mainline yet?

It's in mainline.  What's the guest?

> **
> And here is a amd64 guest:
> (This trace was much much longer)

Did this one come up in skas0 or tt mode?

> Another weirdness, this command line works:
> # ./kernel64 root=/dev/ubda mem=256M ubd0=./root_fs64
> eth0=tuntap,tap0,FE:F0:00:00:00:01,10.0.0.254 eth1=pcap,eth0
> console0=fd:0,fd:1 umid=1

What's with the console* business?  The switch is "con".

> But this one does not:
> # ./kernel64 root=/dev/ubda mem=256M ubd0=./root_fs64
> eth0=tuntap,tap0,FE:F0:00:00:00:01,10.0.0.254 eth1=pcap,eth0
> console0=fd:0,fd:1 console=pty umid=1 gentoo=nodevfs nodevfs selinux=1
> enforcing=0
> With this one it crashes after checking for PROT_EXEC.
> Is this to do with command line size limitations?

Maybe, but it probably shouldn't crash.

> write(3, "1126803520:  *** terminating.\n", 30) = 30

This bit seems relevent - were there any syscall failures above that?

				Jeff


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Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[antoine]

On Thu, 2005-09-15 at 15:06 -0400, Jeff Dike wrote:
> On Thu, Sep 15, 2005 at 06:05:51PM +0100, Antoine Martin wrote:
> > I tried mode=skas0 but it seems to always default to TT.
> > Or has this not been merged in mainline yet?
> 
> It's in mainline.  What's the guest?
2.6.14-rc1

> > **
> > And here is a amd64 guest:
> > (This trace was much much longer)
> 
> Did this one come up in skas0 or tt mode?
I think it was tt (will check tomorrow on that box)
As I said above, it seems to always use TT, ignoring mode=skas0

> > Another weirdness, this command line works:
> > # ./kernel64 root=/dev/ubda mem=256M ubd0=./root_fs64
> > eth0=tuntap,tap0,FE:F0:00:00:00:01,10.0.0.254 eth1=pcap,eth0
> > console0=fd:0,fd:1 umid=1
> 
> What's with the console* business?  The switch is "con".
DOH Can't trust my memory! That's why I try to use scripts..

> > But this one does not:
> > # ./kernel64 root=/dev/ubda mem=256M ubd0=./root_fs64
> > eth0=tuntap,tap0,FE:F0:00:00:00:01,10.0.0.254 eth1=pcap,eth0
> > console0=fd:0,fd:1 console=pty umid=1 gentoo=nodevfs nodevfs selinux=1
> > enforcing=0
> > With this one it crashes after checking for PROT_EXEC.
> > Is this to do with command line size limitations?
> 
> Maybe, but it probably shouldn't crash.
Yep, it isn't even that big.
> 
> > write(3, "1126803520:  *** terminating.\n", 30) = 30
> 
> This bit seems relevent - were there any syscall failures above that?
What I am looking for?
I could just drop the full log on a public server if that helps.

Antoine



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Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[Jeff Dike]

On Thu, Sep 15, 2005 at 11:35:01PM +0100, antoine wrote:
> after issuing a uml_mconsole N reboot, I got (from stdout):
> " * Starting local...  [ ok ]
> deactivate_all_fds failed, errno = 9
> 
> I/O possible"

Was this booting up or shutting down?  The "starting local" business
suggests booting, but deactivate_all_fds is only called at shutdown.

I'm chasing a similar bug, which seems to be exercised by hotplugging
devices.

				Jeff


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Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[antoine]

Here is another problem that may be of interest:
host is 2.6.13.1 amd64
guest is 2.6.14-rc1

after issuing a uml_mconsole N reboot, I got (from stdout):
" * Starting local...  [ ok ]
deactivate_all_fds failed, errno = 9

I/O possible"

And the guest just stopped there. Not sure why.

Antoine



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Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[antoine]

On Thu, 2005-09-15 at 18:28 -0400, Jeff Dike wrote:
> On Thu, Sep 15, 2005 at 11:35:01PM +0100, antoine wrote:
> > after issuing a uml_mconsole N reboot, I got (from stdout):
> > " * Starting local...  [ ok ]
> > deactivate_all_fds failed, errno = 9
> > 
> > I/O possible"
> 
> Was this booting up or shutting down?  The "starting local" business
> suggests booting, but deactivate_all_fds is only called at shutdown.
'starting local' was the last message of the boot process (no login
screen on this console)
I was shutting down with uml_mconsole N reboot
(I believe this does the equivalent of a 'init 6')
This instance was quite short on memory - which may have caused or
helped trigger this.

Antoine

> I'm chasing a similar bug, which seems to be exercised by hotplugging
> devices.
> 
> 				Jeff



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Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[Rob Landley]

[-- Attachment #1: Type: text/plain, Size: 1697 bytes --]

On Thursday 15 September 2005 16:39, antoine wrote:
> On Thu, 2005-09-15 at 15:06 -0400, Jeff Dike wrote:
> > On Thu, Sep 15, 2005 at 06:05:51PM +0100, Antoine Martin wrote:
> > > I tried mode=skas0 but it seems to always default to TT.
> > > Or has this not been merged in mainline yet?
> >
> > It's in mainline.  What's the guest?
>
> 2.6.14-rc1
>
> > > **
> > > And here is a amd64 guest:
> > > (This trace was much much longer)
> >
> > Did this one come up in skas0 or tt mode?
>
> I think it was tt (will check tomorrow on that box)
> As I said above, it seems to always use TT, ignoring mode=skas0

I have a little trick I do, which is to build a minimal UML with hostfs 
(sample config file attached), and then booting it ala:

./linux rootfstype=hostfs rootflags=/ rw mem=48M init=/bin/sh

This should come up with /bin/sh as pid 1 attached to /dev/console which is 
going to stdin and stdout of the UML process.  (I.E. bog simple uml wrapper 
for a command shell.)

If I compile it in tt mode, it works fine on ubuntu (hoar-infested hedgehog 
release).

If I compile it instead for skas mode, it makes it all the way to mounting the 
rootfs (which it will only do if skas0 is in, because the ubuntu host kernel 
doesn't have skas support), but then barfs saying it can't intialize the TLS 
environment, kills PID 1, dumps a panic, and gives me my host kernel's shell 
prompt back.

(Easy way to tell which system you're running: "whoami".  If it says root, 
you're in the child kernel.  "mount -t proc /proc /proc" followed by 
"cat /proc/cpuinfo" is good too...)

When I build both in, skas0 wins (at least in that it gives me the can't setup 
tls message and corresponding panic).

Rob

[-- Attachment #2: config-uml --]
[-- Type: text/plain, Size: 1451 bytes --]

CONFIG_GENERIC_HARDIRQS=y
CONFIG_UML=y
CONFIG_MMU=y
CONFIG_UID16=y
CONFIG_RWSEM_GENERIC_SPINLOCK=y
CONFIG_GENERIC_CALIBRATE_DELAY=y
CONFIG_IRQ_RELEASE_METHOD=y
CONFIG_MODE_SKAS=y
CONFIG_UML_X86=y
CONFIG_TOP_ADDR=0xc0000000
CONFIG_STUB_CODE=0xbfffe000
CONFIG_STUB_DATA=0xbffff000
CONFIG_STUB_START=0xbfffe000
CONFIG_ARCH_HAS_SC_SIGNALS=y
CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA=y
CONFIG_FLATMEM=y
CONFIG_FLAT_NODE_MEM_MAP=y
CONFIG_LD_SCRIPT_DYN=y
CONFIG_NET=y
CONFIG_BINFMT_ELF=y
CONFIG_HOSTFS=y
CONFIG_NEST_LEVEL=0
CONFIG_KERNEL_HALF_GIGS=1
CONFIG_KERNEL_STACK_ORDER=2
CONFIG_CLEAN_COMPILE=y
CONFIG_BROKEN_ON_SMP=y
CONFIG_INIT_ENV_ARG_LIMIT=32
CONFIG_LOCALVERSION=""
CONFIG_SYSCTL=y
CONFIG_KOBJECT_UEVENT=y
CONFIG_KALLSYMS=y
CONFIG_PRINTK=y
CONFIG_BUG=y
CONFIG_BASE_FULL=y
CONFIG_FUTEX=y
CONFIG_EPOLL=y
CONFIG_SHMEM=y
CONFIG_CC_ALIGN_FUNCTIONS=0
CONFIG_CC_ALIGN_LABELS=0
CONFIG_CC_ALIGN_LOOPS=0
CONFIG_CC_ALIGN_JUMPS=0
CONFIG_BASE_SMALL=0
CONFIG_PACKET=y
CONFIG_UNIX=y
CONFIG_STANDALONE=y
CONFIG_STDERR_CONSOLE=y
CONFIG_STDIO_CONSOLE=y
CONFIG_XTERM_CHAN=y
CONFIG_NOCONFIG_CHAN=y
CONFIG_CON_ZERO_CHAN="fd:0,fd:1"
CONFIG_CON_CHAN="xterm"
CONFIG_SSL_CHAN="pty"
CONFIG_UNIX98_PTYS=y
CONFIG_BLK_DEV_LOOP=y
CONFIG_BLK_DEV_RAM_COUNT=16
CONFIG_INITRAMFS_SOURCE=""
CONFIG_LBD=y
CONFIG_IOSCHED_NOOP=y
CONFIG_NETDEVICES=y
CONFIG_EXT3_FS=y
CONFIG_JBD=y
CONFIG_DNOTIFY=y
CONFIG_PROC_FS=y
CONFIG_SYSFS=y
CONFIG_RAMFS=y
CONFIG_MSDOS_PARTITION=y
CONFIG_LOG_BUF_SHIFT=14

Re: [uml-devel] 2.6.14-rc1 x86 on 2.6.13.1 amd64 host: guest segfaults

[Blaisorblade]

On Thursday 15 September 2005 19:05, Antoine Martin wrote:
> Host is running 2.6.13.1

> I tried mode=skas0 but it seems to always default to TT.
The correct switch is skas0, mode=skas0 doesn't exist (maybe to fix). Just 
verified looking at vmlinux --help output.
> Or has this not been merged in mainline yet?
The only idea I can have about this is that you didn't compile skas mode in at 
all. Which makes sense since you never ran a x86_64 SKAS guest until skas0 
was born.

In fact,if you have both TT and SKAS0 in, it by default chooses always skas0, 
unless you say mode=tt.

If you can verify (on *that* kernel, with --showconfig) it's not your fault, 
I'll check the sources.
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade


		
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