Re: [uml-user] Re: UML immediate segfault on RHEL4 regardless CONFIG_HOST_2G_2G
Blaisorblade <blaisorblade <at> yahoo.it>
2005-12-13 18:14:51 GMT
On Tuesday 13 December 2005 08:18, Karamazov Brothers wrote:
> Hi all,
>
> A bit more debugging information. Gdb shows that ./linux segfaults
> at the same location in os_early_checks () at
> arch/um/os-Linux/start_up.c:264
> no matter CONFIG_HOST_2G_2G is defined or not. Any clue how to fix?
I know this hang well, but until now I saw it just when I enable either SMP or
spinlock debugging enabled.
FOR Jeff Dike:
It seems due (for what I saw) to a process faulting in a page from the stack
area (it's still the initial stack, so mapped VM_GROWSDOWN) with an address <
%esp.
And as you know, the kernel says that you are buggy, and it's indeed right
since a concurrent signal handler would kill you.
This started showing up with the Ingo Molnar's locking restructure and
abstraction, for me. He reimplemented spinlock debugging, and then spinlock
debugging started triggering this. I'm not sure this is the correct
diagnosis, but when I debugged it (or similar crashes), this sounded
reasonable.
However, in this case, the hang is going on on logbuf_lock, so it puzzles me a
lot.
> See my earlier email below for my kernel settings. Thanks for your help.
> Ken
> # gdb ./linux
> Program received signal SIGSEGV, Segmentation fault.
lock value below is invalid, GDB is messing on the stack with
> _raw_spin_lock (lock=0x602bfb70) at include/asm/thread_info.h:47
> 47 {
> (gdb) bt
> #0 _raw_spin_lock (lock=0x602bfb70) at include/asm/thread_info.h:47
> #1 0x000000006020de18 in _spin_lock_irqsave (lock=0x602bfb70)
> at kernel/spinlock.c:78
> #2 0x000000006002d777 in vprintk (
> fmt=0x60234ee8 "Checking that ptrace can change system call
> numbers...", args=0x7fbffff470) at kernel/printk.c:540
> #3 0x000000006002d730 in printk (fmt=Variable "fmt" is not available.
> ) at kernel/printk.c:516
> #4 0x0000000060026989 in os_early_checks () at
> arch/um/os-Linux/start_up.c:264
> #5 0x0000000060019e7f in linux_main (argc=1, argv=0x7fbffff908)
> at arch/um/kernel/um_arch.c:336
> #6 0x0000000060012fda in main (argc=1, argv=0x7fbffff908,
> envp=0x7fbffff918)
> at arch/um/kernel/main.c:152
> On 12/13/05, Karamazov Brothers <karamazov.brothers <at> gmail.com> wrote:
> > Hi all,
> >
> > Puzzled and need some help.
> >
> > I downloaded the stock linux-2.6.14.3.tar.bz2, and
> > tried to make ARCH=um on RedHat's Enterprise Linux 4 update 2. And the
> > output segfaults immediately.
> >
> > My procedures are as follows:
> > 1) cd linux-2.6.14.3
Here, you possibly could benefit from a "make defconfig ARCH=um" to get a
basis .config - {menu,x,*}config tend to pick host settings (which are not
good for UML) as default.
> > 2) make menuconfig ARCH=um
> > 2a) enable CONFIG_HOST_2G_2G, or
> > 2b) disable CONFIG_HOST_2G_2G
> > and accept all other defaults.
> > 3) make linux ARCH=um
> > 4) ./linux --> immediate segfault (for both config 2a and 2b)
> >
> > My RHEL4 update 2 is running kernel-2.6.9-22.EL.
> >
> > I tried many many other prebuilt binaries from various
> > sites. Most of them fail. What should I do to make it work?
Wait a moment - most of them fail is strange, but
a) if some works that's a good point - we may later need to distinguish
between working and not working ones.
b) failures could be due to different reasons. The above one is almost surely
due to SMP/spinlock debug, but released binaries shouldn't have these options
enabled.
--
--
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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