Date: Mon, 27 Feb 2012 15:35:54 +0100 From: Bengt Ahlgren <bengta@sics.se> To: Konstantin Belousov <kostikbel@gmail.com> Cc: emulation@freebsd.org Subject: Re: [Bengt Ahlgren] 8.3-PRERELEASE panic in linux emulation Message-ID: <uh7obskbayd.fsf@P142.sics.se> In-Reply-To: <20120227143143.GE55074@deviant.kiev.zoral.com.ua> (Konstantin Belousov's message of "Mon, 27 Feb 2012 16:31:43 %2B0200") References: <uh762ewxvpv.fsf@P142.sics.se> <20120224142940.GR55074@deviant.kiev.zoral.com.ua> <uh739a0w39k.fsf@P142.sics.se> <uh7fwe054u4.fsf@P142.sics.se> <20120225011228.GB55074@deviant.kiev.zoral.com.ua> <uh762es5tlz.fsf@P142.sics.se> <20120227143143.GE55074@deviant.kiev.zoral.com.ua>
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Konstantin Belousov <kostikbel@gmail.com> writes:
> On Mon, Feb 27, 2012 at 01:49:28PM +0100, Bengt Ahlgren wrote:
>> Konstantin Belousov <kostikbel@gmail.com> writes:
>>
>> > On Fri, Feb 24, 2012 at 09:55:31PM +0100, Bengt Ahlgren wrote:
>> >> Bengt Ahlgren <bengta@sics.se> writes:
>> >>
>> >> > Konstantin Belousov <kostikbel@gmail.com> writes:
>> >> >
>> >> >> On Fri, Feb 24, 2012 at 01:27:24PM +0100, Bengt Ahlgren wrote:
>> >> >>> Hello!
>> >> >>>
>> >> >>> Perhaps emulation@ is a better place to report this problem?
>> >> >>>
>> >> >>> Bengt
>> >> >>>
>> >> >>
>> >> >>> From: Bengt Ahlgren <bengta@sics.se>
>> >> >>> To: stable@freebsd.org
>> >> >>> Subject: 8.3-PRERELEASE panic in linux emulation
>> >> >>> Date: Thu, 23 Feb 2012 17:26:32 +0100
>> >> >>>
>> >> >>> Hi!
>> >> >>>
>> >> >>> I get a consistent panic when starting acroread after updating to
>> >> >>> 8.3-PRERELEASE. An 8.2-STABLE from Feb 4th was OK. Can provide more
>> >> >>> info if needed.
>> >> >>>
>> >> >>> Bengt
>> >> >>>
>> >> >>> FreeBSD xx.yy.zz 8.3-PRERELEASE FreeBSD 8.3-PRERELEASE #13 r231999: Wed Feb 22 21:01:38 CET 2012 bengta@P142.sics.se:/usr/obj/usr/src/sys/P142-82 i386
>> >> >>>
>> >> >>> Fatal trap 12: page fault while in kernel mode
>> >> >>> fault virtual address = 0xbfbfdffc
>> >> >>> fault code = supervisor write, page not present
>> >> >>> instruction pointer = 0x20:0xc50b396c
>> >> >>> stack pointer = 0x28:0xe7481a6c
>> >> >>> frame pointer = 0x28:0xe7481a90
>> >> >>> code segment = base 0x0, limit 0xfffff, type 0x1b
>> >> >>> = DPL 0, pres 1, def32 1, gran 1
>> >> >>> processor eflags = interrupt enabled, resume, IOPL = 0
>> >> >>> current process = 1997 (bash)
>> >> >>> trap number = 12
>> >> >>> panic: page fault
>> >> >>> KDB: stack backtrace:
>> >> >>> db_trace_self_wrapper(c091af2a,70797420,78302065,a0d6231,c5d6b600,...) at db_trace_self_wrapper+0x26
>> >> >>> kdb_backtrace(c0919061,c09b49a0,c0900251,e7481910,e7481910,...) at kdb_backtrace+0x2a
>> >> >>> panic(c0900251,c0941cab,c5c246e8,1,1,...) at panic+0xaf
>> >> >>> trap_fatal(c0670d02,0,e7481964,80400,c5c24580,...) at trap_fatal+0x353
>> >> >>> trap_pfault(e74819cc,bfbfe190,c5c24580,202,c5cecac0,...) at trap_pfault+0x87
>> >> >>> trap(e7481a2c) at trap+0x453
>> >> >>> calltrap() at calltrap+0x6
>> >> >>> --- trap 0xc, eip = 0xc50b396c, esp = 0xe7481a6c, ebp = 0xe7481a90 ---
>> >> >>> elf_linux_fixup(e7481c0c,e7481b98,c065ca92,c60ffce8,100000,...) at elf_linux_fixup+0x33c
>> >> >>> kern_execve(c5c24580,e7481c3c,0,8112710,8116cd8,...) at kern_execve+0x7d6
>> >> >>> linux_execve(c5c24580,e7481cec,c,c,c,...) at linux_execve+0xa7
>> >> >>> syscall(e7481d28) at syscall+0x372
>> >> >>> Xint0x80_syscall() at Xint0x80_syscall+0x21
>> >> >>> --- syscall (11, Linux ELF, linux_execve), eip = 0x281e0d4a, esp = 0xbfbfd644, ebp = 0xbfbfd7e8 ---
>> >> >>>
>> >> >>> #0 doadump () at pcpu.h:244
>> >> >>> #1 0xc05de609 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:441
>> >> >>> #2 0xc05de84f in panic (fmt=Variable "fmt" is not available.
>> >> >>> ) at /usr/src/sys/kern/kern_shutdown.c:614
>> >> >>> #3 0xc08b22c3 in trap_fatal (frame=0xe7481a2c, eva=3217022972) at /usr/src/sys/i386/i386/trap.c:981
>> >> >>> #4 0xc08b2357 in trap_pfault (frame=0xe7481a2c, usermode=0, eva=3217022972) at /usr/src/sys/i386/i386/trap.c:843
>> >> >>> #5 0xc08b3133 in trap (frame=0xe7481a2c) at /usr/src/sys/i386/i386/trap.c:562
>> >> >>> #6 0xc089bedc in calltrap () at /usr/src/sys/i386/i386/exception.s:168
>> >> >>> #7 0xc50b396c in elf_linux_fixup (stack_base=0xe7481c0c, imgp=0xe7481b98) at /usr/src/sys/modules/linux/../../i386/linux/linux_sysvec.c:288
>> >> >>> #8 0xc05ac636 in kern_execve (td=0xc5c24580, args=0xe7481c3c, mac_p=0x0) at /usr/src/sys/kern/kern_exec.c:551
>> >> >>> #9 0xc50ab387 in linux_execve (td=0xc5c24580, args=0xe7481cec) at /usr/src/sys/modules/linux/../../i386/linux/linux_machdep.c:143
>> >> >>> #10 0xc08b2902 in syscall (frame=0xe7481d28) at subr_syscall.c:114
>> >> >>> #11 0xc089bf41 in Xint0x80_syscall () at /usr/src/sys/i386/i386/exception.s:266
>> >> >>> #12 0x00000033 in ?? ()
>> >> >>>
>> >> >> I am not sure if this is the real cause of your panic, but the line from
>> >> >> the backtrace indeed has a bug. Please try the change below.
>> >> >>
>> >> >> diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c
>> >> >> index 7634138..d4e23e1 100644
>> >> >> --- a/sys/i386/linux/linux_sysvec.c
>> >> >> +++ b/sys/i386/linux/linux_sysvec.c
>> >> >> @@ -227,11 +227,11 @@ linux_fixup(register_t **stack_base, struct image_params *imgp)
>> >> >> argv = *stack_base;
>> >> >> envp = *stack_base + (imgp->args->argc + 1);
>> >> >> (*stack_base)--;
>> >> >> - **stack_base = (intptr_t)(void *)envp;
>> >> >> + suword(*stack_base, (intptr_t)(void *)envp);
>> >> >> (*stack_base)--;
>> >> >> - **stack_base = (intptr_t)(void *)argv;
>> >> >> + suword(*stack_base, (intptr_t)(void *)argv);
>> >> >> (*stack_base)--;
>> >> >> - **stack_base = imgp->args->argc;
>> >> >> + suword(*stack_base, imgp->args->argc);
>> >> >> return (0);
>> >> >> }
>> >> >>
>> >> >> @@ -286,7 +286,7 @@ elf_linux_fixup(register_t **stack_base, struct image_params *imgp)
>> >> >> imgp->auxargs = NULL;
>> >> >>
>> >> >> (*stack_base)--;
>> >> >> - **stack_base = (register_t)imgp->args->argc;
>> >> >> + suword(*stack_base, (register_t)imgp->args->argc);
>> >> >> return (0);
>> >> >> }
>> >> >>
>> >> >
>> >> > Thanks for the response! I will try the patch, but that file has not
>> >> > been touched since June 2011. I was suspecting the changes in r231146
>> >> > and r231148. If there is no change with your patch I will roll back
>> >> > those to see what happens.
>> > This is very unlikely. fadvise() has nothing to do with image activators.
>> >
>> >>
>> >> No panics so far. That patch does indeed seem to solve the problem! I
>> >> also verified with going back to the old kernel, which again
>> >> consistently paniced.
>> > I will commit the change in minutes. Kernel must not access usermode
>> > addresses directly.
>> >
>> > But, does the application that used to panic the system, behave properly ?
>>
>> Yes, it (acroread8) does behave properly with the patch. Have not
>> tested extensively, however.
>>
>> >> Thanks very much for good work!
>> >>
>> >> I'm a but puzzled though, because that bug must have been there for
>> >> quite some time without triggering the panic.
>> > The panic with unpatched kernel looks puzzling. Do you have some
>> > non-default stack limit ? Can you look at the resource limit values
>> > for the process initiated the panic ?
>>
>> Not that I'm aware of. Unless the acroread launch script does this. I
>> don't know how to check this for a running process, but "limits|grep
>> stack" in a regular shell gives me:
>>
>> stacksize 65536 kB
>>
>> Or, do you mean that I can dig that out of the crash dump? If so, I'll
>> need some help with how to.
>
> From the kgdb, frame 8, print the content of td->td_proc->p_limit.
Is this it?
(kgdb) frame 8
#8 0xc05ac636 in kern_execve (td=0xc5dc3000, args=0xe7535c3c, mac_p=0x0)
at /usr/src/sys/kern/kern_exec.c:551
551 (*p->p_sysent->sv_fixup)(&stack_base, imgp);
(kgdb) print td->td_proc->p_limit
$1 = (struct plimit *) 0xc5490700
(kgdb) print *td->td_proc->p_limit
$2 = {pl_rlimit = {{rlim_cur = 9223372036854775807,
rlim_max = 9223372036854775807}, {rlim_cur = 9223372036854775807,
rlim_max = 9223372036854775807}, {rlim_cur = 536870912,
rlim_max = 536870912}, {rlim_cur = 67108864, rlim_max = 67108864}, {
rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}, {
rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}, {
rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}, {
rlim_cur = 5547, rlim_max = 5547}, {rlim_cur = 11095, rlim_max = 11095},
{rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}, {
rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}, {
rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}, {
rlim_cur = 9223372036854775807, rlim_max = 9223372036854775807}},
pl_refcnt = 51}
Bengt
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