Debug linux binary with enable linux emulation

Tue May 12 17:30:08 UTC 2020

Dne 2020-05-12 00:49, freebsd at sysctl.cz napsal:
> Dne 2020-05-11 13:56, Konstantin Belousov napsal:
>> On Mon, May 11, 2020 at 12:28:23AM +0200, freebsd at sysctl.cz wrote:
>>> Hi,
>>> I tried debug with gdb for linux emulation
>>> and have issue with kernel panic.
>>> 
>>> kldload linux64.ko
>>> gdb ./Discord or other linux binary
>>> 
>>> Fatal trap 12: page fault while in kernel mode
>>> cpuid = 3; apic id = 03
>>> fault virtual address	= 0x18
>>> fault code		= supervisor read data, page not present
>>> instruction pointer	= 0x20:0xffffffff82f5b682
>>> stack pointer	        = 0x28:0xfffffe00691fd980
>>> frame pointer	        = 0x28:0xfffffe00691fd9e0
>>> code segment		= base 0x0, limit 0xfffff, type 0x1b
>>> 			= DPL 0, pres 1, long 1, def32 0, gran 1
>>> processor eflags	= interrupt enabled, resume, IOPL = 0
>>> current process		= 17392 (fish)
>>> trap number		= 12
>>> panic: page fault
>>> cpuid = 3
>>> time = 1589132677
>>> KDB: stack backtrace:
>>> #0 0xffffffff80c1d2f7 at kdb_backtrace+0x67
>>> #1 0xffffffff80bd062d at vpanic+0x19d
>>> #2 0xffffffff80bd0483 at panic+0x43
>>> #3 0xffffffff810a7dcc at trap_fatal+0x39c
>>> #4 0xffffffff810a7e19 at trap_pfault+0x49
>>> #5 0xffffffff810a740f at trap+0x29f
>>> #6 0xffffffff81081bdc at calltrap+0x8
>>> #7 0xffffffff82f503d1 at linux_thread_detach+0x21
>> Show the line number for linux_thread_detach+0x21.
>> Or better, compile with INVARIANTS, it should fire an assertion.
>> Then get a core dump.
>> 
>>> #8 0xffffffff80be5acf at thread_suspend_check+0x41f
>>> #9 0xffffffff80c32ed9 at ast+0x3b9
>>> #10 0xffffffff810850e9 at doreti_ast+0x1f
>>> Uptime: 2h56m24s
>>> Dumping 1146 out of 8042
>>> MB:..2%..12%..21%..31%..41%..51%..62%..72%..81%..91%---<<BOOT>>---
>>> Copyright (c) 1992-2019 The FreeBSD Project.
>>> 
>>> GNU gdb (GDB) 9.1 [GDB v9.1 for FreeBSD]
>>> Copyright (C) 2020 Free Software Foundation, Inc.
>>> License GPLv3+: GNU GPL version 3 or later
>>> <http://gnu.org/licenses/gpl.html>
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>>> Type "show copying" and "show warranty" for details.
>>> This GDB was configured as "x86_64-portbld-freebsd12.1".
>>> Type "show configuration" for configuration details.
>>> For bug reporting instructions, please see:
>>> <http://www.gnu.org/software/gdb/bugs/>.
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>>>     <http://www.gnu.org/software/gdb/documentation/>.
>>> 
>>> For help, type "help".
>>> Type "apropos word" to search for commands related to "word"...
>>> Reading symbols from /boot/kernel/kernel...
>>> (No debugging symbols found in /boot/kernel/kernel)
>>> 0xffffffff80c01eda in sched_switch ()
>>> (kgdb)
>>> (kgdb)
>>> (kgdb) bt
>>> #0  0xffffffff80c01eda in sched_switch ()
>>> #1  0xffffffff80bdbfa2 in mi_switch ()
>>> #2  0xffffffff80c2bb75 in sleepq_catch_signals ()
>>> #3  0xffffffff80c2be64 in sleepq_timedwait_sig ()
>>> #4  0xffffffff80bdb9a5 in _sleep ()
>>> #5  0xffffffff80bf1ee3 in umtxq_sleep ()
>>> #6  0xffffffff80bf1c90 in do_wait ()
>>> #7  0xffffffff80bef8fe in __umtx_op_wait_uint_private ()
>>> #8  0xffffffff810a8984 in amd64_syscall ()
>>> #9  <signal handler called>
>>> #10 0x000000080974dedc in ?? ()
>>> Backtrace stopped: Cannot access memory at address 0x7fffffffddc8
>>> 
>>> I have now kernel without debug symbols.
>>> 
>>> M.
>>> _______________________________________________
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>>> "freebsd-emulation-unsubscribe at freebsd.org"
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> 
> 
> 
> Hi konstantin,
> I have good news, now we can look detail
> 
> (kgdb) bt
> #0  __curthread () at /usr/src/sys/amd64/include/pcpu.h:234
> #1  doadump (textdump=<optimized out>) at 
> /usr/src/sys/kern/kern_shutdown.c:371
> #2  0xffffffff80bd0228 in kern_reboot (howto=260) at
> /usr/src/sys/kern/kern_shutdown.c:451
> #3  0xffffffff80bd0689 in vpanic (fmt=<optimized out>, ap=<optimized
> out>) at /usr/src/sys/kern/kern_shutdown.c:877
> #4  0xffffffff80bd0483 in panic (fmt=<unavailable>) at
> /usr/src/sys/kern/kern_shutdown.c:804
> #5  0xffffffff810a7dcc in trap_fatal (frame=0xfffffe00634e58c0,
> eva=24) at /usr/src/sys/amd64/amd64/trap.c:943
> #6  0xffffffff810a7e19 in trap_pfault (frame=0xfffffe00634e58c0,
> usermode=0) at /usr/src/sys/amd64/amd64/trap.c:767
> #7  0xffffffff810a740f in trap (frame=0xfffffe00634e58c0) at
> /usr/src/sys/amd64/amd64/trap.c:443
> #8  <signal handler called>
> #9  release_futexes (td=<optimized out>, em=0x0) at
> /usr/src/sys/compat/linux/linux_futex.c:1283
> #10 0xffffffff82f503d1 in linux_thread_detach (td=0xfffff8014bd935e0)
> at /usr/src/sys/compat/linux/linux_fork.c:466
> #11 0xffffffff80be5acf in thread_suspend_check (return_instead=0) at
> /usr/src/sys/kern/kern_thread.c:1010
> #12 0xffffffff80c32ed9 in ast (framep=0xfffffe00634e5ac0) at
> /usr/src/sys/kern/subr_trap.c:342
> #13 0xffffffff810850e9 in doreti_ast () at
> /usr/src/sys/amd64/amd64/exception.S:1149
> #14 0x0000000800bb7008 in ?? ()
> #15 0x000000000000000f in ?? ()
> #16 0x0000000000000000 in ?? ()
> (kgdb) list 0xffffffff82f503d1
> Function "0xffffffff82f503d1" not defined.
> (kgdb) list *0xffffffff82f503d1
> 0xffffffff82f503d1 is in linux_thread_detach
> (/usr/src/sys/compat/linux/linux_fork.c:468).
> warning: Source file is more recent than executable.
> 463
> 464        LINUX_CTR1(thread_detach, "thread(%d)", em->em_tid);
> 465
> 466        release_futexes(td, em);
> 467
> 468        child_clear_tid = em->child_clear_tid;
> 469
> 470        if (child_clear_tid != NULL) {
> 471
> 472            LINUX_CTR2(thread_detach, "thread(%d) %p",
> (kgdb)
> 
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Hi Konstantin,
do you have any idea with debug this kernel panic ?
M.