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Date:      Mon, 5 Oct 2020 12:12:25 -0600
From:      Warner Losh <imp@bsdimp.com>
To:        Xin LI <d@delphij.net>
Cc:        FreeBSD Current <freebsd-current@freebsd.org>, Warner Losh <imp@freebsd.org>
Subject:   Re: GPF on boot with devmatch
Message-ID:  <CANCZdfpx3GTjuZNCdxne9YuWPukU8hn6R_TBwv-CaLfQ=GqP8A@mail.gmail.com>
In-Reply-To: <95d6ce61-06af-eb12-9a6e-2b8342663dc7@delphij.net>
References:  <1dec1b9d-03e7-7171-9f48-71573dafead4@delphij.net> <CANCZdfqNtsFY83uk8s7dbe3ikDaGuR1G_HpG-en27R4M65P3uw@mail.gmail.com> <95d6ce61-06af-eb12-9a6e-2b8342663dc7@delphij.net>

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On Sun, Oct 4, 2020 at 11:30 PM Xin Li <delphij@delphij.net> wrote:

>
>
> On 10/4/20 10:13 PM, Warner Losh wrote:
> >
> >
> > On Sun, Oct 4, 2020, 11:07 PM Xin Li <delphij@delphij.net
> > <mailto:delphij@delphij.net>> wrote:
> >
> >     Hi,
> >
> >     I'm seeing this panic at boot after upgrading from r366217 to
> r366364,
> >     and continues to exist for r366421 (but I haven't find out the exact
> >     change that caused it).  Preloading the relevant kernel modules
> >     (uhid.ko, ums.ko and wmt.ko) seems to make the kernel boot correctly.
> >
> >
> > What happens if you disable devmatch and load these modules by hand?
>
> Loading these modules from loader or kld_list will prevent this panic
> regardless if devmatch is enabled.
>
> > What happens if you load them from rc.d scripts with devmatch disabled?
>
> It seems that the devmatch was started by devd and not rc.  Disabling
> devmatch (setting devmatch_enable="NO" without loading any of these klds
> would not provoke the panic).
>

That sounds like a bug to me... I'll have to look into it. I'm mostly
asking 'what happens if you load them after boot' to see if this is a
'devmatch doing weird things' issue or a 'these drivers don't like to be
loaded so late and we need to track down why' issue.

Warner


> > Warner
> >
> >     This is not reproducible on my laptop, which will load many more
> kernel
> >     modules.
> >
> >     ===
> >     Autoloading module: uhid.ko
> >     Autoloading module: wmt.ko
> >
> >
> >     Fatal trap 9: general protection fault while in kernel mode
> >     cpuid = 2; apic id = 04
> >     instruction pointer     = 0x20:0xffffffff806ad6eb
> >     stack pointer           = 0x28:0xfffffe01850cd960
> >     frame pointer           = 0x28:0xfffffe01850cd9e0
> >     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         = 740 (devmatch)
> >     trap number             = 9
> >     panic: general protection fault
> >     cpuid = 3
> >     time = 1601866799
> >     KDB: stack backtrace:
> >     db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> >     0xfffffe01850cd670
> >     vpanic() at vpanic+0x182/frame 0xfffffe01850cd6c0
> >     panic() at panic+0x43/frame 0xfffffe01850cd720
> >     trap_fatal() at trap_fatal+0x387/frame 0xfffffe01850cd780
> >     trap() at trap+0xa4/frame 0xfffffe01850cd890
> >     calltrap() at calltrap+0x8/frame 0xfffffe01850cd890
> >     --- trap 0x9, rip = 0xffffffff806ad6eb, rsp = 0xfffffe01850cd960,
> rbp =
> >     0xfffffe01850cd9e0 ---
> >     sysctl_devices() at sysctl_devices+0x24b/frame 0xfffffe01850cd9e0
> >     sysctl_root_handler_locked() at sysctl_root_handler_locked+0x9c/frame
> >     0xfffffe01850cda30
> >     sysctl_root() at sysctl_root+0x20a/frame 0xfffffe01850cdab0
> >     userland_sysctl() at userland_sysctl+0x17d/frame 0xfffffe01850cdb60
> >     sys___sysctl() at sys___sysctl+0x5f/frame 0xfffffe01850cdc10
> >     amd64_syscall() at amd64_syscall+0x135/frame 0xfffffe01850cdd30
> >     fast_syscall_common() at fast_syscall_common+0xf8/frame
> >     0xfffffe01850cdd30
> >     --- syscall (202, FreeBSD ELF64, sys___sysctl), rip = 0x80038968a,
> rsp =
> >     0x7fffffffd988, rbp = 0x7fffffffd9c0 ---
> >     ===
> >
> >     sysctl_devices+0x24b (0x6dab) was:
> >
> >             sb->s_len += strlen(p);
> >         6d50:       4c 89 e7                mov    %r12,%rdi
> >         6d53:       e8 00 00 00 00          callq  6d58
> >     <sysctl_devices+0x1f8>
> >         6d58:       48 01 45 b0             add    %rax,-0x50(%rbp)
> >         6d5c:       48 8d 7d 88             lea    -0x78(%rbp),%rdi
> >             sbuf_putc(&sb, '\0');
> >         6d60:       31 f6                   xor    %esi,%esi
> >         6d62:       e8 00 00 00 00          callq  6d67
> >     <sysctl_devices+0x207>
> >             MPASS((sb->s_flags & SBUF_INCLUDENUL) == 0);
> >         6d67:       f6 45 b8 02             testb  $0x2,-0x48(%rbp)
> >         6d6b:       0f 85 10 01 00 00       jne    6e81
> >     <sysctl_devices+0x321>
> >             if (sb->s_error != 0)
> >         6d71:       83 7d a0 00             cmpl   $0x0,-0x60(%rbp)
> >         6d75:       0f 85 8c 00 00 00       jne    6e07
> >     <sysctl_devices+0x2a7>
> >             p = EOB(sb);
> >         6d7b:       4c 8b 65 88             mov    -0x78(%rbp),%r12
> >         6d7f:       48 8b 45 b0             mov    -0x50(%rbp),%rax
> >             *p = '\0';      /* sbuf buffer isn't NUL terminated until
> >     sbuf_finish() */
> >         6d83:       41 c6 04 04 00          movb   $0x0,(%r12,%rax,1)
> >             space = SPACE(sb);
> >         6d88:       4c 8b 6d a8             mov    -0x58(%rbp),%r13
> >         6d8c:       4c 2b 6d b0             sub    -0x50(%rbp),%r13
> >             if (space <= 1) {
> >         6d90:       49 83 fd 01             cmp    $0x1,%r13
> >         6d94:       77 09                   ja     6d9f
> >     <sysctl_devices+0x23f>
> >                     sb->s_error = ENOMEM;
> >         6d96:       c7 45 a0 0c 00 00 00    movl   $0xc,-0x60(%rbp)
> >         6d9d:       eb 68                   jmp    6e07
> >     <sysctl_devices+0x2a7>
> >         6d9f:       49 01 c4                add    %rax,%r12
> >             return (dev->parent);
> >         6da2:       48 8b 7b 28             mov    0x28(%rbx),%rdi
> >             if (parent == NULL) {
> >         6da6:       48 85 ff                test   %rdi,%rdi
> >         6da9:       74 4b                   je     6df6
> >     <sysctl_devices+0x296>
> >             KOBJOPLOOKUP(((kobj_t)_dev)->ops,bus_child_location_str);
> >         6dab:       48 8b 07                mov    (%rdi),%rax
> >         6dae:       48 c7 c2 00 00 00 00    mov    $0x0,%rdx
> >         6db5:       0f b6 0d 00 00 00 00    movzbl 0x0(%rip),%ecx
> #
> >     6dbc <sysctl_devices+0x25c>
> >         6dbc:       4c 8b 04 c8             mov    (%rax,%rcx,8),%r8
> >         6dc0:       49 39 10                cmp    %rdx,(%r8)
> >         6dc3:       74 22                   je     6de7
> >     <sysctl_devices+0x287>
> >         6dc5:       48 8d 34 c8             lea    (%rax,%rcx,8),%rsi
> >         6dc9:       48 89 7d d0             mov    %rdi,-0x30(%rbp)
> >         6dcd:       48 8b b8 00 08 00 00    mov    0x800(%rax),%rdi
> >         6dd4:       48 c7 c2 00 00 00 00    mov    $0x0,%rdx
> >         6ddb:       e8 00 00 00 00          callq  6de0
> >     <sysctl_devices+0x280>
> >         6de0:       48 8b 7d d0             mov    -0x30(%rbp),%rdi
> >         6de4:       49 89 c0                mov    %rax,%r8
> >             rc = ((bus_child_location_str_t *) _m)(_dev, _child, _buf,
> >     _buflen);
> >         6de7:       48 89 de                mov    %rbx,%rsi
> >
>



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