[Crash-utility] Why module's global symbol cannot be displayed in crash? [ARM]

[Dave Anderson]

----- Original Message -----
> Mika,
> 
> On Fri, Mar 22, 2013 at 9:03 PM, Mika Westerberg
> <mika.westerberg at iki.fi> wrote:
> > On Thu, Mar 21, 2013 at 03:02:54PM -0400, Dave Anderson wrote:
> >> If for some reason you can't get them, I can make them available
> >> to you.
> >> And Lei Wen can also give you a sample dumpfile from his
> >> environment.
> >
> > Got them from Luc.
> >
> >> > Are you able to access module symbols on ARM dump (the one that
> >> > Luc provided)?
> >> > Or is it failing completely?
> >>
> >> I *think* so...
> >>
> >> This module text disassembly looks right:
> >>
> >> crash> dis usbnet_suspend
> >> 0xbf000ae8 <usbnet_suspend>:    push    {r3, r4, r5, lr}
> >> 0xbf000aec <usbnet_suspend+4>:  add     r0, r0, #32
> >> 0xbf000af0 <usbnet_suspend+8>:  mov     r5, r1
> >> 0xbf000af4 <usbnet_suspend+12>: bl      0xc01b8264
> >> <dev_get_drvdata>
> >> 0xbf000af8 <usbnet_suspend+16>: ldrb    r3, [r0, #36]   ; 0x24
> >> 0xbf000afc <usbnet_suspend+20>: mov     r4, r0
> >> 0xbf000b00 <usbnet_suspend+24>: add     r2, r3, #1
> >> 0xbf000b04 <usbnet_suspend+28>: cmp     r3, #0
> >> 0xbf000b08 <usbnet_suspend+32>: strb    r2, [r0, #36]   ; 0x24
> >> 0xbf000b0c <usbnet_suspend+36>: bne     0xbf000bdc
> >> <usbnet_suspend+244>
> >> 0xbf000b10 <usbnet_suspend+40>: mrs     r3, CPSR
> >> 0xbf000b14 <usbnet_suspend+44>: orr     r3, r3, #128    ; 0x80
> >> 0xbf000b18 <usbnet_suspend+48>: msr     CPSR_c, r3
> >> 0xbf000b1c <usbnet_suspend+52>: mov     r0, #1
> >> 0xbf000b20 <usbnet_suspend+56>: bl      0xc0015f40
> >> <add_preempt_count>
> >> 0xbf000b24 <usbnet_suspend+60>: ldr     r3, [r4, #200]  ; 0xc8
> >> 0xbf000b28 <usbnet_suspend+64>: cmp     r3, #0
> >> 0xbf000b2c <usbnet_suspend+68>: beq     0xbf000b70
> >> <usbnet_suspend+136>
> >> 0xbf000b30 <usbnet_suspend+72>: tst     r5, #1024       ; 0x400
> >> 0xbf000b34 <usbnet_suspend+76>: beq     0xbf000b70
> >> <usbnet_suspend+136>
> >> 0xbf000b38 <usbnet_suspend+80>: mrs     r3, CPSR
> >> ...
> >>
> >> This (r) data looks OK:
> >>
> >> crash> p smsc95xx_netdev_ops
> >> smsc95xx_netdev_ops = $8 = {
> >>   ndo_init = 0,
> >>   ndo_uninit = 0,
> >>   ndo_open = 0xbf000514 <usbnet_open>,
> >>   ndo_stop = 0xbf000bec <usbnet_stop>,
> >>   ndo_start_xmit = 0xbf001a60 <usbnet_start_xmit>,
> >>   ndo_select_queue = 0,
> >>   ndo_change_rx_flags = 0,
> >>   ndo_set_rx_mode = 0,
> >>   ndo_set_multicast_list = 0xbf008abc <smsc95xx_set_multicast>,
> >>   ndo_set_mac_address = 0xc025d854 <eth_mac_addr>,
> >>   ndo_validate_addr = 0xc025d6f8 <eth_validate_addr>,
> >>   ndo_do_ioctl = 0xbf00926c <smsc95xx_ioctl>,
> >>   ndo_set_config = 0,
> >>   ndo_change_mtu = 0xbf000de0 <usbnet_change_mtu>,
> >>   ndo_neigh_setup = 0,
> >>   ndo_tx_timeout = 0xbf000d4c <usbnet_tx_timeout>,
> >>   ndo_get_stats64 = 0,
> >>   ndo_get_stats = 0,
> >>   ndo_vlan_rx_add_vid = 0,
> >>   ndo_vlan_rx_kill_vid = 0,
> >>   ndo_set_vf_mac = 0,
> >>   ndo_set_vf_vlan = 0,
> >>   ndo_set_vf_tx_rate = 0,
> >>   ndo_get_vf_config = 0,
> >>   ndo_set_vf_port = 0,
> >>   ndo_get_vf_port = 0,
> >>   ndo_setup_tc = 0,
> >>   ndo_add_slave = 0,
> >>   ndo_del_slave = 0,
> >>   ndo_fix_features = 0,
> >> crash>
> >
> > I'm able to see the same.
> >
> > Setting suitable debug level reveals:
> >
> >         bf00f040 (bf00f000): scsi_wait_scan syms: 0 gplsyms: 0
> >         ksyms: 1
> >         bf00a1f8 (bf008000): smsc95xx syms: 0 gplsyms: 0 ksyms: 60
> >         bf002a40 (bf000000): usbnet syms: 0 gplsyms: 24 ksyms: 65
> >
> > The ksyms comes from KALLSYMS and by default it only includes text and
> > inittext symbols. This explains why Lei is not able to see data etc. symbols
> > when he runs 'sym -m <module>'.
> 
> Yep, that is my case. For data symbol would only be included in core section
> if CONFIG_KALLSYMS_ALL option is defined, so crash fail to extract
> the data symbol since it fail to see the data section is included in
> the dump image.
> 
> But what I am confused is that since mod -S would reload all module image,
> which already include all symbols. So why we should confine us to only
> extract those symbol in the core section defined by the dump image?

I explained that here: 

  https://www.redhat.com/archives/crash-utility/2013-March/msg00130.html

> I mean even with CONFIG_KALLSYMS be defined, I think it maybe doable to
> extract all data symbol. What are your guys' opinion here? :)

For whatever reason, there's seems to be something "different" about ARM 
module.ko files such that lm->mod_sections count seems to be incorrect?

It's been a long time since that SEC_FOUND business was added to the module
parsing code, and which I didn't write, and I don't recall how it should
work.  But that's where i would start looking.  

Dave