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<p class=MsoNormal>Hi,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I was investigating a 64 bit linux kernel dump . I have following
doubts regarding usage of crash.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>1) I wanted to access the intermediate kernel stack frames.
To know the status of the frame and the point of failure.<o:p></o:p></p>
<p class=MsoNormal style='margin-left:9.0pt'>When I tried to access a stack
frame I get an error message “<b>crash: prohibited gdb command: frame</b>”.
Can you please let me know if there is any other way of accessing
the kernel stack frames using crash. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>2) When I run bt in crash, I get a stack trace. Another person
from a different team reported a slightly different stack trace to mine. Below
are the stack traces. The register contents are quite different between the two<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>My stack trace<o:p></o:p></p>
<p class=MsoNormal><b>PID: 13366 TASK: ffff88031b60d580 CPU:
1 COMMAND: "telnet"<o:p></o:p></b></p>
<p class=MsoNormal><b> #0 [ffff88031ce759d0] machine_kexec at
ffffffff81024486<o:p></o:p></b></p>
<p class=MsoNormal><b> #1 [ffff88031ce75a40] crash_kexec at
ffffffff8107e230<o:p></o:p></b></p>
<p class=MsoNormal><b> #2 [ffff88031ce75b20] oops_end at ffffffff8100fa38<o:p></o:p></b></p>
<p class=MsoNormal><b> #3 [ffff88031ce75b50] no_context at
ffffffff8102d801<o:p></o:p></b></p>
<p class=MsoNormal><b> #4 [ffff88031ce75ba0] __bad_area_nosemaphore at
ffffffff8102d9c9<o:p></o:p></b></p>
<p class=MsoNormal><b> #5 [ffff88031ce75c70] bad_area at ffffffff8102da41<o:p></o:p></b></p>
<p class=MsoNormal><b> #6 [ffff88031ce75ca0] do_page_fault at
ffffffff8102dd19<o:p></o:p></b></p>
<p class=MsoNormal><b> #7 [ffff88031ce75cf0] page_fault at
ffffffff812d7425<o:p></o:p></b></p>
<p class=MsoNormal><b> #8 [ffff88031ce75d78] n_tty_read at
ffffffff811f03b3<o:p></o:p></b></p>
<p class=MsoNormal><b> #9 [ffff88031ce75ec0] tty_read at ffffffff811ebf7e<o:p></o:p></b></p>
<p class=MsoNormal><b>#10 [ffff88031ce75f10] vfs_read at ffffffff810ebcc8<o:p></o:p></b></p>
<p class=MsoNormal><b>#11 [ffff88031ce75f40] sys_read at ffffffff810ebe48<o:p></o:p></b></p>
<p class=MsoNormal><b>#12 [ffff88031ce75f80] system_call_fastpath at
ffffffff8100bbc2<o:p></o:p></b></p>
<p class=MsoNormal><b> RIP: 00007ffff716b9e0 RSP:
00007fffffffdfc0 RFLAGS: 00010212<o:p></o:p></b></p>
<p class=MsoNormal><b> RAX: 0000000000000000 RBX:
ffffffff8100bbc2 RCX: 0000000000000000<o:p></o:p></b></p>
<p class=MsoNormal><b> RDX: 0000000000001ff6 RSI:
000000000061c02a RDI: 0000000000000000<o:p></o:p></b></p>
<p class=MsoNormal><b> RBP: 0000000000001ff6 R8:
0000000000000000 R9: 0000000000000000<o:p></o:p></b></p>
<p class=MsoNormal><b> R10: 0000000000616680 R11:
0000000000000246 R12: 0000000000000000<o:p></o:p></b></p>
<p class=MsoNormal><b> R13: 0000000000000001 R14:
000000000061c02a R15: 00000000006178a0<o:p></o:p></b></p>
<p class=MsoNormal><b> ORIG_RAX: 0000000000000000 CS:
0033 SS: 002b<o:p></o:p></b></p>
<p class=MsoNormal><b><o:p> </o:p></b></p>
<p class=MsoNormal><b><o:p> </o:p></b></p>
<p class=MsoNormal>Reported stack trace <o:p></o:p></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>PID:
13366 TASK: ffff88031b60d580 CPU: 1 COMMAND:
"telnet"<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #0
[ffff88031ce759d0] machine_kexec at ffffffff81024486<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #1
[ffff88031ce75a40] crash_kexec at ffffffff8107e230<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #2
[ffff88031ce75ad8] n_tty_read at ffffffff811f03b3<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #3
[ffff88031ce75b20] oops_end at ffffffff8100fa38<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #4
[ffff88031ce75b50] no_context at ffffffff8102d801<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #5
[ffff88031ce75ba0] __bad_area_nosemaphore at ffffffff8102d9c9<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #6
[ffff88031ce75c20] native_sched_clock at ffffffff810120aa<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #7
[ffff88031ce75c70] bad_area at ffffffff8102da41<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #8
[ffff88031ce75ca0] do_page_fault at ffffffff8102dd19<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> #9
[ffff88031ce75cf0] page_fault at ffffffff812d7425<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
[exception RIP: n_tty_read+1420]<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
RIP: ffffffff811f03b3 RSP: ffff88031ce75da8 RFLAGS: 00010246<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
RAX: 0000000000000000 RBX: ffff8802cbd54a68 RCX: 000000000061c044<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
RDX: 0000000000000005 RSI: ffff88031ce75e87 RDI: ffff8802cbd54d1c<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
RBP: ffff88031ce75eb8 R8: 0000000000000000 R9:
0000000000000000<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
R10: 0000000000616680 R11: 0000000000000246 R12: 000000000061c044<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
R13: ffff8802cbd54800 R14: 0000000000000000 R15: 7fffffffffffffff<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #10 [ffff88031ce75ec0]
tty_read at ffffffff811ebf7e<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>#11
[ffff88031ce75f10] vfs_read at ffffffff810ebcc8<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>#12
[ffff88031ce75f40] sys_read at ffffffff810ebe48<o:p></o:p></span></b></p>
<p class=MsoPlainText><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>#13
[ffff88031ce75f80] system_call_fastpath at ffffffff8100bbc2</span></b><b><span
style='font-family:"Calibri","sans-serif"'><o:p></o:p></span></b></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>3) I want to retrieve the address of a data structure in the
current context. How can it be done? I tried using <i>struct</i> command, but
it did not help<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>4) When I run the command readelf -a vmcore, I get an error
message <b>”readelf: Error: Not an ELF file - it has the wrong magic
bytes at the start.”<o:p></o:p></b></p>
<p class=MsoNormal><b><o:p> </o:p></b></p>
<p class=MsoNormal><b><o:p> </o:p></b></p>
<p class=MsoNormal>Please help regarding the above queries. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks and Regards<o:p></o:p></p>
<p class=MsoNormal>Shashidhara<o:p></o:p></p>
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