On 06/15/2011 12:56 AM, Shashidhara Shamaiah wrote: > Hi, > > > > I was investigating a 64 bit linux kernel dump . I have following doubts > regarding usage of crash. > > > > 1) I wanted to access the intermediate kernel stack frames. To know the > status of the frame and the point of failure. > > When I tried to access a stack frame I get an error message "crash: > prohibited gdb command: frame". Can you please let me know if there is > any other way of accessing the kernel stack frames using > crash. > Try 'bt -f' Try also 'help bt' to discover other nice parameters as well. > > 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 > > > > My stack trace > > PID: 13366 TASK: ffff88031b60d580 CPU: 1 COMMAND: "telnet" > > #0 [ffff88031ce759d0] machine_kexec at ffffffff81024486 > > #1 [ffff88031ce75a40] crash_kexec at ffffffff8107e230 > > #2 [ffff88031ce75b20] oops_end at ffffffff8100fa38 > > #3 [ffff88031ce75b50] no_context at ffffffff8102d801 > > #4 [ffff88031ce75ba0] __bad_area_nosemaphore at ffffffff8102d9c9 > > #5 [ffff88031ce75c70] bad_area at ffffffff8102da41 > > #6 [ffff88031ce75ca0] do_page_fault at ffffffff8102dd19 > > #7 [ffff88031ce75cf0] page_fault at ffffffff812d7425 > > #8 [ffff88031ce75d78] n_tty_read at ffffffff811f03b3 > > #9 [ffff88031ce75ec0] tty_read at ffffffff811ebf7e > > #10 [ffff88031ce75f10] vfs_read at ffffffff810ebcc8 > > #11 [ffff88031ce75f40] sys_read at ffffffff810ebe48 > > #12 [ffff88031ce75f80] system_call_fastpath at ffffffff8100bbc2 > > RIP: 00007ffff716b9e0 RSP: 00007fffffffdfc0 RFLAGS: 00010212 > > RAX: 0000000000000000 RBX: ffffffff8100bbc2 RCX: 0000000000000000 > > RDX: 0000000000001ff6 RSI: 000000000061c02a RDI: 0000000000000000 > > RBP: 0000000000001ff6 R8: 0000000000000000 R9: 0000000000000000 > > R10: 0000000000616680 R11: 0000000000000246 R12: 0000000000000000 > > R13: 0000000000000001 R14: 000000000061c02a R15: 00000000006178a0 > > ORIG_RAX: 0000000000000000 CS: 0033 SS: 002b > > > > > > Reported stack trace > > PID: 13366 TASK: ffff88031b60d580 CPU: 1 COMMAND: "telnet" > > #0 [ffff88031ce759d0] machine_kexec at ffffffff81024486 > > #1 [ffff88031ce75a40] crash_kexec at ffffffff8107e230 > > #2 [ffff88031ce75ad8] n_tty_read at ffffffff811f03b3 > > #3 [ffff88031ce75b20] oops_end at ffffffff8100fa38 > > #4 [ffff88031ce75b50] no_context at ffffffff8102d801 > > #5 [ffff88031ce75ba0] __bad_area_nosemaphore at ffffffff8102d9c9 > > #6 [ffff88031ce75c20] native_sched_clock at ffffffff810120aa > > #7 [ffff88031ce75c70] bad_area at ffffffff8102da41 > > #8 [ffff88031ce75ca0] do_page_fault at ffffffff8102dd19 > > #9 [ffff88031ce75cf0] page_fault at ffffffff812d7425 > > [exception RIP: n_tty_read+1420] > > RIP: ffffffff811f03b3 RSP: ffff88031ce75da8 RFLAGS: 00010246 > > RAX: 0000000000000000 RBX: ffff8802cbd54a68 RCX: 000000000061c044 > > RDX: 0000000000000005 RSI: ffff88031ce75e87 RDI: ffff8802cbd54d1c > > RBP: ffff88031ce75eb8 R8: 0000000000000000 R9: 0000000000000000 > > R10: 0000000000616680 R11: 0000000000000246 R12: 000000000061c044 > > R13: ffff8802cbd54800 R14: 0000000000000000 R15: 7fffffffffffffff > > ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #10 > [ffff88031ce75ec0] tty_read at ffffffff811ebf7e > > #11 [ffff88031ce75f10] vfs_read at ffffffff810ebcc8 > > #12 [ffff88031ce75f40] sys_read at ffffffff810ebe48 > > #13 [ffff88031ce75f80] system_call_fastpath at ffffffff8100bbc2 > > > > > > 3) I want to retrieve the address of a data structure in the current > context. How can it be done? I tried using struct command, but it did > not help > You need to use bt -f and find what pointer you are looking for and then: struct <struct name> pointer most of times just doing: <struct name> pointer works out fbl > > 4) When I run the command readelf -a vmcore, I get an error message > "readelf: Error: Not an ELF file - it has the wrong magic bytes at the > start." > > > > > > Please help regarding the above queries. > > > > Thanks and Regards > > Shashidhara > > > Information transmitted by this e-mail is proprietary to MphasiS, its associated companies and/ or its customers and is intended > for use only by the individual or entity to which it is addressed, and may contain information that is privileged, confidential or > exempt from disclosure under applicable law. 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