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Old 05-21-2010, 04:12 PM
Dave Anderson
Default crash version 5.0.4 is available

- Fix for the x86 "bt" command when a newly-forked task's resumption
EIP address value is set to the "ret_from_fork" entry point by
copy_thread(). Without the patch, the backtrace attempt would
display "bt: cannot resolve stack trace", dump the text symbols on
the stack, and a possible USER-MODE exception frame.

- Fix for the x86 "bt" command if the kdump-generated NMI interrupts
a task running in kernel space at a point in the system_call entry
point code prior to the call to a system call function. Without the
patch, the backtrace attempt would display "bt: cannot resolve stack
trace", dump the text symbols on the kernel stack, and display any
"KERNEL-MODE" exception frames followed by a possible "USER-MODE"
exception frame.

- Fix for the "bt" command on 2.6.29 and later x86_64 kernels to
recognize and display exception frames generated by exceptions that
do not result in a stack switch, such as general protection faults.
Without the patch, the backtrace would potentially not display the
exception frames because the "error_exit" assembly-code label in
entry_64.S was replaced by the error_exit() entry point.

- The kernel patch for ppc64 CONFIG_SPARSEMEM_VMEMMAP kernels that
stores vmemmap page mapping information so that the crash utility
is able to translate vmemmap'd kernel virtual addresses has been
updated. The crash utility patch that was (preemptively) applied
in 5.0.2 for the initial kernel patch needs this update.

- Fix the error message for the "dev -p" comand when run on 2.6.26
or later kernels, which no longer have the global "pci_devices"
list head. The patch changes the message to show "dev: -p option
not supported or applicable on this architecture or kernel", instead
of the misleading "dev: no PCI devices found on this system" message.

- If a cpu in an s390 or s390x dumpfile is offline, and the "bt"
command receives a backtrace request for the "swapper" task on that
cpu, the command will display "CPU offline".

- Fix for 2.6.34 and later x86_64 kernels which generate per-cpu
symbols of type 'd' or type 'D' instead of type 'V'. Without the
patch, an x86_64 crash session fails during initialization with the
error message "crash: cannot determine idle task addresses from
init_tasks[] or runqueues[]", followed by "crash: cannot resolve
init_task_union". It is unclear why some kernel builds result in
only type 'V' per-cpu symbols, whereas others result in in type 'd'
and 'D', so the patch accepts both.

- Fix to prevent a segmentation violation during initialization in
the x86_64_get_active_set() function by verifying that the array
of current tasks in machdep->machspec->current[] has actually been
allocated. Theoretically it should never be NULL, but in the
unlikely event that x86_64_per_cpu_init() fails to find the required
per-cpu symbols, it will return without allocating the array.

- Fix to support KVM dumpfiles created with "virsh dump" that create
"cpu" header sections using a QEMU CPU_SAVE_VERSION version greater
than the supported version of 9. Without the patch, the crash
session fails during initialization with the error message "crash:
qemu-load.c:501: cpu_init_load_64: Assertion `version_id >= 4 &&
version_id <= 9' failed." The patch now accepts CPU_VERSION_VERSION
values up to 12.

- Fix for x86_64 KVM dumpfiles created with "virsh dump" whose kernels
have a "_text" virtual address higher than __START_KERNEL_map.
Without the patch, the physical base address calculation fails,
making the dumpfile unusable.
(anderson@redhat.com, pbonzini@redhat.com)

- Implemented a new "map" command that is seen only when running with
KVM guest dumpfiles created with "virsh dump". The layout of this
dumpfile format does not allow the access of system memory in a
"random-access" manner. Therefore, during session initialization, a
potentially time-consuming dumpfile scan procedure is required to
create a physical-memory-to-file-offset memory map for use during the
session. The new "map" command allows the user to either append the
memory map to the end of the dumpfile, or to create a discrete memory
map file. In either case, the dumpfile scan will not be required
during subsequent sessions. The command's help page may be seen by
entering "crash -h map".

- Fix for an incorrect calculation of the physical base address of a
fully-virtualized x86_64 RHEL6 guest kernel running on a RHEL5 Xen
host. Without the patch, the session failed during initialization
with the error messages "crash: cannot determine base kernel version"
and "crash: vmlinux and vmcore do not match!"

- Fix for the "bt" command on inactive (blocked) tasks on 2.6.33 and
later x86_64 kernels, which have the "thread_return" symbol removed
from the embedded "switch_to" macro. Without the patch, when run on
blocked tasks, the command would fail with the error message "bt:
cannot resolve thread_return".

- Fix for the "bt" command on 2.6.33 and later x86 kernels, which moved
the "system_call" assembly function to the .kprobes.text section.
Without the patch, the command would typically display two invalid
stack frames, both indicating they were in "ia32_sysenter_target".

- Fix for a segmentation violation caused by the "extensions/trace.c"
extension module, as seen when running the "trace show -c <cpu>"
command from that module.

- Implemented a "trace dump -t" command for the "extensions/trace.c"
extension module. The module already has a "trace show" command
to show what events had happened before the system crashed, but it
is just 1000 lines of code and it is not as complete as the related
"trace-cmd report" command from trace-cmd(1). The new extension
module command generates a "trace.dat" file, which in turn can be
used by the "trace-cmd report" option of trace-cmd(1). So this
patch improves both the crash trace command and the trace-cmd(1)
as well, which can now handle ftrace even if the kernel crashed.

Download from: http://people.redhat.com/anderson

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