Red Hat ENTERPRISE 5.4 RELEASE NOTES, Manual

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RHBA-2009:1283: bug fix update
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• The bt command displays a task's kernel-stack backtrace. When running this command against
an x86 Xen kernel vmcore, crash did not correctly handle the transition from the IRQ stack back to
the process stack, leading to a segmentation fault. The version of crash provided with this advisory
contains a patch that corrects this issue, allowing users to analyze a vmcore file from a system with
an x86 Xen kernel.
All users of crash should upgrade to this updated package.
1.26.2. RHBA-2009:1283: bug fix update
Updated crash packages that resolve several issues are now available.
The crash packages are used to investigate live systems and kernel core dumps created from the
netdump, diskdump and kdump facilities.
These updated crash packages are rebased to upstream version 4.0-8.9 (
BZ#494028
188
) and provide
fixes for the following bugs:
• if entered alone on the command line, the "set" command would cause a segmentation violation,
because there is no concept of a "context" in the Xen hypervisor. Crash now prompts the user to
provide an option with "set", and provides more meaningful error messages if the option selected is
not applicable. (
BZ#462819
189
)
• crash would indicate "irq: invalid structure size: gate_struct" and dump a stack trace leading to
x86_64_display_idt_table() when the "irq -d" option was run on AMD64 and Intel 64 Xen kernels.
Now it will indicate that the -d option is not applicable. (
BZ#464116
190
)
• the "bt" command did not work correctly when running against the Xen hypervisor binary. The "bt -o"
option, and setting it to run by default with "bt -O", would fail with the vmlinux-specific error message
"bt: invalid structure size: desc_struct" with a stack trace leading to read_idt_table(). Now, it will
display the generic error message "bt: -o option not supported or applicable on this architecture or
kernel". The "bt -e" or "bt -E" will also display the same error message, as opposed to the command
usage message. Lastly, the "bt -R" option would cause a segmentation violation; it has been fixed to
work as it was designed. (
BZ#464288
191
)
• when run on a Xen hypervisor in which the backtrace leads to either "process_softirqs" or
"page_fault", the "bt" command backtrace would indicate: "bt: cannot resolve stack trace". The
recovery code would then terminate the command with the nonsensical error message: "bt: invalid
structure size: task_struct". The command now properly terminates the backtrace. (
BZ#474712
192
,
BZ#466724
193
)
• when run against the Xen hypervisor where the number of physical cpus outnumber the
MAX_VIRT_CPUS value for the processor type, the "bt -a" command would fail after displaying
backtraces for the first 32 (MAX_VIRT_CPUS) pcpus with the the error message: "bt: invalid vcpu".
The command now shows backtraces for all pcpus. (
BZ#471790
194
)
• the "mod -[sS]" command would fail with the error message: "mod: cannot find or load object
file for <name> module" if the target module object filename contains both underscore and dash
characters. Crash now parses these filenames correctly. (
BZ#480136
195
)
• an existing Itanium INIT and MCA handler bug incorrectly writes the pseudo task's command
name in its comm[] name string such that the CPU number may not be part of the string. The "bt"
188
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=494028