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Old 03-30-2011, 08:38 PM
Dave Anderson
Default crash version 5.1.4 is available

- Fix for RT kernels in which the schedule() function has become a
wrapper function that calls the __schedule() function, and where
other functions may call __schedule() directly. Without the patch,
a warning message indicating "crash: cannot determing thread return
address" is displayed during invocation on x86_64 machines, and
backtraces of blocked tasks may have missing or invalid frames.

- Fix for running against live x86 kernels that were configured with
CONFIG_PHYSICAL_START containing a value that is greater than its
CONFIG_PHYSICAL_ALIGN value, and where the first symbol listed by
/proc/kallsyms is not "_text". Without the patch, the crash session
fails during invocation with the error message "crash: vmlinux and
/dev/mem do not match!" (or "/dev/crash" if applicable). As a work-
around, "/proc/kallsyms" can be entered on the command line, or the
"--reloc=<size>" option could be used, but the fix obviates that
requirement for live systems. It should be noted that dumpfiles of
kernels configured that way still do require that "/proc/kallsyms",
or a copy of it, or alternatively the "--reloc=<size>" option, to
be entered on the command line, as detailed in this changelog entry:

- Unlike other extension modules, the "sial.so" module must be built
within a pre-built crash source tree because it uses header files
from the embedded gdb module. Therefore if a crash source tree is
laid down, entered, and "make extensions" is entered without first
building the crash utility, the build of sial.so build spews numerous
error messages. To avoid that, the sial.mk file has been modified to
check whether the embedded gdb build has been completed, and if it
has not, just displays "sial.so: build failed: requires the crash
gdb-7.0 module".

- If an extension module does not have its own <module>.mk file,
and is built using the extensions/Makefile, then it will be compiled
with the -Wall flag.

- The "trace.so" extension module has been improved to use "trace.cmd"
to implement the "trace show" option, instead of maintaining a
redundant code base within the module itself. The trace-cmd command
is better, mature, and continually maintained. The new "trace show"
option works like so:
(1) builds trace.dat from the core file and dumps it to /tmp.
(2) execs "trace-cmd report" upon the trace.dat file.
(3) splices the output of trace-cmd to the user and unlinks the
temporary file.

- Updates to the "trace.so" extension module to extract trace_bprintk()
formats from a kernel core dump. It handles both the current format
and a new format that will be pushed out after the merge window has
closed for Linux 2.6.40. The new format is required for the kernel
debugfs to export the same bprintk data as well. This means that the
trace.so extension module will be able to extract more information
than trace-cmd itself can on a running kernel.

- Fix for the "gdb" command, or any command that resolves to a gdb
command, to not strip quotation marks from the input line. Without
the patch, any gdb command whose arguments contain quotation marks,
(e.g. "printf") would fail because they get incorrectly stripped
from the input line.

- Fix for the "p" command if its symbolic argument is a "char *" that
points to a static data string containing an "%" character. Without
the patch, the command results in a segmentation violation.

- Fix for the "sys -c" option to display an error message if a known
sys_call_table entry is not a valid system call address. Without
the patch, the compromised system call entry is not displayed unless
the crash debug mode is set to 1 or greater. With the patch, the
system call number will be followed by an error message indicating
"invalid sys_call_table entry: <address> (<symbol-name>)". This
change is only applicable on architectures/kernels where the index of
the sys_call_table array can be confirmed by debuginfo data, i.e.,
is not a loose calculation based upon the next kernel symbol.

- Print a warning message if there is any inconsistency between the
kernel version strings found in the vmlinux file vs. the dumpfile
or live memory. If a System.map file is used to correct the virtual
addresses found in the vmlinux file, the message is not displayed.

- Fix for "kmem -v", and all other commands that search through the
kernel's mapped virtual address list, in x86_64 kernel versions from
2.6.0 to 2.6.11. Those kernels contained a "vmlist" and a separate
"mod_vmlist" list header, both of which point to list of vm_structs
that described each contiguous block of mapped kernel memory. 2.6.12
and later x86_64 kernels consolidated both lists onto the "vmlist".
Without the patch, the list headed by "mod_vmlist" was not searched.

- Clarify the help page documentation for the "struct -l offset" option
so that it does not imply that the address argument is necessarily
an embedded list_head pointer. The "-l offset" option essentially
provides the capability of the kernel's container_of() macro, such
that the address of an embedded data structure can be used to display
its containing data structure.

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

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