- Addresses FC7/upstream x86 kernels that have been configured such
that the vmlinux symbol values do not match their relocated values
when loaded. If CONFIG_PHYSICAL_START contains an value that is
greater then CONFIG_PHYSICAL_ALIGN, then this mismatch occurs.
Since the crash utility and its embedded gdb have always expected
that the compiled-in kernel symbol addresses are "real", the virtual
to physical translation fails, leading to an initialization-time
failure with the message: "crash: vmlinux and /dev/crash do not
match!" (/dev/mem or the dumpfile name may replace /dev/crash).
To deal with this issue, there are several alternatives:
1) Configure the kernel with CONFIG_PHYSICAL_START less than
or equal to CONFIG_PHYSICAL_ALIGN. Having done that, there
is no problem; the resultant vmlinux file will be loaded at
the address for which it was compiled, which has always
been the case.
2) Since /proc/kallsyms uses the same format as a System.map file,
and since it reflects the relocated symbol addresses, it
can be placed on the crash command line as if it were
a System.map file. (Note that the System.map file created
by these relocated kernels contains the same "wrong" symbol
values as the vmlinux file from which it was created.)
3) On a live system that has /proc/kallsyms (i.e., the kernel was
configured with CONFIG_KALLSYMS), this version of the crash
utility will replace/patch the vmlinux symbol values with those
seen in /proc/kallsyms. The relocation value will be displayed
as a WARNING message during initialization.
4) On a dumpfile, the relocation will not be performed automatically
as on a live system. It will require the addition of the
/proc/kallsyms on the command line, or if run on a different
host, a copy of the crashed system's /proc/kallsyms may be
used.
5) Alternatively on a dumpfile, a new command line option has been
created to specify the relocation amount. For example, if a
kernel was configured with a CONFIG_PHYSICAL_START value of 16MB
and a CONFIG_PHYSICAL_ALIGN of 4MB, that results in a relocation
of 12MB. To specify that, enter "crash --reloc=12m ..." on the
command line. (Recall that if crash is run on the live system,
a WARNING message will specify the relocation amount.)
Using /proc/kallsyms or a --reloc=[size] as a command line argument
is similar to using a System.map file, in that it results in the loss
of the use of line number debug data. (anderson@xxxxxxxxxx)
- Fix for x86 2.6.22 kernel initialization-time failure indicating:
"crash: invalid size request: 0 type: __per_cpu_offset"
(oomichi@xxxxxxxxxxxxxxxxx)
- Fix to recognize the 2.6.22 kernel's replacement of kmalloc slab
subsystem from the "./mm/slab.c" file to CONFIG_SLUB-configured
kernels that use the infrastructure in "./mm/slub.c". Without this
fix, crash sessions would fail during initialization with the message
"crash: invalid structure member offset: kmem_cache_s_c_num".
(anderson@xxxxxxxxxx)
- Cliff Wickman sent an additional patch for the LKCD kerntypes
support he introduced in version 4.0-4.4, which addresses this
message that is seen during initialization on 2.6.22 kernels:
"WARNING: cannot determine pgdat list for this kernel/architecture".
(cpw@xxxxxxx)
- NOTE: The CONFIG_SLUB change in the 2.6.22 kernel will require a
significant update in the crash utility in order for "kmem -[sS]"
options to work again.
- NOTE: 2.6.22 kernels have replaced the O(1) scheduler with the
new CFS scheduler. As a result, the "runq" command fails, which
will require a crash utility update to recognize and display the
contents of each cpu's run queue.
Download from: http://people.redhat.com/anderson
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