10:08 a.m.
- Versioning has been changed such that the crash-<version>.tar.gz
file no longer contains a "-" in the <version> number, and the
crash-<version>-0.src.rpm will always have a crash.spec release
number of "0". When the crash binary is built from the src.rpm file,
the "-0" will not be included/displayed as part of the crash binary's
version number, so that it will match the crash binary version that
is built from the crash-<version>.tar.gz file. This is being done
so that distributors can take the crash-<version>.tar.gz file
and append their own crash.spec file release numbering scheme onto
the base <version> number when creating their own src.rpm package.
(anderson(a)redhat.com)
- Wholesale replacement of the x86/x86_64 disassembly code in the
embedded gdb-6.1 module to that used in gdb-6.8. The primary motive
is for CONFIG_FUNCTION_TRACER kernels, which contain a 5-byte nopl
instructions that can be overwritten during runtime for dynamic
ftracing. That particular nop format was not recognized by the older
disassembly code in gdb-6.1, and printed a "(bad)" instruction
followed by a incorrect "add" instruction. For example, without the
patch, the instructions at sys_write+11 and sys_write+13 below are
not correct:
crash> dis sys_write
0xffffffff8113c56b <sys_write>: push %rbp
0xffffffff8113c56c <sys_write+1>: mov %rsp,%rbp
0xffffffff8113c56f <sys_write+4>: push %r12
0xffffffff8113c571 <sys_write+6>: push %rbx
0xffffffff8113c572 <sys_write+7>: sub $0x30,%rsp
0xffffffff8113c576 <sys_write+11>: (bad)
0xffffffff8113c578 <sys_write+13>: add %r8b,(%rax)
0xffffffff8113c57b <sys_write+16>: mov %rsi,%r12
...
With the patch, the 5-byte instruction is properly translated:
crash> dis sys_write
0xffffffff8113c56b <sys_write>: push %rbp
0xffffffff8113c56c <sys_write+1>: mov %rsp,%rbp
0xffffffff8113c56f <sys_write+4>: push %r12
0xffffffff8113c571 <sys_write+6>: push %rbx
0xffffffff8113c572 <sys_write+7>: sub $0x30,%rsp
0xffffffff8113c576 <sys_write+11>: nopl 0x0(%rax,%rax,1)
0xffffffff8113c57b <sys_write+16>: mov %rsi,%r12
...
There are other side-effects/changes such as the output of negative
relative offsets from registers. For example, without the patch,
instructions like this:
mov 0xffffffffffffffc8(%rbp),%rdx
are displayed in an easier-to-understand format:
mov -0x38(%rbp),%rdx
There are undoubtedly other subtle changes as well.
(anderson(a)redhat.com)
- Fix for compressed diskdump/kdump vmcores to properly handle
page descriptor structures that are located beyond a 4GB file
offset in the vmcore file.
(oomichi(a)mxs.nes.nec.co.jp)
- Fix for x86_64 "bt" command to properly recognize vsyscall FIXMAP
virtual addresses when encountered as the RIP in an exception frame.
Without the patch, the exception frame would be followed by the
warning message: "bt: WARNING: possibly bogus exception frame".
(anderson(a)redhat.com)
- Fix for the "sym <address>" command option when the address
references a symbol in the vsyscall FIXMAP virtual address page
in certain x86_64 kernel versions. Without the patch, the command
would fail with a "symbol not found" message. This would also affect
commands that perform symbolic translations of virtual addresses,
such as "rd -s".
(anderson(a)redhat.com)
- Fix for the x86_64 "bt" command that may possibly start the backtrace
of an active non-crashing task on its per-cpu IRQ stack instead of
starting from the NMI exception stack. This could only occur on
a kdump-generated vmcore, and as a result, the backtrace would make
a faulty transition back to the process stack, dump a bogus exception
frame, and display: "bt: WARNING: possibly bogus exception frame".
(anderson(a)redhat.com)
- Fix for the x86_64 "bt" command in determining the frame just above
an IRQ interrupt exception frame, or above an exception frame that
gets handled on the process stack, such as a page fault. Without
the patch, the frame size of the interrupted function was being
incorrectly calculated, and could result in the display of an invalid
stale frame just above the exception frame register dump.
(anderson(a)redhat.com)
- Fix for the x86_64 "bt" command's frame size calculating mechanism
to differentiate between text return addresses and the precise text
RIP address of an exception. Without the patch, the instruction of
the text return address location was being incorrectly scanned for
instructions that modify the frame size, and could result in the
skipping of a stack frame.
(anderson(a)redhat.com)
- Fix for usage of a System.map file argument with 2.6.30 and later
kernels (which only should be done if the vmlinux file does not match
the vmcore or live system being analyzed). Without the patch there
may be several hundred "crash: symbol count overflow (trace_kmalloc)"
messages displayed during the back-patching of the gdb minimal_symbol
table phase.
(anderson(a)redhat.com)
- Fix for usage of a System.map file argument whose symbol list does
not contain an "_end" symbol. Without the patch, the crash session
fails during initialization with the error message: "crash: cannot
resolve _end".
(anderson(a)redhat.com)
- Fix for "kmem -p <address>" or "kmem <address>" options
when the
<address> is not a page structure address. Without the patch,
starting with crash version 4.0-8.11, harmless but annoying "kmem:
WARNING: sparsemem: invalid section number: 8192" messages would be
displayed as a result of this patch.
(anderson(a)redhat.com)
- Fix for the snap.so extension module when run on pre-2.6.13 x86_64
kernels with more than 4GB of physical memory. Without the patch,
the resultant vmcore would not include memory above 4GB because
the /proc/iomem file did not display it. A typical crash session
would fail during initialization with an error message such as
"crash: read error: kernel virtual address: 1020009d024 type:
tss_struct ist array".
(anderson(a)redhat.com)
- Fix for the build of the sial.so extension module if /usr/bin/bison
and /usr/bin/flex do not exist on the host build system. When those
files do not exist, the build of sial.so generates a huge number of
error messages, ending with "make[3]: [sial.so] Error 1 (ignored)".
Since it is preferable to avoid extra BuildRequires entries in the
crash.spec file for extension modules, and given that it is often
built from a tar.gz installation, the failed build will indicate:
"sial.so: build failed: requires /usr/bin/flex and /usr/bin/bison".
(anderson(a)redhat.com)
- Fix for the build of the snap.so extension module on older systems
running with "make" versions 3.80 or earlier. Without the patch,
the build of snap.so would fail like so:
snap.mk:4: Extraneous text after `else' directive
snap.mk:7: Extraneous text after `else' directive
snap.mk:7: *** only one `else' per conditional. Stop.
make[2]: [snap.so] Error 2 (ignored)
The snap.mk file has been modified to conform to the older format.
(anderson(a)redhat.com)
- Fix for the "rd" and "vtop" commands on RHEL4 x86_64 Xen
paravirtual
kernels in the reading or translation of vmalloc addresses that are
not in kernel module vmalloc address space. In that kernel version
(and none other that I am aware of), the PAGE_OFFSET unity-map kernel
virtual address of 0xffffff8000000000 is larger than the address of
its VMALLOC_START, 0xffffff0000000000. Because of that, without the
patch, "rd" would fail with the error message "rd: invalid user
virtual address: <address> type: 64-bit UVADDR", "vtop" would
fail with the error message "vtop: ambiguous address: <address>
(requires -u or -k)", and "vtop -k" would incorrectly report that
the <address> was "(not a kernel virtual address)".
(anderson(a)redhat.com)
- Implemented a new "-x" command line option that will automatically
load extension modules from a particular directory. The search for
the extension module directory will be done in the following order,
and the first one (if any) that exists will be selected as the
target directory:
1. the directory specified in the CRASH_EXTENSIONS shell
environment variable
2. /usr/lib64/crash/extensions (64-bit architectures)
3. /usr/lib/crash/extensions
4. ./extensions
All extension modules that are found in the target directory will
be loaded automatically.
(anderson(a)redhat.com)
Download from: http://people.redhat.com/anderson