backtraces of the active tasks start at the function that is saved
in each per-cpu ELF note. With the patch, the backtrace will start
at the "crash_kexec" function on the panicking cpu, and at the
"crash_save_cpu" function on the other active cpus. By doing so,
the backtrace will display the exception handling functions leading
to crash_kexec() or crash_save_cpu(), as well as the exception frame
register set as it was at the time of the fatal exception on the
panic cpu, or when the shutdown IPI was received on the other cpus.
(anderson@redhat.com)
and "vtop" commands. Without the patch, if "vm -p" references a
swapped-out page on Linux 4.0 and later kernels, the SWAP location
may indicate "(unknown swap location)", and will show an invalid
OFFSET value; on Linux 3.13 and later kernels, running "vtop" on a
user virtual address incorrectly translates the PTE contents of
swapped out pages by showing a PHYSICAL address and FLAGS translation
instead of the SWAP device and OFFSET. It is possible that there may
be PTE bit translation errors on other kernel versions; the patch
addresses the changes in ARM64 PTE bit definitions made in Linux
3.11, 3.13, and 4.0 kernels.
(anderson@redhat.com)
kernels. Without the patch, the crash session fails during
initialization with the message "crash: invalid/unsupported page
size: 98304" on kernels with 64K pages. On kernels with 4K pages,
the message is "crash: invalid/unsupported page size: 6144". In
addition, the "-p <page-size>" command line override option
had no effect on ARM64; that has been fixed as well.
(anderson@redhat.com)
layout introduced in Linux 3.17. The vmalloc region end address, and
the vmemmap start and end addresses are now calculated at kernel
build time, because they depend upon the size of a struct page.
Accordingly, the crash utility needs to calculate those three address
values dynamically, after the embedded gdb module has initialized.
Without the patch, reads of page structures return invalid data due
to incorrect virtual-to-physical translations of memory in the
vmemmap range. This in turn causes commands that require page
structure contents to fail or show invalid data, such as "kmem -p",
"kmem -[sS]", and the "kmem -[fF]" options.
(anderson@redhat.com)
symbols that are below the text region. Without the patch, several
recently-introduced absolute symbols have been introduced into the
kernel, which will be displayed by "sym -l" prior to the first kernel
virtual address symbol, and will show up in command output where
memory values are translated into kernel symbol references.
(anderson@redhat.com)
Without the patch, if certain patterns of cpus are offline, the count
may be too small, causing cpu-dependent commands to not recognize
online cpus.
(Jan.Karlsson@sonymobile.com, anderson@redhat.com)
the active tasks in the kernel's per-cpu crash_notes, there is an
initialization-time warning message indicating "could not retrieve
crash_notes". It has been changed to a more meaningful warning
message indicating "cannot retrieve registers for active tasks".
(anderson@redhat.com)
kernel's VA_BITS value. It currently is hardwired in the kernel to
one of two values depending upon whether 4K or 64K pages are
configured. However, there are plans to support 16K paqes, to make
VA_BITS a configurable value, and to make the number of page-table
levels configurable. Towards that end, the crash utility has been
changed to determine the VA_BITS value based upon known kernel
virtual addresses, and to then calculate the relevant kernel virtual
address ranges on that value instead of hardwiring them based upon
the page size.
(anderson@redhat.com)
extension module, do not attempt to read the crash_notes. Since the
dumpfile was taken while running on a live system, the crash_notes,
if configured into the kernel, would not contain valid data. Without
the patch, the message "WARNING: could not retrieve crash_notes" is
displayed during session initialization.
(anderson@redhat.com)
that begin with "__crc_". Without the patch, several thousand of
them may be displayed by "sym -l" prior to the first kernel virtual
address symbol.
(anderson@redhat.com)
with 64K pages if the address argument is located in the kernel
logical memory map region, which uses 512MB hugepage mappings.
Without the patch, the verbose page table walk mistakenly continues
to the PTE level.
(anderson@redhat.com)
properly translated to the filename and offset. Without the patch,
file-backed pages are erroneously shown as being backed on a swap
device.
(anderson@redhat.com)
structure addresses for kernels configured with 4K pages. Without
the patch, any command that required the contents of a page structure
would fail with a readmem error.
(cldu@marvell.com, anderson@redhat.com)
several command options still under development. In-kernel exception
frames are only dumped if the exception handler function is contained
within the symbol boundaries from "__exception_text_start" to
"__exception_text_end"; when ARM64 kdump is eventually implemented,
further exception-related work will be resumed.
(anderson@redhat.com)
kernels that expand to a 42-bit address space when 64K pages are
configured. This is also the first crash version that has been
tested on a live ARM64 system with 4K pages, where it cleanly
make it to the "crash>" prompt. However, it should be noted that
some commands (most notably "bt") still do not work as of yet.
(anderson@redhat.com)
