tree 3fcf73c59ea6b570e99ee284dddc092dfe22b99f
parent 1455ac0e0c75a3ea5a2dbf027d4d51e32a7fdeaa
author Richard Cooper <richard.cooper@arm.com> 1638785983 +0000
committer Richard Cooper <richard.cooper@arm.com> 1652275670 +0000

misc: Update Dmesg dump for changes to printk in Linux v5.10+.

The Linux Kernel's printk mechanism and data structures were
overhauled in v5.10. This patch updates gem5's facility to dump the
kernel Dmesg buffer on kernel panic to account for these changes.

The new mechanism splits the Demsg ringbuffer into three separate
ringbuffers, one containing the message data, one containing
descriptors used for lock-free synchronisation, and one containing the
message infos. For a detailed description please see the header of
`kernel/printk/printk_ringbuffer.c` in the Linux source code.

The new gem5 implementation tests for the correct version to
run (pre-v5.10 or post-v5.10) by testing for the presence of symbols
in the kernel. The new, post-v5.10 dump code is templated on types
compatible with the kernel's atomic_long_t to account for differences
between the 64-bit and 32-bit Linux kernels.

Because the new Dmesg buffer dump code in gem5 is intended for
disaster recovery, it intentionally prints the full Dmesg buffer with
minimal checking of the validity of the messages. Partially finished
and/or uncommitted messages will be printed along with the finalised
messages.

Change-Id: I62ac20735e0679f1ba2062ca7bb13692a5ca1eae
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59509
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>