On Wed, Mar 16, 2022 at 9:17 AM David Wysochanski <dwysocha@xxxxxxxxxx> wrote: > > On Mon, Mar 14, 2022 at 12:04 PM Philipp Rudo <prudo@xxxxxxxxxx> wrote: > > > > Hi, > > > > dumping the dmesg can cause an endless loop for the old prink mechanism (> > > v3.5.0 and < v5.10.0) when the log_buf got corrupted. This series fixes those > > cases by adding a cycle detection. The cycle detection is implemented in a > > generic way so that it can be reused in other parts of makedumpfile. > > > > Thanks > > Philipp > > > > v2: > > * Rename 'idx' to 'ptr' > > * Also print the non-loop part when a cycle was detected. Such a > > situation can happen when log_buf wrapped around in the kernel > > (log_first_idx != 0) and the corruption occurred on an > > idx < log_first_idx. > > * Add patch 4 fixing a bug independent from the memory corruption but > > found while investigating it. > > > > Philipp Rudo (4): > > makedumpfile: add generic cycle detection > > makedumpfile: use pointer arithmetics for dump_dmesg > > makedumpfile: use cycle detection when parsing the prink log_buf > > makedumpfile: print error when reading with unsupported compression > > > > Makefile | 2 +- > > detect_cycle.c | 99 +++++++++++++++++++++++++++++++++++++ > > detect_cycle.h | 40 +++++++++++++++ > > makedumpfile.c | 131 ++++++++++++++++++++++++++++++++++++++++--------- > > 4 files changed, 247 insertions(+), 25 deletions(-) > > create mode 100644 detect_cycle.c > > create mode 100644 detect_cycle.h > > > > -- > > 2.35.1 > > > > Thanks for doing v2. Reviewing / testing this now... You can add Reviewed-and-tested-by: Dave Wysochanski <dwysocha@xxxxxxxxxx> I tested this patchset against a large set of vmcores comparing output of "makedumpfile --dump-dmesg" with existing makedumpfile (kexec-tools-2.0.20-46.el8_4.3.x86_64) with the latest upstream plus these patches. No difference in output was seen. As advertised, this handles the loop condition when log_buf is corrupted. And with the v2 version of patch 3, the dmesg output is the same as "crash log" on the same vmcore. Also verified patch #4 works as advertised - thanks for including a better error message there for users. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
