On 04/09/2023 06:05, Linu Cherian wrote: > This RFC v3 patch series is rebased on v6.5-rc7 and is dependent > on the below two patches. [...] > > Steps for reading trace data captured in previous boot > ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1. cd /sys/bus/coresight/devices/tmc_etrXX/ > > 2. Change to special mode called, read_prevboot. > > #echo 1 > read_prevboot > > 3. Dump trace buffer data to a file, > > #dd if=/dev/tmc_etrXX of=~/cstrace.bin Hi Linu, I left this comment on V2, but I tested it again and get the same result. Instead of linking it I'll just re-paste it here: I made a reserved region, but when I run this command I get "Unable to handle kernel paging request at virtual address 001f1921ed10ffae". Is there an extra step involved if there was no trace captured from a previous panic? I thought I'd just be able to read out uninitialised data. Or is it the uninitialised metadata that's causing this issue? Also that's without KASAN or lockdep turned on. If I have a kernel with either of those things I get a different warning for each one. I expect the lockdep one would happen even in the working scenario though? > > 4. Reset back to normal mode > > #echo 0 > read_prevboot >
