On Wed, 2020-02-19 at 11:00:07 UTC, Michael Ellerman wrote: > In xmon we have two variables that are used by the dump commands. > There's ndump which is the number of bytes to dump using 'd', and > nidump which is the number of instructions to dump using 'di'. > > ndump starts as 64 and nidump starts as 16, but both can be set by the > user. > > It's fairly common to be pasting addresses into xmon when trying to > debug something, and if you inadvertently double paste an address like > so: > > 0:mon> di c000000002101f6c c000000002101f6c > > The second value is interpreted as the number of instructions to dump. > > Luckily it doesn't dump 13 quintrillion instructions, the value is > limited to MAX_DUMP (128K). But as each instruction is dumped on a > single line, that's still a lot of output. If you're on a slow console > that can take multiple minutes to print. If you were "just popping in > and out of xmon quickly before the RCU/hardlockup detector fires" you > are now having a bad day. > > Things are not as bad with 'd' because we print 16 bytes per line, so > it's fewer lines. But it's still quite a lot. > > So shrink the maximum for 'd' to 64K (one page), which is 4096 lines. > For 'di' add a new limit which is the above / 4 - because instructions > are 4 bytes, meaning again we can dump one page. > > Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Applied to powerpc next. https://git.kernel.org/powerpc/c/d64c7dbb4d98306b794401ca924ad053f84b59f8 cheers
