On Wed, Nov 07, 2018 at 07:42:46PM +0100, Artem Savkov wrote: > On Wed, Nov 07, 2018 at 11:08:56AM -0600, Josh Poimboeuf wrote: > > On Wed, Nov 07, 2018 at 03:05:59PM +0100, Artem Savkov wrote: > > > The way it is currently done it is possible for read_symbols() to find the > > > same symbol as parent for ".cold" functions. > > > > I seem to remember having this discussion for kpatch-build, but I forget > > the details. Can you explain how this can happen (and also add that > > detail to the commit message)? > > find_symbol_by_name() traverses the same lists as read_symbols and when > we change sym->name in place without copying it it changes in the list > as well. So if child function is before parent in sec->symbol_list the > same function will be returned as "parent".
Ah, I see. > It is hard for me to put it into words worthy to be included into > commit message. The above description made sense to me, so it sounds like you're on the right path :-) > > I haven't seen any bug reports, is it purely theoretical? > > No, 4.20-rc1 (actually anything after 4a60aa05a063 "objtool: Support > per-function rodata sections", before that add_switch_table() doesn't > seem to be called for those .cold. funcs) fails to build for mewith > KCFLAGS="-ffunction-sections -fdata-sections" because objtool is > segfaulting. If you only see it triggered with -ffunction-sections, that would be another useful nugget for the commit log. Also, if it's fixing a regression, be sure to add the 'Fixes' tag. Thanks! -- Josh