On Fri, Apr 23, 2021 at 12:45:14PM +0200, Jan Beulich wrote: > On 23.04.2021 12:07, Roger Pau Monné wrote: > > On Fri, Apr 23, 2021 at 10:51:40AM +0200, Jan Beulich wrote: > >> On 23.04.2021 09:30, Roger Pau Monné wrote: > >>> /* > >>> * Explicitly list debug section for the PE output so that they don't > >>> * end up at VA 0 which is below image base and thus invalid. Also use > >>> * the NOLOAD directive, even when currently ignored by PE output, in > >>> * order to note those sections shouldn't be loaded into memory. > >>> * > >>> * Note such sections are past _end, so if loaded will be discarded by > >>> * Xen anyway. > >>> */ > >>> > >>> Feel free to reword or expand the comment. > >> > >> Yes, I've edited it some while inserting. Will see to get to > >> submitting v2 then. > >> > >>> Not sure there's some > >>> reference we could add here about how debug sections are placed in PE > >>> files usually. > >> > >> As said before - I don't think there's any "usually" here, which is > >> why different environments have invented different ways. The debug > >> info native to COFF is more like ELF's symbol table (with a little > >> bit of extra information) plus Dwarf's .debug_line, but not really > >> fully covering what you'd expect from debug info. > > > > One last thing, do you know if the newly added debug_* sections get > > the IMAGE_SCN_MEM_DISCARDABLE section flag set? > > At least with an up-to-date ld (i.e. one meeting the requirements so > we wouldn't force debug info to be stripped) they do. > > > Not sure there's a way we can force it from the linker script TBH, but > > would be nice and seems to be a recommended flag for debug sections > > according to Microsoft [0]. > > The linker does this for debugging sections irrespective of what the > linker script says: > > if ((sec_flags & SEC_DEBUGGING) != 0) > styp_flags |= IMAGE_SCN_MEM_DISCARDABLE;
Great, that's good to know. Note sure it's worth adding to the commit message, maybe I've just missed part of the documentation where LD notes that IMAGE_SCN_MEM_DISCARDABLE will be unconditionally added to debug sections. Thanks, Roger.
