> Hi Carlos, Dave & parisc-linux mailing list, > > I just started looking into implementing function tracer functionality > into the parisc kernel (http://cateee.net/lkddb/web-lkddb/FUNCTION_TRACER.html). > > While doing so, I noticed that gcc issues lots of warnings like this one: > CC arch/parisc/lib/iomap.o > cc1: warning: -ffunction-sections disabled; it makes profiling impossible > > So it seems that this statement in arch/parisc/Makefile: > # Without this, "ld -r" results in .text sections that are too big > # (> 0x40000) for branches to reach stubs. > cflags-y += -ffunction-sections > > breaks with the -pg compile option which is needed for function tracing. > > Some searching with google brought up this thread: > http://gcc.gnu.org/ml/gcc-help/2008-11/msg00128.html > and esp. this answer: > http://gcc.gnu.org/ml/gcc-help/2008-11/msg00141.html Hmmm, we killed named section support on the HP-UX SOM port several years ago because it wasn't very useful. Jeff did it... So, at this time, only Solaris is an issue. Of course, changing the code in toplev.c affects all targets. So, a change to remove this would have to go into 4.5 quite early. There was some work on the profiling implementation for both HP-UX and Linux after the removal of named section support on HP-UX, so the label issue may not be a problem. Remove the code disabling function sections when -pg is specified and see what happens. [I have thought it would be useful to have named sections for dwarf2 debug support on HP-UX. However, this is not useful for normal code. I have a patch somewhere to do this, but gdb needs work which I've never got around to. So, I might bring named section support back in a limited way.] Regarding .text sections that are too big, see this thread: http://sourceware.org/ml/binutils/2009-02/msg00061.html It seems that it should be possible to do more fine grained stub sections. At this time, it's not fully clear where the problem lies. GCC may need to start a new .text section before each function, or maybe the .text sections are getting merged. Recently, I got pushed to look a bit at GNU ld. It turns out there is no long branch stub support in it at all. As a result, it can't assemble large applications like cc1plus. It can just barely link cc1. It might have trouble with a large linux kernel. I added a check recently to generate an error if a branch target is out of range. There's a possibility that the current code for stub management in elf32-hppa.c can be modified for hppa64 without too much work. I don't know about the "ld -r" problem but I suspect we have to stop .text sections from getting merged in partial links. The other possiblity would be to add long branch stubs for calls to undefined symbols. The latter approach would complicate final links. Regards, Dave -- J. David Anglin dave.anglin@xxxxxxxxxxxxxx National Research Council of Canada (613) 990-0752 (FAX: 952-6602) -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
