On Monday, August 8, 2016 9:19:47 AM CEST Alan Modra wrote: > On Sun, Aug 07, 2016 at 10:26:19PM +0200, Arnd Bergmann wrote: > > On Sunday, August 7, 2016 7:27:39 PM CEST Alan Modra wrote: > > > > > > If it can, then Nicholas' patch should be: > > > > > > *(.text.hot .text.hot.*) *(.text.unlikely .text.unlikely.*) *(.text .text.*) > > > > > > If you can't put .text.fixup too far away then you may as well just use > > > > > > *(.text .text.*) > > > > I tried this version: > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > index b1f8828e9eac..fc210dacac9a 100644 > > --- a/include/asm-generic/vmlinux.lds.h > > +++ b/include/asm-generic/vmlinux.lds.h > > @@ -438,7 +438,9 @@ > > * during second ld run in second ld pass when generating System.map */ > > #define TEXT_TEXT \ > > ALIGN_FUNCTION(); \ > > - *(.text.hot .text .text.fixup .text.unlikely .text.*) \ > > + *(.text.hot .text.hot.*) \ > > + *(.text.unlikely .text.fixup .text.unlikely.*) \ > > + *(.text .text.*) \ > > *(.ref.text) \ > > MEM_KEEP(init.text) \ > > MEM_KEEP(exit.text) \ > > > > but that failed to link an allyesconfig kernel because of references > > from .fixup to .text.*. Trying your version now: > > Well then, that proves you can't put .text.fixup too far aways from > the associated input section. > > > *(.text.hot .text.hot.*) *(.text.unlikely .text.unlikely.*) *(.text .text.*) > > Which means this is guaranteed to fail when you test it properly using > gcc's profiling options, in order to generate .text.hot* and/or > .text.unlikely* sections. I've investigated further and it seems that "*(.text.fixup) *(.text .text.*)" fails just because we list .text.fixup twice. The .text.fixup section was originally[1] introduced to work around the same link error that it is causing now: if we use recursive linking, merging .text and .text.fixup helps avoid the problems of sections that are >32MB before the final link. I have reverted that patch now, so ARM uses ".fixup" again like every other architecture does, and now "*(.fixup) *(.text .text.*)" works correctly, while ""*(.fixup) *(.text .fixup .text.*)" also fails the same way that I saw before: drivers/scsi/sg.o:(.fixup+0x4): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0xc): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x14): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x1c): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x24): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x2c): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x34): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x3c): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' drivers/scsi/sg.o:(.fixup+0x44): relocation truncated to fit: R_ARM_THM_JUMP24 against `.text.sg_ioctl' I don't understand what led Andi Kleen to also move .text.hot and .text.unlikely together with .text [2], but this may have been a related issue. > It seems to me the right thing to do would be to change kernel asm to > generate .text.foo.fixup for any .text.foo section. A gas feature > available with binutils-2.26 enabled by --sectname-subst might help > with implementing that. I think this what Nico wanted to use anyway to eliminate more functions from the output. Arnd [1] http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8321 http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8322 [2] https://lkml.org/lkml/2015/7/19/377 -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
