On Sun, Nov 20, 2016 at 10:32:50AM -0800, Linus Torvalds wrote: > On Sun, Nov 20, 2016 at 5:21 AM, Russell King - ARM Linux > <li...@armlinux.org.uk> wrote: > > On Tue, Oct 25, 2016 at 07:32:00PM +1100, Nicholas Piggin wrote: > >> > >> Michal, what's your thoughts? If you merge my patch 2/2 and skip 1/2, it > >> should not give any new build warnings or errors, so then arch patches can > >> go via arch trees. 1/2 could go in after everyone is up to date. > > > > So what's the conclusion on this? I've just had a failure due to > > CONFIG_TRIM_UNUSED_KSYMS reported on ARM, and it looks like (at > > least some of) patch 1 could resolve it. > > Hmm. I've got > > cc6acc11cad1 kbuild: be more careful about matching preprocessed asm > ___EXPORT_SYMBOL > 4efca4ed05cb kbuild: modversions for EXPORT_SYMBOL() for asm > > in my tree. Is that sufficient, or do we still have issues?
Hmm, those seem to have gone in during the last week, so I haven't tested it yet (build running, but it'll take a while). However, I don't think they'll solve _this_ problem. Some of the issue here is that we use a mixture of assembly macros and preprocessor for the ARM bitops - the ARM bitops are created with an assembly macro which contains some pre-processor expanded macros (eg, EXPORT_SYMBOL()). This means that the actual symbol being exported is not known to the preprocessor, so doing the "__is_defined(__KSYM_##sym)" inside "EXPORT_SYMBOL(\name)" becomes "__is_defined(__KSYM_\name)" to the preprocessor. As "__KSYM_\name" is never defined, it always comes out as zero, hence we always use __cond_export_sym_0, which omits the symbol export from the assembly macro definition: .macro bitop, name, instr .globl \name ; .align 0 ; \name: ... .type \name, %function; .size \name, .-\name .endm In other words, using preprocessor macros inside an assembly macro may not work as expected, and now leads to config-specific failures. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
