Commit-ID: ef1b893c29d0dba778f67ad97b554b37f9108dcc Gitweb: http://git.kernel.org/tip/ef1b893c29d0dba778f67ad97b554b37f9108dcc Author: Andi Kleen <a...@linux.intel.com> AuthorDate: Sat, 8 Feb 2014 09:01:08 +0100 Committer: H. Peter Anvin <h...@linux.intel.com> CommitDate: Thu, 13 Feb 2014 20:24:13 -0800
lto, workaround: Add workaround for initcall reordering Work around a LTO gcc problem: when there is no reference to a variable in a module it will be moved to the end of the program. This causes reordering of initcalls which the kernel does not like. Add a dummy reference function to avoid this. The function is deleted by the linker. This replaces a previous much slower workaround. Thanks to Jan "Honza" Hubička for suggesting this technique. Suggested-by: Jan Hubička <hubi...@ucw.cz> Signed-off-by: Andi Kleen <a...@linux.intel.com> Link: http://lkml.kernel.org/r/1391846481-31491-4-git-send-email...@linux.intel.com Signed-off-by: H. Peter Anvin <h...@linux.intel.com> --- include/linux/init.h | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/include/linux/init.h b/include/linux/init.h index e168880..a3ba270 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -163,6 +163,23 @@ extern bool initcall_debug; #ifndef __ASSEMBLY__ +#ifdef CONFIG_LTO +/* Work around a LTO gcc problem: when there is no reference to a variable + * in a module it will be moved to the end of the program. This causes + * reordering of initcalls which the kernel does not like. + * Add a dummy reference function to avoid this. The function is + * deleted by the linker. + */ +#define LTO_REFERENCE_INITCALL(x) \ + ; /* yes this is needed */ \ + static __used __exit void *reference_##x(void) \ + { \ + return &x; \ + } +#else +#define LTO_REFERENCE_INITCALL(x) +#endif + /* initcalls are now grouped by functionality into separate * subsections. Ordering inside the subsections is determined * by link order. @@ -175,7 +192,8 @@ extern bool initcall_debug; #define __define_initcall(fn, id) \ static initcall_t __initcall_##fn##id __used \ - __attribute__((__section__(".initcall" #id ".init"))) = fn + __attribute__((__section__(".initcall" #id ".init"))) = fn; \ + LTO_REFERENCE_INITCALL(__initcall_##fn##id) /* * Early initcalls run before initializing SMP. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
