diff options
| author | Andi Kleen <ak@linux.intel.com> | 2014-02-08 09:01:08 +0100 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2014-02-13 20:24:13 -0800 |
| commit | ef1b893c29d0dba778f67ad97b554b37f9108dcc (patch) | |
| tree | c77e509d240979f0718d6778a6abfe42fc0b59c3 | |
| parent | 128ea04a9885af9629059e631ddf0cab4815b589 (diff) | |
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 <hubicka@ucw.cz>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1391846481-31491-4-git-send-email-ak@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
| -rw-r--r-- | include/linux/init.h | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/include/linux/init.h b/include/linux/init.h index e1688802964f..a3ba27076342 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. |