On Tue, 8 Aug 2017 10:53:56 +0900 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: > Hi Nicholas, > > 2017-07-26 21:46 GMT+09:00 Nicholas Piggin <npiggin@xxxxxxxxx>: > > The .data and .bss sections were modified in the generic linker script to > > pull in sections named .data.<C identifier>, which are generated by gcc with > > -ffunction-sections and -fdata-sections options. > > > > The problem with this pattern is it can also match section names that Linux > > defines explicitly, e.g., .data.unlikely. This can cause Linux sections to > > get moved into the wrong place. > > > > The way to avoid this is to use ".." separators for explicit section names > > (the dot character is valid in a section name but not a C identifier). > > However currently there are sections which don't follow this rule, so for > > now just disable the wild card by default. > > > > Example: http://marc.info/?l=linux-arm-kernel&m=150106824024221&w=2 > > > > Cc: <stable@xxxxxxxxxxxxxxx> # 4.9 > > Fixes: b67067f1176df ("kbuild: allow archs to select link dead code/data elimination") > > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> > > --- > > include/asm-generic/vmlinux.lds.h | 38 ++++++++++++++++++++++++++------------ > > 1 file changed, 26 insertions(+), 12 deletions(-) > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > index da0be9a8d1de..9623d78f8494 100644 > > --- a/include/asm-generic/vmlinux.lds.h > > +++ b/include/asm-generic/vmlinux.lds.h > > @@ -60,6 +60,22 @@ > > #define ALIGN_FUNCTION() . = ALIGN(8) > > > > /* > > + * LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections, which > > + * generates .data.identifier sections, which need to be pulled in with > > + * .data. We don't want to pull in .data..other sections, which Linux > > + * has defined. Same for text and bss. > > + */ > > +#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION > > +#define TEXT_MAIN .text .text.[0-9a-zA-Z_]* > > +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* > > +#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* > > +#else > > +#define TEXT_MAIN .text > > +#define DATA_MAIN .data > > +#define BSS_MAIN .bss > > +#endif > > > From the git-log, I think you are planning to rename > .data.unlikely -> .data..unlikey > then the problem will be fixed. > > ("git grep data.unlikely" gave me only 7 instances.) > > > Why is this patch necessary? > > > You are trying to migrate some architectures to DCDE, > so this #ifdef does not solve the problem, I think. Well basically I want to preserve previous behaviour and avoid regressions as far as possible. Patches to rename existing sections I think would not be so suitable for @stable. And there could be other things we've missed. Yes I would like to ensure all our sections use .. separators which (hopefully). Until then I think this is a minimal fix. Thanks, Nick