| Message ID | 20171103171203.107569-10-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Sami, Very interesting reading, thank you. On Fri, Nov 03, 2017 at 10:11:53AM -0700, Sami Tolvanen wrote: > This change fixes the following error message when linking with GNU > gold: > > ld.gold: error: unrecognized emulation aarch64linux > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > --- > arch/arm64/Makefile | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index eb6f3c9ec6cb..c16bd1ab37f8 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -64,14 +64,18 @@ KBUILD_CPPFLAGS += -mbig-endian > CHECKFLAGS += -D__AARCH64EB__ > AS += -EB > LD += -EB > +ifneq ($(ld-name),gold) > LDFLAGS += -maarch64linuxb > +endif > UTS_MACHINE := aarch64_be > else > KBUILD_CPPFLAGS += -mlittle-endian > CHECKFLAGS += -D__AARCH64EL__ > AS += -EL > LD += -EL > +ifneq ($(ld-name),gold) > LDFLAGS += -maarch64linux > +endif > UTS_MACHINE := aarch64 > endif -maarch64linux was added to LDFLAGS, and -mabi=lp64 was added to CFLAGS at the same patch to ensure that kernel will be compiled and linked in lp64 mode, even if toolchain by default compiles and links targets in ilp32 mode. So I think that simple removing this flag looks inaccurate. Also, IIUC, this patch is not related to LTO, because if ld.gold doesn't recognize -maarch64linux with LTO, it will not recognize it in non-LTO build. Am I right? I think that more correct way to do it would be either: - add maarch64linux to ld.gold, if possible. In discussion to other patches people talk that they need very fresh clang to build kernel properly, so this may be considered as similar issue; - if ld.gold understands some synonyms like -mabi=lp64, it should be passed to LDFLAGS here; - if ld.gold can link only lp64 objects, it should be commented here. But in this case I don't understand for example how to build vdso for ilp32 userspace... Thanks, Yury
On Fri, Nov 03, 2017 at 11:41:57PM +0300, Yury Norov wrote: > Also, IIUC, this patch is not related to LTO, because if ld.gold doesn't > recognize -maarch64linux with LTO, it will not recognize it in non-LTO > build. Am I right? That's correct. ld.gold --help says -m is obsolete, but at the same time, it supports a number of emulations, just with different names than ld.bfd. I'll take a closer look at this and see if there's a different flag we should be passing here instead. Looks like I also have some 0-day issues to address for v2. Sami
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index eb6f3c9ec6cb..c16bd1ab37f8 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -64,14 +64,18 @@ KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__ AS += -EB LD += -EB +ifneq ($(ld-name),gold) LDFLAGS += -maarch64linuxb +endif UTS_MACHINE := aarch64_be else KBUILD_CPPFLAGS += -mlittle-endian CHECKFLAGS += -D__AARCH64EL__ AS += -EL LD += -EL +ifneq ($(ld-name),gold) LDFLAGS += -maarch64linux +endif UTS_MACHINE := aarch64 endif
This change fixes the following error message when linking with GNU gold: ld.gold: error: unrecognized emulation aarch64linux Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- arch/arm64/Makefile | 4 ++++ 1 file changed, 4 insertions(+)