Hi Thomas, On Thu, 2016-10-27 at 11:24 +0200, Geert Uytterhoeven wrote: > On Thu, Oct 27, 2016 at 11:11 AM, Thomas Petazzoni > <thomas.petazzoni at free-electrons.com> wrote: > > > > On Thu, 27 Oct 2016 09:07:55 +0000, Alexey Brodkin wrote: > > > > > > > > > > > > > axs101 is using a 770 core, while the toolchain is built for the HS38 > > > > core. I'm somewhat surprised that a single ARC toolchain cannot produce > > > > code for both 770 and HS38, but it seems to be the case. > > > > > > > > So you need a separate toolchain for ARC770. > > > > > > Indeed axs101 uses ARC770 core which is ARCv1 AKA ARCompact ISA while > > > axs103 sports the same base-board but CPU daughter-card contains ARC HS38 core > > > which has ARCv2 ISA (binary incompatible with ARCompact). > > > > > > Essentially both gcc and binutils will happily build for both architectures given > > > proper options were passed on the command line. But Linux kernel gets linked with > > > pre-built libgcc (it is a part of toolchain). And so it all boils down to a requirement > > > to have multilibbed uClibc toolchain. Which we don't have. > > > > Interesting. Why is libgcc linked with the kernel on ARC? I don't think > > that's the case on other architectures: the kernel is freestanding and > > provides everything that it needs without relying on the compiler > > runtime. > > ARC is not the only one: > > $ git grep print-libgcc-file-name > arch/arc/Makefile:LIBGCC := $(shell $(CC) $(cflags-y) --print-libgcc-file-name) > arch/h8300/boot/compressed/Makefile:LIBGCC := $(shell > $(CROSS-COMPILE)$(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name) > arch/hexagon/Makefile:LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) > -print-libgcc-file-name) > arch/m32r/Makefile:LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) > -print-libgcc-file-name) > arch/nios2/Makefile:LIBGCC?????????:= $(shell $(CC) $(KBUILD_CFLAGS) > $(KCFLAGS) -print-libgcc-file-name) > arch/openrisc/Makefile:LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) > -print-libgcc-file-name) > arch/parisc/Makefile:LIBGCC = $(shell $(CC) $(KBUILD_CFLAGS) > -print-libgcc-file-name) > arch/tile/Makefile:??$(shell $(CC) $(KBUILD_CFLAGS) $(KCFLAGS) > -print-libgcc-file-name) > arch/xtensa/Makefile:LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) > -print-libgcc-file-name) > arch/xtensa/boot/boot-redboot/Makefile:LIBGCC := $(shell $(CC) > $(KBUILD_CFLAGS) -print-libgcc-file-name) Right. I'm not 100% sure about all the details in case of Linux kernel on ARC but I actually implemented decoupling from libgcc in U-Boot for ARC. And from that experience I know what was required out of libgcc, see http://git.denx.de/?p=u-boot.git;a=patch;h=a67ef280f46803e319639f5380ff8da6c6b7fbe7 And these are functions required by U-Boot (most probably the same is applied to kernel): 1) so-called millicode, stuff like?__ld_rX_to_rY,?__st_rX_to_rX 2) shifts: __ashldi3,?__ashrdi3,?__lshrdi3,? 3) divisions:?udivmodsi4,?__divsi3,?__modsi3,?__udivsi3,?__umodsi3 Indeed it is possible to have so-called private libgcc in kernel as well but benefit will be only for people building kernels but not user-space because in absence of multilibbed toolchain 2 separate toolchains will be required anyways. Still we'll have to pay an additional maintenance price to keep kernel's libgcc in sync with the one from gcc. -Alexey
