On Wed, Dec 20, 2017 at 2:00 PM, Arnd Bergmann <[email protected]> wrote:
> gcc-6.0 and later marks support for ARMv3 and ARMv4 as 'deprecated', > meaning that this is expected to be removed at some point in the future, > with gcc-8.0 as the earliest. > > When building the kernel, the difference between ARMv4 and ARMv4T > is relatively small because the kernel never runs THUMB instructions > on ARMv4T and does not need any support for interworking. > > For any future compiler that does not support -march=armv4, we now > fall back to -march=armv4t as the architecture level selection, > but keep using -march=armv4 by default as long as that is supported > by the compiler. > > Similarly, the -mtune=strongarm110 and -mtune=strongarm1100 options > will go away at the same time as -march=armv4, so this adds a check > to see if the compiler supports them, falling back to no -mtune > option otherwise. > > Compiling with -march=armv4t leads the compiler to using 'bx reg' > instructions instead of 'mov pc,reg'. This is not supported on > ARMv4 based CPUs, but the linker can work around this by rewriting > those instructions to the ARMv4 version if we pass --fix-v4bx > to the linker. This should work with binutils-2.15 (released > May 2004) or higher, and we can probably assume that anyone using > gcc-7.x will have a much more recent binutils version as well. > > However, in order to still allow users of old toolchains to link > the kernel, we only pass the option to linkers that support it, > based on a $(ld-option ...) call. I'm intentionally passing the > flag to all linker versions here regardless of whether it's needed > or not, so we can more easily spot any regressions if something > goes wrong. > > For consistency, I'm passing the --fix-v4bx flag for both the > vmlinux final link and the individual loadable modules. > The module loader code already interprets the R_ARM_V4BX relocations > in loadable modules and converts bx instructions into mov even > when running on ARMv4T or ARMv5 processors. This is now redundant > when we pass --fix-v4bx to the linker for building modules, but > I see no harm in leaving the current implementation and doing both. > > Signed-off-by: Arnd Bergmann <[email protected]> > --- > Please test by making the -march=armv4t switch unconditional > and see if that results in a working kernel I did this: diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 66e46aec0cd0..3944ecd6cd31 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -81,7 +81,7 @@ arch-$(CONFIG_CPU_32v6K) =-D__LINUX_ARM_ARCH__=6 $(call cc-option,-march=armv6k, endif arch-$(CONFIG_CPU_32v5) =-D__LINUX_ARM_ARCH__=5 $(call cc-option,-march=armv5te,-march=armv4t) arch-$(CONFIG_CPU_32v4T) =-D__LINUX_ARM_ARCH__=4 -march=armv4t -arch-$(CONFIG_CPU_32v4) =-D__LINUX_ARM_ARCH__=4 $(call cc-option,-march=armv4,-march=armv4t) +arch-$(CONFIG_CPU_32v4) =-D__LINUX_ARM_ARCH__=4 -march=armv4t arch-$(CONFIG_CPU_32v3) =-D__LINUX_ARM_ARCH__=3 -march=armv3 Built and booted on the Gemini platform. It crashes immediately and goes into the boot loader on thos FA-526 based platform. Yours, Linus Walleij
