Linux helpfully complained about "register x18 corrupted by EFI" with the upcoming EFI loader support as this register is apparently the platform register and is meant to be usable by the OS without other firmware like the EFI runtime services clobbering it.
Provide a hidden AAPCS64 symbol that will be usable for this purpose. Signed-off-by: Ahmad Fatoum <[email protected]> --- arch/arm/Kconfig | 11 +++++++++++ arch/arm/Makefile | 1 + 2 files changed, 12 insertions(+) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index afa6de3cd0b1..d2d81a4f90d6 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -313,6 +313,17 @@ config AEABI To use this you need GCC version 4.0.0 or later. +config AAPCS64 + bool "Observe ARM64 Procedure Call Standard" if COMPILE_TEST + depends on CPU_V8 + help + This option instructs barebox to observe the AAPCS64 for + interoperability with other firmware. + + The only effect this currently has is reserving x18 (the + platform register), so Linux can call back into a barebox + EFI runtime service without it getting clobbered. + config THUMB2_BAREBOX select AEABI depends on !ARCH_TEGRA && !ARCH_AT91 diff --git a/arch/arm/Makefile b/arch/arm/Makefile index d6ae6b648f65..4d84f3bf9c72 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -68,6 +68,7 @@ CFLAGS_ABI-$(CONFIG_CPU_32) :=$(call cc-option,-mapcs-32,-mabi=apcs-gnu) $(call CFLAGS_ABI-$(CONFIG_AEABI) :=-mabi=aapcs-linux CFLAGS_ABI-$(CONFIG_ARM_UNWIND) +=-funwind-tables +CFLAGS_ABI-$(CONFIG_AAPCS64) +=-ffixed-x18 ifeq ($(CONFIG_THUMB2_BAREBOX),y) AFLAGS_AUTOIT :=$(call as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mauto-it) -- 2.47.3
