diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2022-11-28 14:15:39 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2022-12-02 17:54:07 +1100 |
| commit | 5017b45946722bdd20ac255c9ae7273b78d1f12e (patch) | |
| tree | dc757f1286ffb73a54354b3ca5007edcc5c48285 | |
| parent | 505ea33089dcfc3ee3201b0fcb94751165805413 (diff) | |
powerpc/64: Option to build big-endian with ELFv2 ABI
Provide an option to build big-endian kernels using the ELFv2 ABI. This
works on GCC only for now. Clang is rumored to support this, but core
build files need updating first, at least.
This gives big-endian kernels useful advantages of the ELFv2 ABI, e.g.,
less stack usage, -mprofile-kernel support, better compatibility with
eBPF tools.
BE+ELFv2 is not officially supported by the GNU toolchain, but it works
fine in testing and has been used by some userspace for some time (e.g.,
Void Linux).
Tested-by: Michal Suchánek <msuchanek@suse.de>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221128041539.1742489-5-npiggin@gmail.com
| -rw-r--r-- | arch/powerpc/Kconfig | 21 | ||||
| -rw-r--r-- | arch/powerpc/platforms/Kconfig.cputype | 4 |
2 files changed, 23 insertions, 2 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index abaf1ef1795c..1a134c9769f8 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -1,6 +1,9 @@ # SPDX-License-Identifier: GPL-2.0 source "arch/powerpc/platforms/Kconfig.cputype" +config CC_HAS_ELFV2 + def_bool PPC64 && $(cc-option, -mabi=elfv2) + config 32BIT bool default y if PPC32 @@ -586,6 +589,24 @@ config KEXEC_FILE config ARCH_HAS_KEXEC_PURGATORY def_bool KEXEC_FILE +config PPC64_BIG_ENDIAN_ELF_ABI_V2 + bool "Build big-endian kernel using ELF ABI V2 (EXPERIMENTAL)" + depends on PPC64 && CPU_BIG_ENDIAN + depends on CC_HAS_ELFV2 + depends on LD_IS_BFD && LD_VERSION >= 22400 + default n + help + This builds the kernel image using the "Power Architecture 64-Bit ELF + V2 ABI Specification", which has a reduced stack overhead and faster + function calls. This internal kernel ABI option does not affect + userspace compatibility. + + The V2 ABI is standard for 64-bit little-endian, but for big-endian + it is less well tested by kernel and toolchain. However some distros + build userspace this way, and it can produce a functioning kernel. + + This requires GCC and binutils 2.24 or newer. + config RELOCATABLE bool "Build a relocatable kernel" depends on PPC64 || (FLATMEM && (44x || PPC_85xx)) diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype index 7bac213b4125..9563336e3348 100644 --- a/arch/powerpc/platforms/Kconfig.cputype +++ b/arch/powerpc/platforms/Kconfig.cputype @@ -580,10 +580,10 @@ config CPU_LITTLE_ENDIAN endchoice config PPC64_ELF_ABI_V1 - def_bool PPC64 && CPU_BIG_ENDIAN + def_bool PPC64 && (CPU_BIG_ENDIAN && !PPC64_BIG_ENDIAN_ELF_ABI_V2) config PPC64_ELF_ABI_V2 - def_bool PPC64 && CPU_LITTLE_ENDIAN + def_bool PPC64 && !PPC64_ELF_ABI_V1 config PPC64_BOOT_WRAPPER def_bool n |