On Fri, Jun 11, 2021 at 07:39:59PM +1000, Nicholas Piggin wrote: > Provide an option to build big-endian kernels using the ELFv2 ABI. This > works on GCC only so far, although it is rumored to work with clang > that's not been tested yet. A new module version check ensures the > module ELF ABI level matches the kernel build. > > This can give big-endian kernels some useful advantages of the ELFv2 ABI > (e.g., less stack usage, -mprofile-kernel, 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 <msucha...@suse.de> > Reviewed-by: Segher Boessenkool <seg...@kernel.crashing.org> > Signed-off-by: Nicholas Piggin <npig...@gmail.com> > --- > arch/powerpc/Kconfig | 22 ++++++++++++++++++++++ > arch/powerpc/Makefile | 18 ++++++++++++------ > arch/powerpc/boot/Makefile | 4 +++- > arch/powerpc/include/asm/module.h | 24 ++++++++++++++++++++++++ > arch/powerpc/kernel/vdso64/Makefile | 13 +++++++++++++ > drivers/crypto/vmx/Makefile | 8 ++++++-- > drivers/crypto/vmx/ppc-xlate.pl | 10 ++++++---- > 7 files changed, 86 insertions(+), 13 deletions(-) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 088dd2afcfe4..093f973a28b9 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -163,6 +163,7 @@ config PPC > select ARCH_WEAK_RELEASE_ACQUIRE > select BINFMT_ELF > select BUILDTIME_TABLE_SORT > + select PPC64_BUILD_ELF_V2_ABI if PPC64 && CPU_LITTLE_ENDIAN > select CLONE_BACKWARDS > select DCACHE_WORD_ACCESS if PPC64 && CPU_LITTLE_ENDIAN > select DMA_OPS_BYPASS if PPC64 > @@ -561,6 +562,27 @@ config KEXEC_FILE > config ARCH_HAS_KEXEC_PURGATORY > def_bool KEXEC_FILE > > +config PPC64_BUILD_ELF_V2_ABI > + bool > + > +config PPC64_BUILD_BIG_ENDIAN_ELF_V2_ABI > + bool "Build big-endian kernel using ELF ABI V2 (EXPERIMENTAL)" > + depends on PPC64 && CPU_BIG_ENDIAN && EXPERT > + depends on CC_IS_GCC && LD_VERSION >= 22400 > + default n > + select PPC64_BUILD_ELF_V2_ABI > + 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 || FSL_BOOKE)) > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile > index 3212d076ac6a..b90b5cb799aa 100644 > --- a/arch/powerpc/Makefile > +++ b/arch/powerpc/Makefile > @@ -91,10 +91,14 @@ endif > > ifdef CONFIG_PPC64 > ifndef CONFIG_CC_IS_CLANG > -cflags-$(CONFIG_CPU_BIG_ENDIAN) += $(call cc-option,-mabi=elfv1) > -cflags-$(CONFIG_CPU_BIG_ENDIAN) += $(call > cc-option,-mcall-aixdesc) > -aflags-$(CONFIG_CPU_BIG_ENDIAN) += $(call cc-option,-mabi=elfv1) > -aflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -mabi=elfv2 > +ifdef CONFIG_PPC64_BUILD_ELF_V2_ABI > +cflags-y += $(call cc-option,-mabi=elfv2) > +aflags-y += $(call cc-option,-mabi=elfv2) > +else > +cflags-y += $(call cc-option,-mabi=elfv1) > +cflags-y += $(call cc-option,-mcall-aixdesc) > +aflags-y += $(call cc-option,-mabi=elfv1) > +endif > endif > endif > > @@ -142,15 +146,17 @@ endif > > CFLAGS-$(CONFIG_PPC64) := $(call cc-option,-mtraceback=no) > ifndef CONFIG_CC_IS_CLANG > -ifdef CONFIG_CPU_LITTLE_ENDIAN > -CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2,$(call > cc-option,-mcall-aixdesc)) > +ifdef CONFIG_PPC64_BUILD_ELF_V2_ABI > +CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2) > AFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2) > else > +# Keep these in synch with arch/powerpc/kernel/vdso64/Makefile > CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv1) > CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mcall-aixdesc) > AFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv1) > endif > endif > + > CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mcmodel=medium,$(call > cc-option,-mminimal-toc)) > CFLAGS-$(CONFIG_PPC64) += $(call > cc-option,-mno-pointers-to-nested-functions) > > diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile > index 2b8da923ceca..be84a72f8258 100644 > --- a/arch/powerpc/boot/Makefile > +++ b/arch/powerpc/boot/Makefile > @@ -40,6 +40,9 @@ BOOTCFLAGS := -Wall -Wundef -Wstrict-prototypes > -Wno-trigraphs \ > > ifdef CONFIG_PPC64_BOOT_WRAPPER > BOOTCFLAGS += -m64 > +ifdef CONFIG_PPC64_BUILD_ELF_V2_ABI > +BOOTCFLAGS += $(call cc-option,-mabi=elfv2) > +endif > else > BOOTCFLAGS += -m32 > endif > @@ -50,7 +53,6 @@ ifdef CONFIG_CPU_BIG_ENDIAN > BOOTCFLAGS += -mbig-endian > else > BOOTCFLAGS += -mlittle-endian > -BOOTCFLAGS += $(call cc-option,-mabi=elfv2) > endif > > BOOTAFLAGS := -D__ASSEMBLY__ $(BOOTCFLAGS) -nostdinc > diff --git a/arch/powerpc/include/asm/module.h > b/arch/powerpc/include/asm/module.h > index 857d9ff24295..043e11068ff4 100644 > --- a/arch/powerpc/include/asm/module.h > +++ b/arch/powerpc/include/asm/module.h > @@ -52,6 +52,30 @@ struct mod_arch_specific { > unsigned int num_bugs; > }; > > +/* > + * Check kernel module ELF header architecture specific compatibility. > + */ > +static inline bool elf_check_module_arch(Elf_Ehdr *hdr) > +{ > + if (!elf_check_arch(hdr)) > + return false; > + > + if (IS_ENABLED(CONFIG_PPC64)) { > + unsigned long abi_level = hdr->e_flags & 0x3; > + > + if (IS_ENABLED(CONFIG_PPC64_BUILD_ELF_V2_ABI)) { > + if (abi_level != 2) > + return false; > + } else { > + if (abi_level >= 2) > + return false; > + } > + } > + > + return true; > +} > +#define elf_check_module_arch elf_check_module_arch > + > /* > * Select ELF headers. > * Make empty section for module_frob_arch_sections to expand. Shouldn't this part go to the second patch?
Thanks Michal > diff --git a/arch/powerpc/kernel/vdso64/Makefile > b/arch/powerpc/kernel/vdso64/Makefile > index 2813e3f98db6..d783c07e558f 100644 > --- a/arch/powerpc/kernel/vdso64/Makefile > +++ b/arch/powerpc/kernel/vdso64/Makefile > @@ -25,6 +25,19 @@ KCOV_INSTRUMENT := n > UBSAN_SANITIZE := n > KASAN_SANITIZE := n > > +# Always build vdso64 with ELFv1 ABI for BE kernels > +ifdef CONFIG_PPC64_BUILD_ELF_V2_ABI > +ifdef CONFIG_CPU_BIG_ENDIAN > +KBUILD_CFLAGS := $(filter-out -mabi=elfv2,$(KBUILD_CFLAGS)) > +KBUILD_AFLAGS := $(filter-out -mabi=elfv2,$(KBUILD_AFLAGS)) > + > +# These are derived from arch/powerpc/Makefile > +KBUILD_CFLAGS += $(call cc-option,-mabi=elfv1) > +KBUILD_CFLAGS += $(call cc-option,-mcall-aixdesc) > +KBUILD_AFLAGS += $(call cc-option,-mabi=elfv1) > +endif > +endif > + > ccflags-y := -shared -fno-common -fno-builtin -nostdlib \ > -Wl,-soname=linux-vdso64.so.1 -Wl,--hash-style=both > asflags-y := -D__VDSO64__ -s > diff --git a/drivers/crypto/vmx/Makefile b/drivers/crypto/vmx/Makefile > index 709670d2b553..d9ccf9fc3483 100644 > --- a/drivers/crypto/vmx/Makefile > +++ b/drivers/crypto/vmx/Makefile > @@ -5,18 +5,22 @@ vmx-crypto-objs := vmx.o aesp8-ppc.o ghashp8-ppc.o aes.o > aes_cbc.o aes_ctr.o aes > ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y) > override flavour := linux-ppc64le > else > +ifdef CONFIG_PPC64_BUILD_ELF_V2_ABI > +override flavour := linux-ppc64-elfv2 > +else > override flavour := linux-ppc64 > endif > +endif > > quiet_cmd_perl = PERL $@ > cmd_perl = $(PERL) $(<) $(flavour) > $(@) > > targets += aesp8-ppc.S ghashp8-ppc.S > > -$(obj)/aesp8-ppc.S: $(src)/aesp8-ppc.pl FORCE > +$(obj)/aesp8-ppc.S: $(src)/aesp8-ppc.pl $(src)/ppc-xlate.pl FORCE > $(call if_changed,perl) > > -$(obj)/ghashp8-ppc.S: $(src)/ghashp8-ppc.pl FORCE > +$(obj)/ghashp8-ppc.S: $(src)/ghashp8-ppc.pl $(src)/ppc-xlate.pl FORCE > $(call if_changed,perl) > > clean-files := aesp8-ppc.S ghashp8-ppc.S > diff --git a/drivers/crypto/vmx/ppc-xlate.pl b/drivers/crypto/vmx/ppc-xlate.pl > index 36db2ef09e5b..b583898c11ae 100644 > --- a/drivers/crypto/vmx/ppc-xlate.pl > +++ b/drivers/crypto/vmx/ppc-xlate.pl > @@ -9,6 +9,8 @@ open STDOUT,">$output" || die "can't open $output: $!"; > > my %GLOBALS; > my $dotinlocallabels=($flavour=~/linux/)?1:0; > +my $elfv2abi=(($flavour =~ /linux-ppc64le/) or ($flavour =~ > /linux-ppc64-elfv2/))?1:0; > +my $dotfunctions=($elfv2abi=~1)?0:1; > > ################################################################ > # directives which need special treatment on different platforms > @@ -40,7 +42,7 @@ my $globl = sub { > }; > my $text = sub { > my $ret = ($flavour =~ /aix/) ? ".csect\t.text[PR],7" : ".text"; > - $ret = ".abiversion 2\n".$ret if ($flavour =~ /linux.*64le/); > + $ret = ".abiversion 2\n".$ret if ($elfv2abi); > $ret; > }; > my $machine = sub { > @@ -56,8 +58,8 @@ my $size = sub { > if ($flavour =~ /linux/) > { shift; > my $name = shift; $name =~ s|^[\.\_]||; > - my $ret = ".size $name,.-".($flavour=~/64$/?".":"").$name; > - $ret .= "\n.size .$name,.-.$name" if ($flavour=~/64$/); > + my $ret = ".size $name,.-".($dotfunctions?".":"").$name; > + $ret .= "\n.size .$name,.-.$name" if ($dotfunctions); > $ret; > } > else > @@ -142,7 +144,7 @@ my $vmr = sub { > > # Some ABIs specify vrsave, special-purpose register #256, as reserved > # for system use. > -my $no_vrsave = ($flavour =~ /linux-ppc64le/); > +my $no_vrsave = ($elfv2abi); > my $mtspr = sub { > my ($f,$idx,$ra) = @_; > if ($idx == 256 && $no_vrsave) { > -- > 2.23.0 >