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[60.242.147.73]) by smtp.gmail.com with ESMTPSA id o139sm4981655pfd.96.2021.06.11.02.40.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Jun 2021 02:40:12 -0700 (PDT) From: Nicholas Piggin To: linuxppc-dev@lists.ozlabs.org Cc: Nicholas Piggin , linux-kernel@vger.kernel.org, Jessica Yu , =?UTF-8?q?Michal=20Such=C3=A1nek?= , Segher Boessenkool Subject: [PATCH v4 2/2] powerpc/64: Option to use ELF V2 ABI for big-endian kernels Date: Fri, 11 Jun 2021 19:39:59 +1000 Message-Id: <20210611093959.821525-3-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210611093959.821525-1-npiggin@gmail.com> References: <20210611093959.821525-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Reviewed-by: Segher Boessenkool Signed-off-by: Nicholas Piggin --- 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. 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