On Mon, May 03, 2021 at 10:58:33AM +1000, Nicholas Piggin wrote:
> Excerpts from Michal Suchánek's message of May 3, 2021 2:57 am:
> > On Tue, Apr 28, 2020 at 09:25:17PM +1000, Nicholas Piggin wrote:
> >> Provide an option to use ELFv2 ABI for big endian builds. This works on
> >> GCC and clang (since 2014). It is less well tested and supported by the
> >> GNU toolchain, but it can give some useful advantages of the ELFv2 ABI
> >> for BE (e.g., less stack usage). Some distros even build BE ELFv2
> >> userspace.
> >
> > Fixes BTFID failure on BE for me and the ELF ABIv2 kernel boots.
>
> What's the BTFID failure? Anything we can do to fix it on the v1 ABI or
> at least make it depend on BUILD_ELF_V2?
Looks like symbols are prefixed with a dot in ABIv1 and BTFID tool is
not aware of that. It can be disabled on ABIv1 easily.
Thanks
Michal
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 678c13967580..e703c26e9b80 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -305,6 +305,7 @@ config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
+ depends on !PPC64 || BUILD_ELF_V2
help
Generate deduplicated BTF type information from DWARF debug info.
Turning this on expects presence of pahole tool, which will convert
>
> >
> > Tested-by: Michal Suchánek <msucha...@suse.de>
> >
> > Also can we enable mprofile on BE now?
> >
> > I don't see anything endian-specific in the mprofile code at a glance
> > but don't have any idea how to test it.
>
> AFAIK it's just a different ABI for the _mcount call so just running
> some ftrace and ftrace with call graph should test it reasonably well.
>
> >
> > Thanks
> >
> > Michal
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 6a4ad11f6349..75b3afbfc378 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -495,7 +495,7 @@ config LD_HEAD_STUB_CATCH
> > If unsure, say "N".
> >
> > config MPROFILE_KERNEL
> > - depends on PPC64 && CPU_LITTLE_ENDIAN && FUNCTION_TRACER
> > + depends on PPC64 && BUILD_ELF_V2 && FUNCTION_TRACER
> > def_bool
> > $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC)
> > -I$(srctree)/include -D__KERNEL__)
>
> Good idea. I can't remember if I did a grep for LITTLE_ENDIAN to check
> for other such opportunities.
>
> Thanks,
> Nick
>
> >
> > config HOTPLUG_CPU
> >>
> >> Reviewed-by: Segher Boessenkool <seg...@kernel.crashing.org>
> >> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> >> ---
> >> Since v1:
> >> - Improved the override flavour name suggested by Segher.
> >> - Improved changelog wording.
> >>
> >>
> >> arch/powerpc/Kconfig | 19 +++++++++++++++++++
> >> arch/powerpc/Makefile | 15 ++++++++++-----
> >> arch/powerpc/boot/Makefile | 4 ++++
> >> drivers/crypto/vmx/Makefile | 8 ++++++--
> >> drivers/crypto/vmx/ppc-xlate.pl | 10 ++++++----
> >> 5 files changed, 45 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> >> index 924c541a9260..d9d2abc06c2c 100644
> >> --- a/arch/powerpc/Kconfig
> >> +++ b/arch/powerpc/Kconfig
> >> @@ -147,6 +147,7 @@ config PPC
> >> select ARCH_WEAK_RELEASE_ACQUIRE
> >> select BINFMT_ELF
> >> select BUILDTIME_TABLE_SORT
> >> + select BUILD_ELF_V2 if PPC64 && CPU_LITTLE_ENDIAN
> >> select CLONE_BACKWARDS
> >> select DCACHE_WORD_ACCESS if PPC64 && CPU_LITTLE_ENDIAN
> >> select DYNAMIC_FTRACE if FUNCTION_TRACER
> >> @@ -541,6 +542,24 @@ config KEXEC_FILE
> >> config ARCH_HAS_KEXEC_PURGATORY
> >> def_bool KEXEC_FILE
> >>
> >> +config BUILD_ELF_V2
> >> + bool
> >> +
> >> +config BUILD_BIG_ENDIAN_ELF_V2
> >> + bool "Build big-endian kernel using ELFv2 ABI (EXPERIMENTAL)"
> >> + depends on PPC64 && CPU_BIG_ENDIAN && EXPERT
> >> + default n
> >> + select BUILD_ELF_V2
> >> + help
> >> + This builds the kernel image using the ELFv2 ABI, which has a
> >> + reduced stack overhead and faster function calls. This does not
> >> + affect the userspace ABIs.
> >> +
> >> + ELFv2 is the standard ABI for little-endian, but for big-endian
> >> + this is an experimental option that is less tested (kernel and
> >> + toolchain). This requires gcc 4.9 or newer 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 f310c32e88a4..e306b39d847e 100644
> >> --- a/arch/powerpc/Makefile
> >> +++ b/arch/powerpc/Makefile
> >> @@ -92,10 +92,14 @@ 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_BUILD_ELF_V2
> >> +cflags-y += $(call cc-option,-mabi=elfv2,$(call
> >> cc-option,-mcall-aixdesc))
> >> +aflags-y += $(call cc-option,-mabi=elfv2)
> >> +else
> >> +cflags-y += $(call cc-option,-mabi=elfv1)
> >> +cflags-y += $(call cc-option,-mcall-aixdesc)
> >> +aflags-y += $(call cc-option,-mabi=elfv1)
> >> +endif
> >> endif
> >> endif
> >>
> >> @@ -144,7 +148,7 @@ endif
> >>
> >> CFLAGS-$(CONFIG_PPC64) := $(call cc-option,-mtraceback=no)
> >> ifndef CONFIG_CC_IS_CLANG
> >> -ifdef CONFIG_CPU_LITTLE_ENDIAN
> >> +ifdef CONFIG_BUILD_ELF_V2
> >> CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2,$(call
> >> cc-option,-mcall-aixdesc))
> >> AFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2)
> >> else
> >> @@ -153,6 +157,7 @@ CFLAGS-$(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 c53a1b8bba8b..03942d08695d 100644
> >> --- a/arch/powerpc/boot/Makefile
> >> +++ b/arch/powerpc/boot/Makefile
> >> @@ -41,6 +41,10 @@ endif
> >>
> >> BOOTCFLAGS += -isystem $(shell $(BOOTCC) -print-file-name=include)
> >>
> >> +ifdef CONFIG_BUILD_ELF_V2
> >> +BOOTCFLAGS += $(call cc-option,-mabi=elfv2)
> >> +endif
> >> +
> >> ifdef CONFIG_CPU_BIG_ENDIAN
> >> BOOTCFLAGS += -mbig-endian
> >> else
> >> diff --git a/drivers/crypto/vmx/Makefile b/drivers/crypto/vmx/Makefile
> >> index 709670d2b553..9aea34602beb 100644
> >> --- a/drivers/crypto/vmx/Makefile
> >> +++ b/drivers/crypto/vmx/Makefile
> >> @@ -5,18 +5,22 @@ vmx-crypto-objs := vmx.o aesp8-ppc.o ghashp8-ppc.o aes.o
> >> aes_cbc.o aes_ctr.o aes
> >> ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y)
> >> override flavour := linux-ppc64le
> >> else
> >> +ifdef CONFIG_BUILD_ELF_V2
> >> +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
> >> $(call if_changed,perl)
> >>
> >> clean-files := aesp8-ppc.S ghashp8-ppc.S
> >> diff --git a/drivers/crypto/vmx/ppc-xlate.pl
> >> b/drivers/crypto/vmx/ppc-xlate.pl
> >> index 36db2ef09e5b..9db0937d318b 100644
> >> --- a/drivers/crypto/vmx/ppc-xlate.pl
> >> +++ b/drivers/crypto/vmx/ppc-xlate.pl
> >> @@ -9,6 +9,8 @@ open STDOUT,">$output" || die "can't open $output: $!";
> >>
> >> my %GLOBALS;
> >> my $dotinlocallabels=($flavour=~/linux/)?1:0;
> >> +my $abielfv2=(($flavour =~ /linux-ppc64le/) or ($flavour =~
> >> /linux-ppc64-elfv2/))?1:0;
> >> +my $dotfunctions=($abielfv2=~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 ($abielfv2);
> >> $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 $no_vrsave = ($abielfv2);
> >> my $mtspr = sub {
> >> my ($f,$idx,$ra) = @_;
> >> if ($idx == 256 && $no_vrsave) {
> >> --
> >> 2.23.0
> >>
> >
