[PATCH v5 5/6] Makefile: Support building with Clang and LLVM binutils
Bin Meng
bmeng.cn at gmail.com
Sun Jul 11 08:03:15 PDT 2021
On Sun, Jul 11, 2021 at 10:46 PM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
>
> On 11 Jul 2021, at 15:26, Bin Meng <bmeng.cn at gmail.com> wrote:
> >
> > On Sun, Jul 11, 2021 at 10:29 AM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
> >>
> >> This is intended to mirror the Linux kernel. Building with CC=clang will
> >> use Clang as the compiler but default to using the existing binutils.
> >> Building with LLVM=1 will default to using Clang and LLVM binutils.
> >>
> >> Whilst GCC will accept the -N linker option and forward it on to the
> >> linker, Clang will not, and so in order to support both compilers we
> >> must use -Wl, to forward it to the linker as is required for most other
> >> linker options.
> >>
> >> Note that there is currently a bug when using Clang as the compiler and
> >> riscv64-linux-gnu-ld as the linker for FW_PIC=y. At first glance this
> >> appears to be a bug in GNU binutils, but this could also be Clang or
> >> OpenSBI at fault in some subtle way. Thus, for now, advise that this
> >> combination be avoided.
> >>
> >> Signed-off-by: Jessica Clarke <jrtc27 at jrtc27.com>
> >> ---
> >> Makefile | 66 +++++++++++++++++++++++++++++++++++++++++++++++++------
> >> README.md | 48 ++++++++++++++++++++++++++++++++++++++--
> >> 2 files changed, 105 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/Makefile b/Makefile
> >> index ba06313..5c188d5 100644
> >> --- a/Makefile
> >> +++ b/Makefile
> >> @@ -76,26 +76,54 @@ OPENSBI_VERSION_MINOR=`grep "define OPENSBI_VERSION_MINOR" $(include_dir)/sbi/sb
> >> OPENSBI_VERSION_GIT=$(shell if [ -d $(src_dir)/.git ]; then git describe 2> /dev/null; fi)
> >>
> >> # Setup compilation commands
> >> +ifneq ($(LLVM),)
> >> +CC = clang
> >> +AR = llvm-ar
> >> +LD = ld.lld
> >> +OBJCOPY = llvm-objcopy
> >> +else
> >> ifdef CROSS_COMPILE
> >> CC = $(CROSS_COMPILE)gcc
> >> -CPP = $(CROSS_COMPILE)cpp
> >> AR = $(CROSS_COMPILE)ar
> >> LD = $(CROSS_COMPILE)ld
> >> OBJCOPY = $(CROSS_COMPILE)objcopy
> >> else
> >> CC ?= gcc
> >> -CPP ?= cpp
> >> AR ?= ar
> >> LD ?= ld
> >> OBJCOPY ?= objcopy
> >> endif
> >> +endif
> >> +CPP = $(CC) -E
> >> AS = $(CC)
> >> DTC = dtc
> >>
> >> -# Guess the compillers xlen
> >> -OPENSBI_CC_XLEN := $(shell TMP=`$(CC) -dumpmachine | sed 's/riscv\([0-9][0-9]\).*/\1/'`; echo $${TMP})
> >> +ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
> >> +CC_IS_CLANG = y
> >> +else
> >> +CC_IS_CLANG = n
> >> +endif
> >> +
> >> +ifneq ($(shell $(LD) --version 2>&1 | head -n 1 | grep LLD),)
> >> +LD_IS_LLD = y
> >> +else
> >> +LD_IS_LLD = n
> >> +endif
> >> +
> >> +ifeq ($(CC_IS_CLANG),y)
> >> +ifneq ($(CROSS_COMPILE),)
> >> +CLANG_TARGET = --target=$(notdir $(CROSS_COMPILE:%-=%))
> >> +endif
> >> +endif
> >> +
> >> +# Guess the compiler's XLEN
> >> +OPENSBI_CC_XLEN := $(shell TMP=`$(CC) $(CLANG_TARGET) -dumpmachine | sed 's/riscv\([0-9][0-9]\).*/\1/'`; echo $${TMP})
> >> +
> >> +# Guess the compiler's ABI and ISA
> >> +ifneq ($(CC_IS_CLANG),y)
> >> OPENSBI_CC_ABI := $(shell TMP=`$(CC) -v 2>&1 | sed -n 's/.*\(with\-abi=\([a-zA-Z0-9]*\)\).*/\2/p'`; echo $${TMP})
> >> OPENSBI_CC_ISA := $(shell TMP=`$(CC) -v 2>&1 | sed -n 's/.*\(with\-arch=\([a-zA-Z0-9]*\)\).*/\2/p'`; echo $${TMP})
> >> +endif
> >>
> >> # Setup platform XLEN
> >> ifndef PLATFORM_RISCV_XLEN
> >> @@ -106,8 +134,21 @@ ifndef PLATFORM_RISCV_XLEN
> >> endif
> >> endif
> >>
> >> +ifeq ($(CC_IS_CLANG),y)
> >> +ifeq ($(CROSS_COMPILE),)
> >> +CLANG_TARGET = --target=riscv$(PLATFORM_RISCV_XLEN)-unknown-elf
> >> +endif
> >> +endif
> >> +
> >> +ifeq ($(LD_IS_LLD),y)
> >> +RELAX_FLAG = -mno-relax
> >> +USE_LD_FLAG = -fuse-ld=lld
> >> +else
> >> +USE_LD_FLAG = -fuse-ld=bfd
> >> +endif
> >> +
> >> # Check whether the linker supports creating PIEs
> >> -OPENSBI_LD_PIE := $(shell $(CC) -fPIE -nostdlib -Wl,-pie -x c /dev/null -o /dev/null >/dev/null 2>&1 && echo y || echo n)
> >> +OPENSBI_LD_PIE := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) $(USE_LD_FLAG) -fPIE -nostdlib -Wl,-pie -x c /dev/null -o /dev/null >/dev/null 2>&1 && echo y || echo n)
> >
> > It looks like this combination does not work? Both
> > riscv64-unknown-elf-gcc and LLVM are in my $PATH, but ld.lld cannot be
> > located.
> >
> > $ riscv64-unknown-elf-gcc -fPIE -fuse-ld=lld -nostdlib -Wl,-pie -x c
> > /dev/null -o /dev/null 2>&1
> > collect2: fatal error: cannot find 'ld'
> > compilation terminated.
> >
> > So this will result in a PDE image, even though LLD supports PIE.
>
> Isn’t this the same issue as you reported elsewhere, and will
> ultimately result in the same error, this time not suppressed, at link
> time too?
Yeah, the same issue I reported in the cover letter. Sorry :)
So I followed your advice in that thread, that I created a symbolic
link in my cross-compile GCC toolchain bin directory,
riscv64-unknown-elf-ld.lld to point to the actual LLVM ld.lld. Then
this 'collect2' error is gone. I suggest we can document this in the
doc for the mixed usage (GCC to compile + LLD to link).
But still the build failed in the end:
$ make CC=riscv64-unknown-elf-gcc LLVM=1 PLATFORM=generic V=1
mkdir -p `dirname
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test_head.o`;
echo " AS platform/generic/firmware/payloads/test_head.o";
riscv64-unknown-elf-gcc -g -Wall -nostdlib -fno-omit-frame-pointer
-fno-optimize-sibling-calls -mno-save-restore -mstrict-align
-mabi=lp64 -march=rv64imafdc -mcmodel=medany -mno-relax
-I/home/test/git/opensbi/platform/generic/include
-I/home/test/git/opensbi/include
-DOPENSBI_VERSION_GIT="\"v0.9-111-g401461d\""
-I/home/test/git/opensbi/lib/utils/libfdt/ -DFW_PIC
-DFW_TEXT_START=0x80000000 -DFW_JUMP_ADDR=0x80200000
-DFW_JUMP_FDT_ADDR=0x82200000
-DFW_PAYLOAD_PATH=\"/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.bin\"
-DFW_PAYLOAD_OFFSET=0x200000 -DFW_PAYLOAD_FDT_ADDR=0x82200000 -fpic
-I/home/test/git/opensbi/firmware/payloads -D__OBJNAME__=test_head -c
/home/test/git/opensbi/firmware/payloads/test_head.S -o
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test_head.o
AS platform/generic/firmware/payloads/test_head.o
mkdir -p `dirname
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test_main.o`;
echo " CC platform/generic/firmware/payloads/test_main.o";
riscv64-unknown-elf-gcc -g -Wall -Werror -ffreestanding -nostdlib
-fno-stack-protector -fno-strict-aliasing -O2 -fno-omit-frame-pointer
-fno-optimize-sibling-calls -mno-save-restore -mstrict-align
-mabi=lp64 -march=rv64imafdc -mcmodel=medany -mno-relax
-I/home/test/git/opensbi/platform/generic/include
-I/home/test/git/opensbi/include
-DOPENSBI_VERSION_GIT="\"v0.9-111-g401461d\""
-I/home/test/git/opensbi/lib/utils/libfdt/ -DFW_PIC
-DFW_TEXT_START=0x80000000 -DFW_JUMP_ADDR=0x80200000
-DFW_JUMP_FDT_ADDR=0x82200000
-DFW_PAYLOAD_PATH=\"/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.bin\"
-DFW_PAYLOAD_OFFSET=0x200000 -DFW_PAYLOAD_FDT_ADDR=0x82200000
-fno-pie -no-pie -fPIE -pie
-I/home/test/git/opensbi/firmware/payloads -D__OBJNAME__=test_main -c
/home/test/git/opensbi/firmware/payloads/test_main.c -o
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test_main.o
CC platform/generic/firmware/payloads/test_main.o
mkdir -p `dirname
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.o`;
echo " MERGE platform/generic/firmware/payloads/test.o"; ld.lld -r
-b elf -m elf64lriscv
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test_head.o
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test_main.o
-o /home/test/git/opensbi/build/platform/generic/firmware/payloads/test.o
MERGE platform/generic/firmware/payloads/test.o
mkdir -p `dirname
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.elf`;
echo " ELF platform/generic/firmware/payloads/test.elf";
riscv64-unknown-elf-gcc -g -Wall -Werror -ffreestanding -nostdlib
-fno-stack-protector -fno-strict-aliasing -O2 -fno-omit-frame-pointer
-fno-optimize-sibling-calls -mno-save-restore -mstrict-align
-mabi=lp64 -march=rv64imafdc -mcmodel=medany -mno-relax
-I/home/test/git/opensbi/platform/generic/include
-I/home/test/git/opensbi/include
-DOPENSBI_VERSION_GIT="\"v0.9-111-g401461d\""
-I/home/test/git/opensbi/lib/utils/libfdt/ -DFW_PIC
-DFW_TEXT_START=0x80000000 -DFW_JUMP_ADDR=0x80200000
-DFW_JUMP_FDT_ADDR=0x82200000
-DFW_PAYLOAD_PATH=\"/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.bin\"
-DFW_PAYLOAD_OFFSET=0x200000 -DFW_PAYLOAD_FDT_ADDR=0x82200000
-fno-pie -no-pie -fPIE -pie
/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.o
/home/test/git/opensbi/build/platform/generic/lib/libplatsbi.a
-fuse-ld=lld -Wl,--build-id=none -Wl,-N -Wl,--no-dynamic-linker
-Wl,-pie -Wl,-T/home/test/git/opensbi/build/platform/generic/firmware/payloads/test.elf.ld
-o /home/test/git/opensbi/build/platform/generic/firmware/payloads/test.elf
ELF platform/generic/firmware/payloads/test.elf
riscv64-unknown-elf-ld.lld: error: test_main.c:(.entry+0x0):
relocation R_RISCV_ALIGN requires unimplemented linker relaxation;
recompile with -mno-relax
riscv64-unknown-elf-ld.lld: error:
/home/test/git/opensbi/firmware/payloads/test_head.S:38:(.entry+0x84):
relocation R_RISCV_ALIGN requires unimplemented linker relaxation;
recompile with -mno-relax
riscv64-unknown-elf-ld.lld: error:
/home/test/git/opensbi/firmware/payloads/test_head.S:39:(.entry+0x90):
relocation R_RISCV_ALIGN requires unimplemented linker relaxation;
recompile with -mno-relax
collect2: error: ld returned 1 exit status
So far the only fully working one is the complete LLVM build. The
other 2 mixed usages are broken. It seems the toolchains guys created
some sort of flexibility but opened lots of possibilities to break :)
> Using GCC as a driver for LLD has always been a painful
> combination, in part because historically there’s been very little
> interest in supporting it from the GNU side; it wasn’t until a few
> years ago (I think late 2018 or early 2019?) that -fuse-ld=lld was even
> accepted as an option, and that was just a minimal patch that reused
> all the logic for BFD and gold despite the fact that that’s
> unnecessarily restrictive for LLD and doesn’t support cases like this
> properly.
Regards,
Bin
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