| Message ID | 20201003021904.1468678-1-yhs@fb.com |
|---|---|
| State | New |
| Headers | show |
| Series | [bpf-next,1/2] samples/bpf: change Makefile to cope with latest llvm | expand |
On Fri, Oct 2, 2020 at 7:19 PM Yonghong Song <yhs@fb.com> wrote: > > With latest llvm trunk, bpf programs under samples/bpf > directory, if using CORE, may experience the following > errors: > > LLVM ERROR: Cannot select: intrinsic %llvm.preserve.struct.access.index > PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace. > Stack dump: > 0. Program arguments: llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o > 1. Running pass 'Function Pass Manager' on module '<stdin>'. > 2. Running pass 'BPF DAG->DAG Pattern Instruction Selection' on function '@bpf_prog1' > #0 0x000000000183c26c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) > (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x183c26c) > ... > #7 0x00000000017c375e (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x17c375e) > #8 0x00000000016a75c5 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) > (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16a75c5) > #9 0x00000000016ab4f8 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, > unsigned int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16ab4f8) > ... > Aborted (core dumped) | llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o > > The reason is due to llvm change https://reviews.llvm.org/D87153 > where the CORE relocation global generation is moved from the beginning > of target dependent optimization (llc) to the beginning > of target independent optimization (opt). > > Since samples/bpf programs did not use vmlinux.h and its clang compilation > uses native architecture, we need to adjust arch triple at opt level > to do CORE relocation global generation properly. Otherwise, the above > error will appear. > > This patch fixed the issue by introduce opt and llvm-dis to compilation chain, > which will do proper CORE relocation global generation as well as O2 level > optimization. Tested with llvm10, llvm11 and trunk/llvm12. > > Signed-off-by: Yonghong Song <yhs@fb.com> > --- > samples/bpf/Makefile | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > index 4f1ed0e3cf9f..79c5fdea63d2 100644 > --- a/samples/bpf/Makefile > +++ b/samples/bpf/Makefile > @@ -211,6 +211,8 @@ TPROGLDLIBS_xsk_fwd += -pthread > # make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang > LLC ?= llc > CLANG ?= clang > +OPT ?= opt > +LLVM_DIS ?= llvm-dis > LLVM_OBJCOPY ?= llvm-objcopy > BTF_PAHOLE ?= pahole > > @@ -314,7 +316,9 @@ $(obj)/%.o: $(src)/%.c > -Wno-address-of-packed-member -Wno-tautological-compare \ > -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ > -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ > - -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ > + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ > + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ > + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ I keep forgetting exact details of why we do this native clang + llc pipeline instead of just doing `clang -target bpf`? Is it still relevant and necessary, or we can just simplify it now? > ifeq ($(DWARF2BTF),y) > $(BTF_PAHOLE) -J $@ > endif > -- > 2.24.1 >
On 10/2/20 9:22 PM, Andrii Nakryiko wrote: > On Fri, Oct 2, 2020 at 7:19 PM Yonghong Song <yhs@fb.com> wrote: >> >> With latest llvm trunk, bpf programs under samples/bpf >> directory, if using CORE, may experience the following >> errors: >> >> LLVM ERROR: Cannot select: intrinsic %llvm.preserve.struct.access.index >> PLEASE submit a bug report to https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=_D9tvuWQ6EbYqcMBdVB0qqRMVdV6Etws5ITtx8Pa1ZM&s=BwTAvhipPl-Az_WaiJDbqU8yl__NvG8W4HmCqWqHdqg&e= and include the crash backtrace. >> Stack dump: >> 0. Program arguments: llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o >> 1. Running pass 'Function Pass Manager' on module '<stdin>'. >> 2. Running pass 'BPF DAG->DAG Pattern Instruction Selection' on function '@bpf_prog1' >> #0 0x000000000183c26c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) >> (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x183c26c) >> ... >> #7 0x00000000017c375e (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x17c375e) >> #8 0x00000000016a75c5 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) >> (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16a75c5) >> #9 0x00000000016ab4f8 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, >> unsigned int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16ab4f8) >> ... >> Aborted (core dumped) | llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o >> >> The reason is due to llvm change https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D87153&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=_D9tvuWQ6EbYqcMBdVB0qqRMVdV6Etws5ITtx8Pa1ZM&s=fo_LvXqHJx_m0m0pJJiDdOUcOzVXm2_iYoxPhpqpzng&e= >> where the CORE relocation global generation is moved from the beginning >> of target dependent optimization (llc) to the beginning >> of target independent optimization (opt). >> >> Since samples/bpf programs did not use vmlinux.h and its clang compilation >> uses native architecture, we need to adjust arch triple at opt level >> to do CORE relocation global generation properly. Otherwise, the above >> error will appear. >> >> This patch fixed the issue by introduce opt and llvm-dis to compilation chain, >> which will do proper CORE relocation global generation as well as O2 level >> optimization. Tested with llvm10, llvm11 and trunk/llvm12. >> >> Signed-off-by: Yonghong Song <yhs@fb.com> >> --- >> samples/bpf/Makefile | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile >> index 4f1ed0e3cf9f..79c5fdea63d2 100644 >> --- a/samples/bpf/Makefile >> +++ b/samples/bpf/Makefile >> @@ -211,6 +211,8 @@ TPROGLDLIBS_xsk_fwd += -pthread >> # make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang >> LLC ?= llc >> CLANG ?= clang >> +OPT ?= opt >> +LLVM_DIS ?= llvm-dis >> LLVM_OBJCOPY ?= llvm-objcopy >> BTF_PAHOLE ?= pahole >> >> @@ -314,7 +316,9 @@ $(obj)/%.o: $(src)/%.c >> -Wno-address-of-packed-member -Wno-tautological-compare \ >> -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ >> -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ >> - -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ >> + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ >> + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ >> + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ > > I keep forgetting exact details of why we do this native clang + llc > pipeline instead of just doing `clang -target bpf`? Is it still samples/bpf programs did not use vmlinux.h. they directly use kernel-devel headers, hence they need to first compile with native arch for clang but later change target arch to bpf to generate final byte code. They cannot just do 'clang -target bpf' without vmlinux.h. But changing to use vmlinux.h is a much bigger project and I merely want to make it just work so people won't make/compile samples/bpf and get compilation errors. > relevant and necessary, or we can just simplify it now? > >> ifeq ($(DWARF2BTF),y) >> $(BTF_PAHOLE) -J $@ >> endif >> -- >> 2.24.1 >>
On Fri, Oct 2, 2020 at 10:16 PM Yonghong Song <yhs@fb.com> wrote: > > > > On 10/2/20 9:22 PM, Andrii Nakryiko wrote: > > On Fri, Oct 2, 2020 at 7:19 PM Yonghong Song <yhs@fb.com> wrote: > >> > >> With latest llvm trunk, bpf programs under samples/bpf > >> directory, if using CORE, may experience the following > >> errors: > >> > >> LLVM ERROR: Cannot select: intrinsic %llvm.preserve.struct.access.index > >> PLEASE submit a bug report to https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=_D9tvuWQ6EbYqcMBdVB0qqRMVdV6Etws5ITtx8Pa1ZM&s=BwTAvhipPl-Az_WaiJDbqU8yl__NvG8W4HmCqWqHdqg&e= and include the crash backtrace. > >> Stack dump: > >> 0. Program arguments: llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o > >> 1. Running pass 'Function Pass Manager' on module '<stdin>'. > >> 2. Running pass 'BPF DAG->DAG Pattern Instruction Selection' on function '@bpf_prog1' > >> #0 0x000000000183c26c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) > >> (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x183c26c) > >> ... > >> #7 0x00000000017c375e (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x17c375e) > >> #8 0x00000000016a75c5 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) > >> (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16a75c5) > >> #9 0x00000000016ab4f8 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, > >> unsigned int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16ab4f8) > >> ... > >> Aborted (core dumped) | llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o > >> > >> The reason is due to llvm change https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D87153&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=_D9tvuWQ6EbYqcMBdVB0qqRMVdV6Etws5ITtx8Pa1ZM&s=fo_LvXqHJx_m0m0pJJiDdOUcOzVXm2_iYoxPhpqpzng&e= > >> where the CORE relocation global generation is moved from the beginning > >> of target dependent optimization (llc) to the beginning > >> of target independent optimization (opt). > >> > >> Since samples/bpf programs did not use vmlinux.h and its clang compilation > >> uses native architecture, we need to adjust arch triple at opt level > >> to do CORE relocation global generation properly. Otherwise, the above > >> error will appear. > >> > >> This patch fixed the issue by introduce opt and llvm-dis to compilation chain, > >> which will do proper CORE relocation global generation as well as O2 level > >> optimization. Tested with llvm10, llvm11 and trunk/llvm12. > >> > >> Signed-off-by: Yonghong Song <yhs@fb.com> > >> --- > >> samples/bpf/Makefile | 6 +++++- > >> 1 file changed, 5 insertions(+), 1 deletion(-) > >> > >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > >> index 4f1ed0e3cf9f..79c5fdea63d2 100644 > >> --- a/samples/bpf/Makefile > >> +++ b/samples/bpf/Makefile > >> @@ -211,6 +211,8 @@ TPROGLDLIBS_xsk_fwd += -pthread > >> # make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang > >> LLC ?= llc > >> CLANG ?= clang > >> +OPT ?= opt > >> +LLVM_DIS ?= llvm-dis > >> LLVM_OBJCOPY ?= llvm-objcopy > >> BTF_PAHOLE ?= pahole > >> > >> @@ -314,7 +316,9 @@ $(obj)/%.o: $(src)/%.c > >> -Wno-address-of-packed-member -Wno-tautological-compare \ > >> -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ > >> -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ > >> - -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ > >> + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ > >> + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ > >> + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ This is an extremely unusual set of steps, and might be worthwhile to leave a comment explaining what's going on, so that I or someone else doesn't ask the same question few months later :) At any rate, this fixes the issue, so: Acked-by: Andrii Nakryiko <andrii@kernel.org> > > > > I keep forgetting exact details of why we do this native clang + llc > > pipeline instead of just doing `clang -target bpf`? Is it still > > samples/bpf programs did not use vmlinux.h. they directly use > kernel-devel headers, hence they need to first compile with native arch > for clang but later change target arch to bpf to generate final byte code. > They cannot just do 'clang -target bpf' without vmlinux.h. Ok, right, thanks for explanation. I wonder if this "native" clang + llc pass will also help with vmlinux.h on 32-bit architectures (though with my recent patches that shouldn't be necessary, so this is more of a curiosity, rather than the need). > > But changing to use vmlinux.h is a much bigger project and I merely > want to make it just work so people won't make/compile samples/bpf > and get compilation errors. Right, of course. > > > relevant and necessary, or we can just simplify it now? > > > >> ifeq ($(DWARF2BTF),y) > >> $(BTF_PAHOLE) -J $@ > >> endif > >> -- > >> 2.24.1 > >>
On 10/5/20 12:27 PM, Andrii Nakryiko wrote: > On Fri, Oct 2, 2020 at 10:16 PM Yonghong Song <yhs@fb.com> wrote: >> >> >> >> On 10/2/20 9:22 PM, Andrii Nakryiko wrote: >>> On Fri, Oct 2, 2020 at 7:19 PM Yonghong Song <yhs@fb.com> wrote: >>>> >>>> With latest llvm trunk, bpf programs under samples/bpf >>>> directory, if using CORE, may experience the following >>>> errors: >>>> >>>> LLVM ERROR: Cannot select: intrinsic %llvm.preserve.struct.access.index >>>> PLEASE submit a bug report to https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=_D9tvuWQ6EbYqcMBdVB0qqRMVdV6Etws5ITtx8Pa1ZM&s=BwTAvhipPl-Az_WaiJDbqU8yl__NvG8W4HmCqWqHdqg&e= and include the crash backtrace. >>>> Stack dump: >>>> 0. Program arguments: llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o >>>> 1. Running pass 'Function Pass Manager' on module '<stdin>'. >>>> 2. Running pass 'BPF DAG->DAG Pattern Instruction Selection' on function '@bpf_prog1' >>>> #0 0x000000000183c26c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) >>>> (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x183c26c) >>>> ... >>>> #7 0x00000000017c375e (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x17c375e) >>>> #8 0x00000000016a75c5 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) >>>> (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16a75c5) >>>> #9 0x00000000016ab4f8 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, >>>> unsigned int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16ab4f8) >>>> ... >>>> Aborted (core dumped) | llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o >>>> >>>> The reason is due to llvm change https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D87153&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=_D9tvuWQ6EbYqcMBdVB0qqRMVdV6Etws5ITtx8Pa1ZM&s=fo_LvXqHJx_m0m0pJJiDdOUcOzVXm2_iYoxPhpqpzng&e= >>>> where the CORE relocation global generation is moved from the beginning >>>> of target dependent optimization (llc) to the beginning >>>> of target independent optimization (opt). >>>> >>>> Since samples/bpf programs did not use vmlinux.h and its clang compilation >>>> uses native architecture, we need to adjust arch triple at opt level >>>> to do CORE relocation global generation properly. Otherwise, the above >>>> error will appear. >>>> >>>> This patch fixed the issue by introduce opt and llvm-dis to compilation chain, >>>> which will do proper CORE relocation global generation as well as O2 level >>>> optimization. Tested with llvm10, llvm11 and trunk/llvm12. >>>> >>>> Signed-off-by: Yonghong Song <yhs@fb.com> >>>> --- >>>> samples/bpf/Makefile | 6 +++++- >>>> 1 file changed, 5 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile >>>> index 4f1ed0e3cf9f..79c5fdea63d2 100644 >>>> --- a/samples/bpf/Makefile >>>> +++ b/samples/bpf/Makefile >>>> @@ -211,6 +211,8 @@ TPROGLDLIBS_xsk_fwd += -pthread >>>> # make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang >>>> LLC ?= llc >>>> CLANG ?= clang >>>> +OPT ?= opt >>>> +LLVM_DIS ?= llvm-dis >>>> LLVM_OBJCOPY ?= llvm-objcopy >>>> BTF_PAHOLE ?= pahole >>>> >>>> @@ -314,7 +316,9 @@ $(obj)/%.o: $(src)/%.c >>>> -Wno-address-of-packed-member -Wno-tautological-compare \ >>>> -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ >>>> -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ >>>> - -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ >>>> + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ >>>> + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ >>>> + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ > > This is an extremely unusual set of steps, and might be worthwhile to > leave a comment explaining what's going on, so that I or someone else > doesn't ask the same question few months later :) Sure. Will add some comments and send v2. > > At any rate, this fixes the issue, so: > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > >>> >>> I keep forgetting exact details of why we do this native clang + llc >>> pipeline instead of just doing `clang -target bpf`? Is it still >> >> samples/bpf programs did not use vmlinux.h. they directly use >> kernel-devel headers, hence they need to first compile with native arch >> for clang but later change target arch to bpf to generate final byte code. >> They cannot just do 'clang -target bpf' without vmlinux.h. > > Ok, right, thanks for explanation. I wonder if this "native" clang + > llc pass will also help with vmlinux.h on 32-bit architectures (though > with my recent patches that shouldn't be necessary, so this is more of > a curiosity, rather than the need). Yes, I think this should help 32-bit as all the 32-bit long/ptr size is captured in IR. I probably tried before with 32bit x86 uprobe, but I forgot details... > >> >> But changing to use vmlinux.h is a much bigger project and I merely >> want to make it just work so people won't make/compile samples/bpf >> and get compilation errors. > > Right, of course. > >> >>> relevant and necessary, or we can just simplify it now? >>> >>>> ifeq ($(DWARF2BTF),y) >>>> $(BTF_PAHOLE) -J $@ >>>> endif >>>> -- >>>> 2.24.1 >>>>
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index 4f1ed0e3cf9f..79c5fdea63d2 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile @@ -211,6 +211,8 @@ TPROGLDLIBS_xsk_fwd += -pthread # make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang LLC ?= llc CLANG ?= clang +OPT ?= opt +LLVM_DIS ?= llvm-dis LLVM_OBJCOPY ?= llvm-objcopy BTF_PAHOLE ?= pahole @@ -314,7 +316,9 @@ $(obj)/%.o: $(src)/%.c -Wno-address-of-packed-member -Wno-tautological-compare \ -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ - -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ ifeq ($(DWARF2BTF),y) $(BTF_PAHOLE) -J $@ endif
With latest llvm trunk, bpf programs under samples/bpf directory, if using CORE, may experience the following errors: LLVM ERROR: Cannot select: intrinsic %llvm.preserve.struct.access.index PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace. Stack dump: 0. Program arguments: llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o 1. Running pass 'Function Pass Manager' on module '<stdin>'. 2. Running pass 'BPF DAG->DAG Pattern Instruction Selection' on function '@bpf_prog1' #0 0x000000000183c26c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x183c26c) ... #7 0x00000000017c375e (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x17c375e) #8 0x00000000016a75c5 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16a75c5) #9 0x00000000016ab4f8 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16ab4f8) ... Aborted (core dumped) | llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o The reason is due to llvm change https://reviews.llvm.org/D87153 where the CORE relocation global generation is moved from the beginning of target dependent optimization (llc) to the beginning of target independent optimization (opt). Since samples/bpf programs did not use vmlinux.h and its clang compilation uses native architecture, we need to adjust arch triple at opt level to do CORE relocation global generation properly. Otherwise, the above error will appear. This patch fixed the issue by introduce opt and llvm-dis to compilation chain, which will do proper CORE relocation global generation as well as O2 level optimization. Tested with llvm10, llvm11 and trunk/llvm12. Signed-off-by: Yonghong Song <yhs@fb.com> --- samples/bpf/Makefile | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)