Clang crashes when compiling MIPS kernel

[tpimh]

0.	Program arguments: /usr/lib/llvm-9/bin/clang -cc1 -triple mipsel-unknown-linux-gnu -S -disable-free -disable-llvm-verifier -discard-value-names -main-file-name ioctl.c -mrelocation-model static -mthread-model posix -fno-delete-null-pointer-checks -mllvm -warn-stack-size=1024 -relaxed-aliasing -fmath-errno -masm-verbose -no-integrated-as -mconstructor-aliases -ffreestanding -fuse-init-array -target-cpu mips32r2 -target-feature +noabicalls -target-feature +soft-float -target-abi o32 -msoft-float -mfloat-abi soft -mllvm -mno-check-zero-division -mllvm -mips-ssection-threshold=0 -mllvm -mgpopt -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -coverage-notes-file /continuous-integration/linux/fs/ext4/ioctl.gcno -nostdsysteminc -nobuiltininc -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -isystem /usr/lib/llvm-9/lib/clang/9.0.0/include -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -I ./arch/mips/include -I ./arch/mips/include/generated -I ./include -I ./arch/mips/include/uapi -I ./arch/mips/include/generated/uapi -I ./include/uapi -I ./include/generated/uapi -D __KERNEL__ -D VMLINUX_LOAD_ADDRESS=0xffffffff80100000 -D DATAOFFSET=0 -D GAS_HAS_SET_HARDFLOAT -D TOOLCHAIN_SUPPORTS_VIRT -D TOOLCHAIN_SUPPORTS_CRC -D TOOLCHAIN_SUPPORTS_DSP -D TOOLCHAIN_SUPPORTS_GINV -I ./arch/mips/include/asm/mach-malta -I ./arch/mips/include/asm/mach-generic -D KBUILD_BASENAME="ioctl" -D KBUILD_MODNAME="ext4" -O2 -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -Werror=implicit-function-declaration -Werror=implicit-int -Wno-format-security -Wno-address-of-packed-member -Wno-format-invalid-specifier -Wno-gnu -Wno-tautological-compare -Wno-unused-const-variable -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Werror=date-time -Werror=incompatible-pointer-types -Wno-initializer-overrides -Wno-unused-value -Wno-format -Wno-sign-compare -Wno-format-zero-length -Wno-uninitialized -std=gnu89 -fno-dwarf-directory-asm -fdebug-compilation-dir /continuous-integration/linux -ferror-limit 19 -fmessage-length 0 -fwrapv -stack-protector 2 -fwchar-type=short -fno-signed-wchar -fobjc-runtime=gcc -fno-common -fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops -vectorize-slp -o /tmp/ioctl-501db4.s -x c fs/ext4/ioctl.c 
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module 'fs/ext4/ioctl.c'.
4.	Running pass 'MIPS DAG->DAG Pattern Instruction Selection' on function '@ext4_ioctl'
 #0 0x00007f7b606524ff llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xb394ff)
 #1 0x00007f7b60650940 llvm::sys::RunSignalHandlers() (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xb37940)
 #2 0x00007f7b60652901 (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xb39901)
 #3 0x00007f7b63c8f730 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12730)
 #4 0x00007f7b61ec2753 llvm::MipsSEDAGToDAGISel::SelectInlineAsmMemoryOperand(llvm::SDValue const&, unsigned int, std::vector<llvm::SDValue, std::allocator<llvm::SDValue> >&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x23a9753)
 #5 0x00007f7b60c060b7 llvm::SelectionDAGISel::SelectInlineAsmMemoryOperands(std::vector<llvm::SDValue, std::allocator<llvm::SDValue> >&, llvm::SDLoc const&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x10ed0b7)
 #6 0x00007f7b60c06a14 llvm::SelectionDAGISel::Select_INLINEASM(llvm::SDNode*, bool) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x10eda14)
 #7 0x00007f7b60c03ac7 llvm::SelectionDAGISel::DoInstructionSelection() (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x10eaac7)
 #8 0x00007f7b60c03170 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x10ea170)
 #9 0x00007f7b60c02837 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x10e9837)
#10 0x00007f7b60c00226 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x10e7226)
#11 0x00007f7b61e900da llvm::MipsDAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0x23770da)
#12 0x00007f7b608d6428 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xdbd428)
#13 0x00007f7b6074ecf6 llvm::FPPassManager::runOnFunction(llvm::Function&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xc35cf6)
#14 0x00007f7b6074efa3 llvm::FPPassManager::runOnModule(llvm::Module&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xc35fa3)
#15 0x00007f7b6074f44a llvm::legacy::PassManagerImpl::run(llvm::Module&) (/usr/lib/x86_64-linux-gnu/libLLVM-9.so.1+0xc3644a)
#16 0x00000000007253a6 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::DataLayout const&, llvm::Module*, clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream> >) (/usr/lib/llvm-9/bin/clang+0x7253a6)
#17 0x0000000000de35fd (/usr/lib/llvm-9/bin/clang+0xde35fd)
#18 0x0000000001296133 clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm-9/bin/clang+0x1296133)
#19 0x0000000000b5b28f clang::FrontendAction::Execute() (/usr/lib/llvm-9/bin/clang+0xb5b28f)
#20 0x0000000000b181b1 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/llvm-9/bin/clang+0xb181b1)
#21 0x0000000000be4d60 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm-9/bin/clang+0xbe4d60)
#22 0x00000000006eda30 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/lib/llvm-9/bin/clang+0x6eda30)
#23 0x00000000006ebe40 main (/usr/lib/llvm-9/bin/clang+0x6ebe40)
#24 0x00007f7b5f65b09b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2409b)
#25 0x00000000006e917a _start (/usr/lib/llvm-9/bin/clang+0x6e917a)
clang: error: unable to execute command: Segmentation fault (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 9.0.0-svn364127-1~exp1+0~20190622095755.118~1.gbp9b9451 (trunk)
Target: mipsel-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
clang: note: diagnostic msg: PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
clang: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /tmp/ioctl-8c74cc.c
clang: note: diagnostic msg: /tmp/ioctl-8c74cc.sh
clang: note: diagnostic msg: 

********************

ioctl-8c74cc.zip

[nickdesaulniers]

Needs to be creduce'd; ext4_ioctl is problematic somehow.

[nathanchance]

@tpimh what defconfig are you using?

[nathanchance]

I assumed it was 32r2el_defconfig based on the flags.

creduce spits out:

a() { __asm__("" : "=ro"(*(int *)0)); }

with the following interestingness case:

#!/bin/bash

mipsel-linux-gnu-gcc -O2 -c -o /dev/null ioctl.i || exit 1

clang-9 -Qunused-arguments -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE -std=gnu89 --target=mipsel-linux-gnu --prefix=/usr/bin/ --gcc-toolchain=/usr -no-integrated-as -mno-check-zero-division -mabi=32 -G 0 -mno-abicalls -fno-pic -pipe -msoft-float -Wa,-msoft-float -ffreestanding -EL -fno-stack-check -march=mips32r2 -Wa,--trap -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -O2 -fstack-protector-strong -mno-global-merge -fomit-frame-pointer -g -fno-var-tracking -fno-strict-overflow -fno-merge-all-constants -fno-stack-check -c -o /dev/null ioctl.i |& grep "llvm::MipsSEDAGToDAGISel::SelectInlineAsmMemoryOperand"

This occurs on tip of tree clang-9 and llvmorg-8.0.1-rc3.

[tpimh]

If I recall correctly it was malta_defconfig(or maybe malta_qemu_32r6_defconfig).

[nickdesaulniers]

@nathanchance nice find. Please file a bug in upstream llvm's issue tracker.

[nathanchance]

Will do.

[nathanchance]

https://llvm.org/pr42589

[nathanchance]

Fixed: llvm/llvm-project@7f308af

I'll build and test here shortly.

[nathanchance]

After fixing some warnings/errors (which I will be filing issues and sending patches for), I can compile and link a malta_defconfig kernel.

[nickdesaulniers]

I can compile and link a malta_defconfig kernel.

Does it boot?

[nathanchance]

Have not tested since we don't have a buildroot image for it yet

[tpimh]

If it panics because of no init, should be good enough to proceed.

[nathanchance]

That’s a fair point, I will try later tonight.

[nickdesaulniers]

If it panics because of no init, should be good enough to proceed.

Yep, that's usually a good sign.

[nathanchance]

See #610 for follow up on booting the kernel.