When compiling Rust code we may end up with calls to functions provided
by other code units. Presently this code crashes on a null pointer
dereference - this patch avoids that crash and adds a test.
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This error could be detected using the following test case:
$ cat test2.c ; ModuleID = 'test2.c' source_filename = "test2.c" target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128" target triple = "bpf" ; Function Attrs: noinline nounwind optnone define dso_local i64 @foo() { entry: ret i64 42 } !llvm.dbg.cu = !{!0} !llvm.module.flags = !{!2, !3, !4, !5} !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "foo", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None) !1 = !DIFile(filename: "file.c", directory: "/some/dir", checksumkind: CSK_MD5, checksum: "f58a7abbd9253986370acb1013fc9e55") !2 = !{i32 7, !"Dwarf Version", i32 5} !3 = !{i32 2, !"Debug Info Version", i32 3} !4 = !{i32 1, !"wchar_size", i32 4} !5 = !{i32 7, !"frame-pointer", i32 2} !6 = !{!"clang version 18.0.0 (/home/eddy/work/llvm-project/clang 61cd4a1d35aa7c0f7b312b8f43ed3bff33f20d55)"} $ llc test2.ll -o /dev/null /home/eddy/work/llvm-project/llvm/lib/Target/BPF/BTFDebug.cpp:1640:42: runtime error: member call on null pointer of type 'llvm::DISubprogram' SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/eddy/work/llvm-project/llvm/lib/Target/BPF/BTFDebug.cpp:1640:42 in
Necessary conditions are: module with debug attributes (llvm.dbg.cu -> DICompileUnit) and a function and instruction w/o debug metadata. I think such test case should be added to the suite.
Also, I don't see a point in reporting this (either as warning or as error). Absence of DISubprogram is ignored in BTFDebug::processFuncPrototypes and it two other places getSubprogram() can't return null. I think the following patch should suffice:
diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp index d886edaff555..6df421934b70 100644 --- a/llvm/lib/Target/BPF/BTFDebug.cpp +++ b/llvm/lib/Target/BPF/BTFDebug.cpp @@ -1634,8 +1635,8 @@ void BTFDebug::beginInstruction(const MachineInstr *MI) { if (!DL || PrevInstLoc == DL) { // This instruction will be skipped, no LineInfo has // been generated, construct one based on function signature. - if (LineInfoGenerated == false) { - auto *S = MI->getMF()->getFunction().getSubprogram(); + DISubprogram *S = MI->getMF()->getFunction().getSubprogram(); + if (!LineInfoGenerated && S) { MCSymbol *FuncLabel = Asm->getFunctionBegin(); constructLineInfo(S, FuncLabel, S->getLine(), 0); LineInfoGenerated = true;
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Sounds good! I'll do that. Can you share the C source code of the program as well please?
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// clang -g --target=bpf -S -emit-llvm test2.c -o - unsigned long foo(void) { return 42; }
Modified to remove !dbg from function and ret instructions.
llvm/lib/Target/BPF/BTFDebug.cpp | ||
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1377 | parens |
llvm/lib/Target/BPF/BTFDebug.cpp | ||
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1377 | Done. |
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