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[LLD][COFF] Fix writing a map file when range extension thunks are inserted

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Bug: An assertion fails:

    Assertion failed: isa<To>(Val) && "cast<Ty>() argument of incompatible type!",
    file C:\Users\<user>\prog\llvm\llvm-git-lld-bug\llvm\include\llvm/Support/Casting.h, line 578

Bug is triggered, if

    - a map file is requested with /MAP, and
    - Architecture is ARMv7, Thumb, and
    - a relative jump (branch instruction) is greater than 16 MiB (2^24)

The reason for the Bug is:

    - a Thunk is created for the jump
    - a Symbol for the Thunk is created
        - of type `DefinedSynthetic`
        - in file `Writer.cpp`
        - in function `getThunk`
    - the Symbol has no name
    - when creating the map file, the name of the Symbol is queried
    - the function `Symbol::computeName` of the base class `Symbol`
      casts the `this` pointer to type `DefinedCOFF` (a derived type),
      but the acutal type is `DefinedSynthetic`
    - The in the llvm::cast an assertion fails

Changes:

- Modify regression test to trigger this bug
- Give the symbol pointing to the thunk a name, to fix the bug
- Add assertion, that only DefinedCOFF symbols are allowed to have an
  empty name, when the constructor of the base class Symbol is executed

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D133201
This commit is contained in:
Jan Ole Hüser
2022-09-07 09:17:10 +03:00
committed by Martin Storsjö
parent ea953b9d9a
commit 4e5a59a383
4 changed files with 7 additions and 4 deletions
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5
lld/COFF/Symbols.h
View File

@@ -106,7 +106,10 @@ protected:
: symbolKind(k), isExternal(true), isCOMDAT(false),
writtenToSymtab(false), pendingArchiveLoad(false), isGCRoot(false),
isRuntimePseudoReloc(false), deferUndefined(false), canInline(true),
nameSize(n.size()), nameData(n.empty() ? nullptr : n.data()) {}
nameSize(n.size()), nameData(n.empty() ? nullptr : n.data()) {
assert((!n.empty() || k <= LastDefinedCOFFKind) &&
"If the name is empty, the Symbol must be a DefinedCOFF.");
}
const unsigned symbolKind : 8;
unsigned isExternal : 1;

2
lld/COFF/Writer.cpp
View File

@@ -396,7 +396,7 @@ getThunk(DenseMap<uint64_t, Defined *> &lastThunks, Defined *target, uint64_t p,
default:
llvm_unreachable("Unexpected architecture");
}
Defined *d = make<DefinedSynthetic>("", c);
Defined *d = make<DefinedSynthetic>("range_extension_thunk", c);
lastThunk = d;
return {d, true};
}

2
lld/test/COFF/arm-thumb-thunks.s
View File

@@ -1,6 +1,6 @@
// REQUIRES: arm
// RUN: llvm-mc -filetype=obj -triple=thumbv7-windows %s -o %t.obj
// RUN: lld-link -entry:main -subsystem:console %t.obj -out:%t.exe -verbose 2>&1 | FileCheck -check-prefix=VERBOSE %s
// RUN: lld-link -entry:main -subsystem:console %t.obj -out:%t.exe -map -verbose 2>&1 | FileCheck -check-prefix=VERBOSE %s
// RUN: llvm-objdump -d %t.exe --start-address=0x401000 --stop-address=0x401022 | FileCheck --check-prefix=MAIN %s
// RUN: llvm-objdump -d %t.exe --start-address=0x501022 --stop-address=0x501032 | FileCheck --check-prefix=FUNC1 %s
// RUN: llvm-objdump -d %t.exe --start-address=0x601032 | FileCheck --check-prefix=FUNC2 %s

2
lld/test/COFF/arm64-thunks.s
View File

@@ -1,6 +1,6 @@
// REQUIRES: aarch64
// RUN: llvm-mc -filetype=obj -triple=aarch64-windows %s -o %t.obj
// RUN: lld-link -entry:main -subsystem:console %t.obj -out:%t.exe -verbose 2>&1 | FileCheck -check-prefix=VERBOSE %s
// RUN: lld-link -entry:main -subsystem:console %t.obj -out:%t.exe -map -verbose 2>&1 | FileCheck -check-prefix=VERBOSE %s
// RUN: llvm-objdump -d %t.exe | FileCheck --check-prefix=DISASM %s
// VERBOSE: Added 2 thunks with margin {{.*}} in 1 passes