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Fix a Mach-O assembler segfault for a subtraction expression with an undefined symbol. 

In a Mach-O object file a relocatable expression of the form
SymbolA - SymbolB + constant is allowed when both symbols are
defined in a section.  But when either symbol is undefined it
is an error.

The code was crashing when it had an undefined symbol in this case.
And should have printed a error message using the location information
in the relocation entry.

rdar://18678402

llvm-svn: 220599
This commit is contained in:
Kevin Enderby 2014-10-24 22:39:40 +00:00
parent 4183dbcc03
commit 2813f496d9
3 changed files with 19 additions and 4 deletions
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11
llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
View File

@ -179,11 +179,14 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
if (A_Base == B_Base && A_Base)
report_fatal_error("unsupported relocation with identical base", false);
// A subtraction expression where both symbols are undefined is a
// A subtraction expression where either symbol is undefined is a
// non-relocatable expression.
if (A->isUndefined() && B->isUndefined())
report_fatal_error("unsupported relocation with subtraction expression",
false);
if (A->isUndefined() || B->isUndefined()) {
StringRef Name = A->isUndefined() ? A->getName() : B->getName();
Asm.getContext().FatalError(Fixup.getLoc(),
"unsupported relocation with subtraction expression, symbol '" +
Name + "' can not be undefined in a subtraction expression");
}
Value += Writer->getSymbolAddress(&A_SD, Layout) -
(!A_Base ? 0 : Writer->getSymbolAddress(A_Base, Layout));

6
llvm/test/MC/MachO/bad-darwin-x86_64-reloc-expr1.s Normal file
View File

@ -0,0 +1,6 @@
// RUN: not llvm-mc -triple x86_64-apple-darwin10 %s -filetype=obj -o - 2> %t.err > %t
// RUN: FileCheck --check-prefix=CHECK-ERROR < %t.err %s
_Z:
.long (_Z+4)-_b
// CHECK-ERROR: error: unsupported relocation with subtraction expression, symbol '_b' can not be undefined in a subtraction expression

6
llvm/test/MC/MachO/bad-darwin-x86_64-reloc-expr2.s Normal file
View File

@ -0,0 +1,6 @@
// RUN: not llvm-mc -triple x86_64-apple-darwin10 %s -filetype=obj -o - 2> %t.err > %t
// RUN: FileCheck --check-prefix=CHECK-ERROR < %t.err %s
_Z:
.long (_a+4)-_Z
// CHECK-ERROR: error: unsupported relocation with subtraction expression, symbol '_a' can not be undefined in a subtraction expression