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MC/Mach-O/x86_64: Darwin's special "signed_N" relocation types should only be

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used to replace a normal relocation, not a reference to a GOT entry.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103789 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Dunbar
2010-05-14 18:53:40 +00:00
parent 4ed1082683
commit f0f6cdb6b4
2 changed files with 80 additions and 74 deletions
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46
lib/MC/MachObjectWriter.cpp
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@@ -609,10 +609,31 @@ public:
Type = RIT_X86_64_GOTLoad;
else
Type = RIT_X86_64_GOT;
} else if (Modifier != MCSymbolRefExpr::VK_None)
} else if (Modifier != MCSymbolRefExpr::VK_None) {
report_fatal_error("unsupported symbol modifier in relocation");
else
} else {
Type = RIT_X86_64_Signed;
// The Darwin x86_64 relocation format has a problem where it cannot
// encode an address (L<foo> + <constant>) which is outside the atom
// containing L<foo>. Generally, this shouldn't occur but it does
// happen when we have a RIPrel instruction with data following the
// relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
// adjustment Darwin x86_64 uses, the offset is still negative and
// the linker has no way to recognize this.
//
// To work around this, Darwin uses several special relocation types
// to indicate the offsets. However, the specification or
// implementation of these seems to also be incomplete; they should
// adjust the addend as well based on the actual encoded instruction
// (the additional bias), but instead appear to just look at the
// final offset.
switch (-(Target.getConstant() + (1LL << Log2Size))) {
case 1: Type = RIT_X86_64_Signed1; break;
case 2: Type = RIT_X86_64_Signed2; break;
case 4: Type = RIT_X86_64_Signed4; break;
}
}
} else {
if (Modifier != MCSymbolRefExpr::VK_None)
report_fatal_error("unsupported symbol modifier in branch "
@@ -620,27 +641,6 @@ public:
Type = RIT_X86_64_Branch;
}
// The Darwin x86_64 relocation format has a problem where it cannot
// encode an address (L<foo> + <constant>) which is outside the atom
// containing L<foo>. Generally, this shouldn't occur but it does happen
// when we have a RIPrel instruction with data following the relocation
// entry (e.g., movb $012, L0(%rip)). Even with the PCrel adjustment
// Darwin x86_64 uses, the offset is still negative and the linker has
// no way to recognize this.
//
// To work around this, Darwin uses several special relocation types to
// indicate the offsets. However, the specification or implementation of
// these seems to also be incomplete; they should adjust the addend as
// well based on the actual encoded instruction (the additional bias),
// but instead appear to just look at the final offset.
if (IsRIPRel) {
switch (-(Target.getConstant() + (1LL << Log2Size))) {
case 1: Type = RIT_X86_64_Signed1; break;
case 2: Type = RIT_X86_64_Signed2; break;
case 4: Type = RIT_X86_64_Signed4; break;
}
}
} else {
if (Modifier == MCSymbolRefExpr::VK_GOT) {
Type = RIT_X86_64_GOT;