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Respect Addend when processing MCJIT relocations to local/global symbols.

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When the RuntimeDyldELF::processRelocationRef routine finds the target
symbol of a relocation in the local or global symbol table, it performs
a section-relative relocation:

    Value.SectionID = lsi->second.first;
    Value.Addend = lsi->second.second;

At this point, however, any Addend that might have been specified in
the original relocation record is lost.  This is somewhat difficult to
trigger for relocations within the code section since they usually
do not contain non-zero Addends (when built with the default JIT code
model, in any case).  However, the problem can be reliably triggered
by a relocation within the data section caused by code like:

 int test[2] = { -1, 0 };
 int *p = &test[1];

The initializer of "p" will need a relocation to "test + 4".  On
platforms using RelA relocations this means an Addend of 4 is required.
Current code ignores this addend when processing the relocation,
resulting in incorrect execution.

Fixed by taking the Addend into account when processing relocations
to symbols found in the local or global symbol table.

Tested on x86_64-linux and powerpc64-linux.

llvm-svn: 178869
This commit is contained in:
Ulrich Weigand 2013-04-05 13:29:04 +00:00
parent 5cf62b262f
commit 045c5fae3d
2 changed files with 27 additions and 2 deletions
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4
lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
View File

@ -617,14 +617,14 @@ void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
Symbol.getType(SymType);
if (lsi != Symbols.end()) {
Value.SectionID = lsi->second.first;
Value.Addend = lsi->second.second;
Value.Addend = lsi->second.second + Addend;
} else {
// Search for the symbol in the global symbol table
SymbolTableMap::const_iterator gsi =
GlobalSymbolTable.find(TargetName.data());
if (gsi != GlobalSymbolTable.end()) {
Value.SectionID = gsi->second.first;
Value.Addend = gsi->second.second;
Value.Addend = gsi->second.second + Addend;
} else {
switch (SymType) {
case SymbolRef::ST_Debug: {

25
test/ExecutionEngine/MCJIT/2013-04-04-RelocAddend.ll Normal file
View File

@ -0,0 +1,25 @@
; RUN: %lli_mcjit %s
;
; Verify relocations to global symbols with addend work correctly.
;
; Compiled from this C code:
;
; int test[2] = { -1, 0 };
; int *p = &test[1];
;
; int main (void)
; {
; return *p;
; }
;
@test = global [2 x i32] [i32 -1, i32 0], align 4
@p = global i32* getelementptr inbounds ([2 x i32]* @test, i64 0, i64 1), align 8
define i32 @main() {
entry:
%0 = load i32** @p, align 8
%1 = load i32* %0, align 4
ret i32 %1
}