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MC CFG: Add "dynamic disassembly" support to MCObjectDisassembler.

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It can now disassemble code in situations where the effective load
address is different than the load address declared in the object file.
This happens for PIC, hence "dynamic".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188884 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ahmed Bougacha 2013-08-21 07:28:37 +00:00
parent 46937278fa
commit 484a6eb9cc
2 changed files with 27 additions and 1 deletions
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16
include/llvm/MC/MCObjectDisassembler.h
View File

@ -65,6 +65,22 @@ public:
virtual ArrayRef<uint64_t> getStaticExitFunctions();
/// @}
/// \name Translation between effective and objectfile load address.
/// @{
/// \brief Compute the effective load address, from an objectfile virtual
/// address. This is implemented in a format-specific way, to take into
/// account things like PIE/ASLR when doing dynamic disassembly.
/// For example, on Mach-O this would be done by adding the VM addr slide,
/// on glibc ELF by keeping a map between segment load addresses, filled
/// using dl_iterate_phdr, etc..
/// In most static situations and in the default impl., this returns \p Addr.
virtual uint64_t getEffectiveLoadAddr(uint64_t Addr);
/// \brief Compute the original load address, as specified in the objectfile.
/// This is the inverse of getEffectiveLoadAddr.
virtual uint64_t getOriginalLoadAddr(uint64_t EffectiveAddr);
/// @}
protected:
const object::ObjectFile &Obj;
const MCDisassembler &Dis;

12
lib/MC/MCObjectDisassembler.cpp
View File

@ -44,7 +44,7 @@ uint64_t MCObjectDisassembler::getEntrypoint() {
if (Name == "main" || Name == "_main") {
uint64_t Entrypoint;
SI->getAddress(Entrypoint);
return Entrypoint;
return getEffectiveLoadAddr(Entrypoint);
}
}
return 0;
@ -58,6 +58,14 @@ ArrayRef<uint64_t> MCObjectDisassembler::getStaticExitFunctions() {
return ArrayRef<uint64_t>();
}
uint64_t MCObjectDisassembler::getEffectiveLoadAddr(uint64_t Addr) {
return Addr;
}
uint64_t MCObjectDisassembler::getOriginalLoadAddr(uint64_t Addr) {
return Addr;
}
MCModule *MCObjectDisassembler::buildEmptyModule() {
MCModule *Module = new MCModule;
Module->Entrypoint = getEntrypoint();
@ -90,6 +98,7 @@ void MCObjectDisassembler::buildSectionAtoms(MCModule *Module) {
uint64_t SecSize; SI->getSize(SecSize);
if (StartAddr == UnknownAddressOrSize || SecSize == UnknownAddressOrSize)
continue;
StartAddr = getEffectiveLoadAddr(StartAddr);
StringRef Contents; SI->getContents(Contents);
StringRefMemoryObject memoryObject(Contents, StartAddr);
@ -170,6 +179,7 @@ void MCObjectDisassembler::buildCFG(MCModule *Module) {
if (SymType == SymbolRef::ST_Function) {
uint64_t SymAddr;
SI->getAddress(SymAddr);
SymAddr = getEffectiveLoadAddr(SymAddr);
Calls.insert(SymAddr);
Splits.insert(SymAddr);
}