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Implement trampoline step-through for Windows-x86.

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Summary:
This is required to be able to step through calls to external functions
that are not properly marked with __declspec(dllimport). When a call
like this is emitted, the linker will inject a trampoline to produce an
indirect call through the IAT.

Reviewers: zturner, jingham

Reviewed By: jingham

Subscribers: sas, jingham, lldb-commits

Differential Revision: https://reviews.llvm.org/D22231

llvm-svn: 314045
This commit is contained in:
Stephane Sezer
2017-09-22 23:41:41 +00:00
parent 3477711ec7
commit 85317f23df
1 changed files with 43 additions and 1 deletions
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44
lldb/source/Plugins/DynamicLoader/Windows-DYLD/DynamicLoaderWindowsDYLD.cpp
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@@ -11,8 +11,11 @@
#include "DynamicLoaderWindowsDYLD.h"
#include "lldb/Core/PluginManager.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/ThreadPlanStepInstruction.h"
#include "llvm/ADT/Triple.h"
@@ -72,5 +75,44 @@ uint32_t DynamicLoaderWindowsDYLD::GetPluginVersion() { return 1; }
ThreadPlanSP
DynamicLoaderWindowsDYLD::GetStepThroughTrampolinePlan(Thread &thread,
bool stop) {
return ThreadPlanSP();
auto arch = m_process->GetTarget().GetArchitecture();
if (arch.GetMachine() != llvm::Triple::x86) {
return ThreadPlanSP();
}
uint64_t pc = thread.GetRegisterContext()->GetPC();
// Max size of an instruction in x86 is 15 bytes.
AddressRange range(pc, 2 * 15);
ExecutionContext exe_ctx(m_process->GetTarget());
DisassemblerSP disassembler_sp = Disassembler::DisassembleRange(
arch, nullptr, nullptr, exe_ctx, range, true);
if (!disassembler_sp) {
return ThreadPlanSP();
}
InstructionList *insn_list = &disassembler_sp->GetInstructionList();
if (insn_list == nullptr) {
return ThreadPlanSP();
}
// First instruction in a x86 Windows trampoline is going to be an indirect
// jump through the IAT and the next one will be a nop (usually there for
// alignment purposes). e.g.:
// 0x70ff4cfc <+956>: jmpl *0x7100c2a8
// 0x70ff4d02 <+962>: nop
auto first_insn = insn_list->GetInstructionAtIndex(0);
auto second_insn = insn_list->GetInstructionAtIndex(1);
if (first_insn == nullptr || second_insn == nullptr ||
strcmp(first_insn->GetMnemonic(&exe_ctx), "jmpl") != 0 ||
strcmp(second_insn->GetMnemonic(&exe_ctx), "nop") != 0) {
return ThreadPlanSP();
}
assert(first_insn->DoesBranch() && !second_insn->DoesBranch());
return ThreadPlanSP(new ThreadPlanStepInstruction(
thread, false, false, eVoteNoOpinion, eVoteNoOpinion));
}