mirror of
https://github.com/revng/revng
synced 2026-06-21 14:07:57 +00:00
Alessandro Di Federico
91 lines
3.3 KiB
C++
91 lines
3.3 KiB
C++
#pragma once
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//
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// This file is distributed under the MIT License. See LICENSE.md for details.
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//
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#include <vector>
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/Pass.h"
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#include "revng/Model/Binary.h"
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class ProgramCounterHandler;
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/// \brief Inject code to support jumping in non-translated code and handling
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/// the comeback.
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///
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/// This pass changes the default case of the dispatcher by checking if you're
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/// trying to jump to an address that is not in one of the executable segments.
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/// If so, the relevant a setjmp is performed, the CPU state is serialized to
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/// the actual phsyical registers and then a jump to the target address is
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/// performed. At this point the jump might be successful or it might fail.
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///
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/// Symmetrically, with the help of support.c, a signal handler is installed
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/// which detects segmentation faults and checks if an attempt to jump to an
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/// executable segment was performed.
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/// If this is the case, we perform a longjmp to get back into the proper
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/// context, we restore the relevant registers from the data structures provided
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/// by the signal handler and then jump to the dispatcher to resume execution.
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class ExternalJumpsHandler {
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private:
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const model::Binary &Model;
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llvm::LLVMContext &Context;
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QuickMetadata QMD;
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llvm::Module &TheModule;
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llvm::Function &TheFunction;
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llvm::BasicBlock *Dispatcher;
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ProgramCounterHandler *PCH;
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public:
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/// \param TheFunction the root function.
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ExternalJumpsHandler(const model::Binary &Model,
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llvm::BasicBlock *Dispatcher,
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llvm::Function &TheFunction,
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ProgramCounterHandler *PCH);
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public:
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/// \brief Creates the jump out and jump back in handling infrastructure.
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void createExternalJumpsHandler();
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private:
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/// \brief Create the basic blocks to handle jumping to external code.
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///
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/// Prepare serialize_and_jump_out, which writes in physical registers the
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/// values of all ABI-related CSVs and then blindly jumps to the content of
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/// the program counter CSV.
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llvm::BasicBlock *createSerializeAndJumpOut();
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/// \brief Create the setjump basic block.
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///
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/// This basic block will perform a setjmp to save the context (the stack
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/// pointer in particular) and then go to serialize_and_jump_out.
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/// The second return of setjmp instead will deserialize the CPU state and go
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/// back to the dispatcher.
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llvm::BasicBlock *
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createSetjmp(llvm::BasicBlock *FirstReturn, llvm::BasicBlock *SecondReturn);
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/// \brief Prepare a list of the executable segments that can be easily
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/// consumed by support.c.
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///
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/// This method creates three global variables:
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///
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/// * an unamed array of uint64_t large as twice the number of executable
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/// segments, where the even entries contain the start address of a segment
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/// and odd ones the end address.
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/// * "segment_boundaries": a `uint64_t *` targeting the previous array.
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/// * "segments_count": an uint64_t containing the number of executable
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/// segments.
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void buildExecutableSegmentsList();
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/// \brief Creates the basic block taking care of deserializing the CPU state
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/// to the CSVs.
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///
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/// The CPU state is restored from the mcontext_t field in the struct provided
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/// by the kernel to the signal handler.
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llvm::BasicBlock *createReturnFromExternal();
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};
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