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https://github.com/c64scene-ar/llvm-6502.git
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61253a9c93
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5255 91177308-0d34-0410-b5e6-96231b3b80d8
70 lines
2.3 KiB
C++
70 lines
2.3 KiB
C++
//===-- Callback.cpp - Trap handler for function resolution ---------------===//
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//
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// This file defines the SIGSEGV handler which is invoked when a reference to a
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// non-codegen'd function is found.
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//
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//===----------------------------------------------------------------------===//
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#include "VM.h"
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#include "Support/Statistic.h"
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#include <signal.h>
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#include <ucontext.h>
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#include <iostream>
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static VM *TheVM = 0;
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static void TrapHandler(int TN, siginfo_t *SI, ucontext_t *ucp) {
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assert(TN == SIGSEGV && "Should be SIGSEGV!");
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#ifdef REG_EIP /* this code does not compile on Sparc! */
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if (SI->si_code != SEGV_MAPERR || SI->si_addr != 0 ||
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ucp->uc_mcontext.gregs[REG_EIP] != 0) {
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std::cerr << "Bad SEGV encountered EIP = 0x" << std::hex
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<< ucp->uc_mcontext.gregs[REG_EIP] << " addr = "
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<< SI->si_addr << "!\n";
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struct sigaction SA; // Restore old SEGV handler...
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SA.sa_handler = SIG_DFL;
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SA.sa_flags = SA_NOMASK;
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sigaction(SIGSEGV, &SA, 0);
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return; // Should core dump now...
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}
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// The call instruction should have pushed the return value onto the stack...
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unsigned RefAddr = *(unsigned*)ucp->uc_mcontext.gregs[REG_ESP];
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RefAddr -= 4; // Backtrack to the reference itself...
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DEBUG(std::cerr << "In SEGV handler! Addr=0x" << std::hex << RefAddr
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<< " ESP=0x" << ucp->uc_mcontext.gregs[REG_ESP] << std::dec
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<< ": Resolving call to function: "
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<< TheVM->getFunctionReferencedName((void*)RefAddr) << "\n");
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// Sanity check to make sure this really is a call instruction...
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assert(((unsigned char*)RefAddr)[-1] == 0xE8 && "Not a call instr!");
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unsigned NewVal = (unsigned)TheVM->resolveFunctionReference((void*)RefAddr);
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// Rewrite the call target... so that we don't fault every time we execute
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// the call.
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*(unsigned*)RefAddr = NewVal-RefAddr-4;
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// Change the instruction pointer to be the real target of the call...
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ucp->uc_mcontext.gregs[REG_EIP] = NewVal;
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#endif
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}
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void VM::registerCallback() {
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TheVM = this;
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// Register the signal handler...
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struct sigaction SA;
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SA.sa_sigaction = (void (*)(int, siginfo_t*, void*))TrapHandler;
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sigfillset(&SA.sa_mask); // Block all signals while codegen'ing
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SA.sa_flags = SA_NOCLDSTOP|SA_SIGINFO; // Get siginfo
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sigaction(SIGSEGV, &SA, 0); // Install the handler
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}
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