diff options
Diffstat (limited to 'lib/ExecutionEngine/JIT/Callback.cpp')
-rw-r--r-- | lib/ExecutionEngine/JIT/Callback.cpp | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/lib/ExecutionEngine/JIT/Callback.cpp b/lib/ExecutionEngine/JIT/Callback.cpp new file mode 100644 index 0000000000..b843e10689 --- /dev/null +++ b/lib/ExecutionEngine/JIT/Callback.cpp @@ -0,0 +1,62 @@ +//===-- Callback.cpp - Trap handler for function resolution ---------------===// +// +// This file defines the SIGSEGV handler which is invoked when a reference to a +// non-codegen'd function is found. +// +//===----------------------------------------------------------------------===// + +#include "VM.h" +#include "Support/Statistic.h" +#include <signal.h> +#include <ucontext.h> +#include <iostream> + +static VM *TheVM = 0; + +static void TrapHandler(int TN, siginfo_t *SI, ucontext_t *ucp) { + assert(TN == SIGSEGV && "Should be SIGSEGV!"); + +#ifdef REG_EIP /* this code does not compile on Sparc! */ + if (SI->si_code != SEGV_MAPERR || SI->si_addr != 0 || + ucp->uc_mcontext.gregs[REG_EIP] != 0) { + std::cerr << "Bad SEGV encountered!\n"; + abort(); + } + + // The call instruction should have pushed the return value onto the stack... + unsigned RefAddr = *(unsigned*)ucp->uc_mcontext.gregs[REG_ESP]; + RefAddr -= 4; // Backtrack to the reference itself... + + DEBUG(std::cerr << "In SEGV handler! Addr=0x" << std::hex << RefAddr + << " ESP=0x" << ucp->uc_mcontext.gregs[REG_ESP] << std::dec + << ": Resolving call to function: " + << TheVM->getFunctionReferencedName((void*)RefAddr) << "\n"); + + // Sanity check to make sure this really is a call instruction... + assert(((unsigned char*)RefAddr)[-1] == 0xE8 && "Not a call instr!"); + + unsigned NewVal = (unsigned)TheVM->resolveFunctionReference((void*)RefAddr); + + // Rewrite the call target... so that we don't fault every time we execute + // the call. + *(unsigned*)RefAddr = NewVal-RefAddr-4; + + // Change the instruction pointer to be the real target of the call... + ucp->uc_mcontext.gregs[REG_EIP] = NewVal; + +#endif +} + + +void VM::registerCallback() { + TheVM = this; + + // Register the signal handler... + struct sigaction SA; + SA.sa_sigaction = (void (*)(int, siginfo_t*, void*))TrapHandler; + sigfillset(&SA.sa_mask); // Block all signals while codegen'ing + SA.sa_flags = SA_NOCLDSTOP|SA_SIGINFO; // Get siginfo + sigaction(SIGSEGV, &SA, 0); // Install the handler +} + + |