135 lines
5.1 KiB
C++
135 lines
5.1 KiB
C++
//===-- working_set_posix.cpp -----------------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of EfficiencySanitizer, a family of performance tuners.
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//
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// POSIX-specific working set tool code.
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//===----------------------------------------------------------------------===//
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#include "working_set.h"
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#include "esan_flags.h"
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#include "esan_shadow.h"
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#include "sanitizer_common/sanitizer_common.h"
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#include "sanitizer_common/sanitizer_linux.h"
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#include <signal.h>
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#include <sys/mman.h>
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namespace __esan {
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// We only support regular POSIX threads with a single signal handler
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// for the whole process == thread group.
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// Thus we only need to store one app signal handler.
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// FIXME: Store and use any alternate stack and signal flags set by
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// the app. For now we just call the app handler from our handler.
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static __sanitizer_sigaction AppSigAct;
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bool processWorkingSetSignal(int SigNum, void (*Handler)(int),
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void (**Result)(int)) {
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VPrintf(2, "%s: %d\n", __FUNCTION__, SigNum);
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if (SigNum == SIGSEGV) {
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*Result = AppSigAct.handler;
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AppSigAct.sigaction = (decltype(AppSigAct.sigaction))Handler;
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return false; // Skip real call.
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}
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return true;
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}
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bool processWorkingSetSigaction(int SigNum, const void *ActVoid,
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void *OldActVoid) {
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VPrintf(2, "%s: %d\n", __FUNCTION__, SigNum);
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if (SigNum == SIGSEGV) {
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const struct sigaction *Act = (const struct sigaction *) ActVoid;
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struct sigaction *OldAct = (struct sigaction *) OldActVoid;
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if (OldAct)
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internal_memcpy(OldAct, &AppSigAct, sizeof(OldAct));
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if (Act)
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internal_memcpy(&AppSigAct, Act, sizeof(AppSigAct));
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return false; // Skip real call.
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}
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return true;
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}
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bool processWorkingSetSigprocmask(int How, void *Set, void *OldSet) {
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VPrintf(2, "%s\n", __FUNCTION__);
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// All we need to do is ensure that SIGSEGV is not blocked.
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// FIXME: we are not fully transparent as we do not pretend that
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// SIGSEGV is still blocked on app queries: that would require
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// per-thread mask tracking.
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if (Set && (How == SIG_BLOCK || How == SIG_SETMASK)) {
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if (internal_sigismember((__sanitizer_sigset_t *)Set, SIGSEGV)) {
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VPrintf(1, "%s: removing SIGSEGV from the blocked set\n", __FUNCTION__);
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internal_sigdelset((__sanitizer_sigset_t *)Set, SIGSEGV);
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}
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}
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return true;
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}
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static void reinstateDefaultHandler(int SigNum) {
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__sanitizer_sigaction SigAct;
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internal_memset(&SigAct, 0, sizeof(SigAct));
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SigAct.sigaction = (decltype(SigAct.sigaction))SIG_DFL;
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int Res = internal_sigaction(SigNum, &SigAct, nullptr);
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CHECK(Res == 0);
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VPrintf(1, "Unregistered for %d handler\n", SigNum);
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}
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// If this is a shadow fault, we handle it here; otherwise, we pass it to the
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// app to handle it just as the app would do without our tool in place.
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static void handleMemoryFault(int SigNum, __sanitizer_siginfo *Info,
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void *Ctx) {
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if (SigNum == SIGSEGV) {
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// We rely on si_addr being filled in (thus we do not support old kernels).
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siginfo_t *SigInfo = (siginfo_t *)Info;
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uptr Addr = (uptr)SigInfo->si_addr;
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if (isShadowMem(Addr)) {
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VPrintf(3, "Shadow fault @%p\n", Addr);
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uptr PageSize = GetPageSizeCached();
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int Res = internal_mprotect((void *)RoundDownTo(Addr, PageSize),
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PageSize, PROT_READ|PROT_WRITE);
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CHECK(Res == 0);
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} else if (AppSigAct.sigaction) {
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// FIXME: For simplicity we ignore app options including its signal stack
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// (we just use ours) and all the delivery flags.
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AppSigAct.sigaction(SigNum, Info, Ctx);
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} else {
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// Crash instead of spinning with infinite faults.
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reinstateDefaultHandler(SigNum);
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}
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} else
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UNREACHABLE("signal not registered");
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}
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void registerMemoryFaultHandler() {
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// We do not use an alternate signal stack, as doing so would require
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// setting it up for each app thread.
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// FIXME: This could result in problems with emulating the app's signal
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// handling if the app relies on an alternate stack for SIGSEGV.
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// We require that SIGSEGV is not blocked. We use a sigprocmask
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// interceptor to ensure that in the future. Here we ensure it for
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// the current thread. We assume there are no other threads at this
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// point during initialization, or that at least they do not block
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// SIGSEGV.
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__sanitizer_sigset_t SigSet;
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internal_sigemptyset(&SigSet);
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internal_sigprocmask(SIG_BLOCK, &SigSet, nullptr);
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__sanitizer_sigaction SigAct;
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internal_memset(&SigAct, 0, sizeof(SigAct));
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SigAct.sigaction = handleMemoryFault;
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// We want to handle nested signals b/c we need to handle a
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// shadow fault in an app signal handler.
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SigAct.sa_flags = SA_SIGINFO | SA_NODEFER;
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int Res = internal_sigaction(SIGSEGV, &SigAct, &AppSigAct);
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CHECK(Res == 0);
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VPrintf(1, "Registered for SIGSEGV handler\n");
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}
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} // namespace __esan
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