Chromium Code Reviews
chromiumcodereview-hr@appspot.gserviceaccount.com (chromiumcodereview-hr) | Please choose your nickname with Settings | Help | Chromium Project | Gerrit Changes | Sign out
(989)

Unified Diff: src/trap-handler/handler-inside.cc

Issue 2723133003: Revert of [wasm] Initial signal handler (Closed)
Patch Set: Created 3 years, 10 months ago
Use n/p to move between diff chunks; N/P to move between comments. Draft comments are only viewable by you.
Jump to:
View side-by-side diff with in-line comments
Download patch
« no previous file with comments | « src/trap-handler/OWNERS ('k') | src/trap-handler/handler-outside.cc » ('j') | no next file with comments »
Expand Comments ('e') | Collapse Comments ('c') | Show Comments Hide Comments ('s')
Index: src/trap-handler/handler-inside.cc
diff --git a/src/trap-handler/handler-inside.cc b/src/trap-handler/handler-inside.cc
deleted file mode 100644
index a51bd9427f0c9585e0f21cc4cc46a6736416750e..0000000000000000000000000000000000000000
--- a/src/trap-handler/handler-inside.cc
+++ /dev/null
@@ -1,170 +0,0 @@
-// Copyright 2017 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// PLEASE READ BEFORE CHANGING THIS FILE!
-//
-// This file implements the out of bounds signal handler for
-// WebAssembly. Signal handlers are notoriously difficult to get
-// right, and getting it wrong can lead to security
-// vulnerabilities. In order to minimize this risk, here are some
-// rules to follow.
-//
-// 1. Do not introduce any new external dependencies. This file needs
-// to be self contained so it is easy to audit everything that a
-// signal handler might do.
-//
-// 2. Any changes must be reviewed by someone from the crash reporting
-// or security team. See OWNERS for suggested reviewers.
-//
-// For more information, see https://goo.gl/yMeyUY.
-//
-// This file contains most of the code that actually runs in a signal handler
-// context. Some additional code is used both inside and outside the signal
-// handler. This code can be found in handler-shared.cc.
-
-#include <signal.h>
-#include <stddef.h>
-#include <stdlib.h>
-
-#include "src/trap-handler/trap-handler-internal.h"
-#include "src/trap-handler/trap-handler.h"
-
-namespace v8 {
-namespace internal {
-namespace trap_handler {
-
-namespace {
-
-bool IsKernelGeneratedSignal(siginfo_t* info) {
- return info->si_code > 0 && info->si_code != SI_USER &&
- info->si_code != SI_QUEUE && info->si_code != SI_TIMER &&
- info->si_code != SI_ASYNCIO && info->si_code != SI_MESGQ;
-}
-
-#if V8_TRAP_HANDLER_SUPPORTED
-class SigUnmaskStack {
- public:
- explicit SigUnmaskStack(sigset_t sigs) {
- // TODO(eholk): consider using linux-syscall-support for calling this
- // syscall.
- pthread_sigmask(SIG_UNBLOCK, &sigs, &old_mask_);
- }
-
- ~SigUnmaskStack() { pthread_sigmask(SIG_SETMASK, &old_mask_, nullptr); }
-
- private:
- sigset_t old_mask_;
-
- // We'd normally use DISALLOW_COPY_AND_ASSIGN, but we're avoiding a dependency
- // on base/macros.h
- SigUnmaskStack(const SigUnmaskStack&) = delete;
- void operator=(const SigUnmaskStack&) = delete;
-};
-#endif
-} // namespace
-
-#if V8_TRAP_HANDLER_SUPPORTED && V8_OS_LINUX
-bool TryHandleSignal(int signum, siginfo_t* info, ucontext_t* context) {
- // Bail out early in case we got called for the wrong kind of signal.
- if (signum != SIGSEGV) {
- return false;
- }
-
- // Make sure the signal was generated by the kernel and not some other source.
- if (!IsKernelGeneratedSignal(info)) {
- return false;
- }
-
- // Ensure the faulting thread was actually running Wasm code.
- if (!IsThreadInWasm()) {
- return false;
- }
-
- // Clear g_thread_in_wasm_code, primarily to protect against nested faults.
- g_thread_in_wasm_code = false;
-
- // Begin signal mask scope. We need to be sure to restore the signal mask
- // before we restore the g_thread_in_wasm_code flag.
- {
- // Unmask the signal so that if this signal handler crashes, the crash will
- // be handled by the crash reporter. Otherwise, the process might be killed
- // with the crash going unreported.
- sigset_t sigs;
- // Fortunately, sigemptyset and sigaddset are async-signal-safe according to
- // the POSIX standard.
- sigemptyset(&sigs);
- sigaddset(&sigs, SIGSEGV);
- SigUnmaskStack unmask(sigs);
-
- uintptr_t fault_addr = context->uc_mcontext.gregs[REG_RIP];
-
- // TODO(eholk): broad code range check
-
- // Taking locks in a signal handler is risky because a fault in the signal
- // handler could lead to a deadlock when attempting to acquire the lock
- // again. We guard against this case with g_thread_in_wasm_code. The lock
- // may only be taken when not executing Wasm code (an assert in
- // MetadataLock's constructor ensures this). This signal handler will bail
- // out before trying to take the lock if g_thread_in_wasm_code is not set.
- MetadataLock lock_holder;
-
- for (size_t i = 0; i < gNumCodeObjects; ++i) {
- const CodeProtectionInfo* data = gCodeObjects[i].code_info;
- if (data == nullptr) {
- continue;
- }
- const uintptr_t base = reinterpret_cast<uintptr_t>(data->base);
-
- if (fault_addr >= base && fault_addr < base + data->size) {
- // Hurray, we found the code object. Check for protected addresses.
- const ptrdiff_t offset = fault_addr - base;
-
- for (unsigned i = 0; i < data->num_protected_instructions; ++i) {
- if (data->instructions[i].instr_offset == offset) {
- // Hurray again, we found the actual instruction. Tell the caller to
- // return to the landing pad.
- context->uc_mcontext.gregs[REG_RIP] =
- data->instructions[i].landing_offset + base;
- return true;
- }
- }
- }
- }
- } // end signal mask scope
-
- // If we get here, it's not a recoverable wasm fault, so we go to the next
- // handler.
- g_thread_in_wasm_code = true;
- return false;
-}
-#endif // V8_TRAP_HANDLER_SUPPORTED && V8_OS_LINUX
-
-#if V8_TRAP_HANDLER_SUPPORTED
-void HandleSignal(int signum, siginfo_t* info, void* context) {
- ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
-
- if (!TryHandleSignal(signum, info, uc)) {
- // Since V8 didn't handle this signal, we want to re-raise the same signal.
- // For kernel-generated SEGV signals, we do this by restoring the default
- // SEGV handler and then returning. The fault will happen again and the
- // usual SEGV handling will happen.
- //
- // We handle user-generated signals by calling raise() instead. This is for
- // completeness. We should never actually see one of these, but just in
- // case, we do the right thing.
- struct sigaction action;
- action.sa_handler = SIG_DFL;
- sigemptyset(&action.sa_mask);
- action.sa_flags = 0;
- sigaction(signum, &action, nullptr);
- if (!IsKernelGeneratedSignal(info)) {
- raise(signum);
- }
- }
- // TryHandleSignal modifies context to change where we return to.
-}
-#endif
-} // namespace trap_handler
-} // namespace internal
-} // namespace v8
« no previous file with comments | « src/trap-handler/OWNERS ('k') | src/trap-handler/handler-outside.cc » ('j') | no next file with comments »

Powered by Google App Engine
This is Rietveld 408576698