Move more helpers to seccomp-bpf-helpers.

sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Note: any code in this file MUST be async-signal safe.
+
+#include "sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h"
+
+#include <unistd.h>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#include "build/build_config.h"
+#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
+
+namespace {
+
+inline bool IsArchitectureX86_64() {
+#if defined(__x86_64__)
+  return true;
+#else
+  return false;
+#endif
+}
+
+// Write |error_message| to stderr. Similar to RawLog(), but a bit more careful
+// about async-signal safety. |size| is the size to write and should typically
+// not include a terminating \0.
+void WriteToStdErr(const char* error_message, size_t size) {
+  while (size > 0) {
+    // TODO(jln): query the current policy to check if send() is available and
+    // use it to perform a non-blocking write.
+    const int ret = HANDLE_EINTR(write(STDERR_FILENO, error_message, size));
+    // We can't handle any type of error here.
+    if (ret <= 0 || static_cast<size_t>(ret) > size) break;
+    size -= ret;
+    error_message += ret;
+  }
+}
+
+// Print a seccomp-bpf failure to handle |sysno| to stderr in an
+// async-signal safe way.
+void PrintSyscallError(uint32_t sysno) {
+  if (sysno >= 1024)
+    sysno = 0;
+  // TODO(markus): replace with async-signal safe snprintf when available.
+  const size_t kNumDigits = 4;
+  char sysno_base10[kNumDigits];
+  uint32_t rem = sysno;
+  uint32_t mod = 0;
+  for (int i = kNumDigits - 1; i >= 0; i--) {
+    mod = rem % 10;
+    rem /= 10;
+    sysno_base10[i] = '0' + mod;
+  }
+  static const char kSeccompErrorPrefix[] =
+      __FILE__":**CRASHING**:seccomp-bpf failure in syscall ";
+  static const char kSeccompErrorPostfix[] = "\n";
+  WriteToStdErr(kSeccompErrorPrefix, sizeof(kSeccompErrorPrefix) - 1);
+  WriteToStdErr(sysno_base10, sizeof(sysno_base10));
+  WriteToStdErr(kSeccompErrorPostfix, sizeof(kSeccompErrorPostfix) - 1);
+}
+
+}  // namespace.
+
+namespace sandbox {
+
+intptr_t CrashSIGSYS_Handler(const struct arch_seccomp_data& args, void* aux) {
+  uint32_t syscall = args.nr;
+  if (syscall >= 1024)
+    syscall = 0;
+  PrintSyscallError(syscall);
+
+  // Encode 8-bits of the 1st two arguments too, so we can discern which socket
+  // type, which fcntl, ... etc., without being likely to hit a mapped
+  // address.
+  // Do not encode more bits here without thinking about increasing the
+  // likelihood of collision with mapped pages.
+  syscall |= ((args.args[0] & 0xffUL) << 12);
+  syscall |= ((args.args[1] & 0xffUL) << 20);
+  // Purposefully dereference the syscall as an address so it'll show up very
+  // clearly and easily in crash dumps.
+  volatile char* addr = reinterpret_cast<volatile char*>(syscall);
+  *addr = '\0';
+  // In case we hit a mapped address, hit the null page with just the syscall,
+  // for paranoia.
+  syscall &= 0xfffUL;
+  addr = reinterpret_cast<volatile char*>(syscall);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+// TODO(jln): refactor the reporting functions.
+
+intptr_t SIGSYSCloneFailure(const struct arch_seccomp_data& args, void* aux) {
+  // "flags" is the first argument in the kernel's clone().
+  // Mark as volatile to be able to find the value on the stack in a minidump.
+#if !defined(NDEBUG)
+  RAW_LOG(ERROR, __FILE__":**CRASHING**:clone() failure\n");
+#endif
+  volatile uint64_t clone_flags = args.args[0];
+  volatile char* addr;
+  if (IsArchitectureX86_64()) {
+    addr = reinterpret_cast<volatile char*>(clone_flags & 0xFFFFFF);
+    *addr = '\0';
+  }
+  // Hit the NULL page if this fails to fault.
+  addr = reinterpret_cast<volatile char*>(clone_flags & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSPrctlFailure(const struct arch_seccomp_data& args,
+                            void* /* aux */) {
+  // Mark as volatile to be able to find the value on the stack in a minidump.
+#if !defined(NDEBUG)
+  RAW_LOG(ERROR, __FILE__":**CRASHING**:prctl() failure\n");
+#endif
+  volatile uint64_t option = args.args[0];
+  volatile char* addr =
+      reinterpret_cast<volatile char*>(option & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSIoctlFailure(const struct arch_seccomp_data& args,
+                            void* /* aux */) {
+  // Make "request" volatile so that we can see it on the stack in a minidump.
+#if !defined(NDEBUG)
+  RAW_LOG(ERROR, __FILE__":**CRASHING**:ioctl() failure\n");
+#endif
+  volatile uint64_t request = args.args[1];
+  volatile char* addr = reinterpret_cast<volatile char*>(request & 0xFFFF);
+  *addr = '\0';
+  // Hit the NULL page if this fails.
+  addr = reinterpret_cast<volatile char*>(request & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+}  // namespace sandbox.