Revert of Move ForkWithFlags from sandbox/ to base/ and plug it into LaunchProcess.

base/process/process_linux.cc

Index: base/process/process_linux.cc
diff --git a/base/process/process_linux.cc b/base/process/process_linux.cc
index cfa3ed5fd07fe887d4a2be08b85ba6308a810206..59ee288f880135bc66d77f47d88478dd2a2aa993 100644
--- a/base/process/process_linux.cc
+++ b/base/process/process_linux.cc
@@ -5,21 +5,14 @@
 #include "base/process/process.h"
 
 #include <errno.h>
-#include <pthread.h>
-#include <sched.h>
-#include <setjmp.h>
 #include <sys/resource.h>
-#include <sys/syscall.h>
 
-#include "base/compiler_specific.h"
 #include "base/files/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
-#include "base/third_party/valgrind/valgrind.h"
-#include "build/build_config.h"
 
 namespace base {
 
@@ -85,52 +78,6 @@
   bool can_reraise_priority;
 };
 
-bool IsRunningOnValgrind() {
-  return RUNNING_ON_VALGRIND;
-}
-
-// This function runs on the stack specified on the clone call. It uses longjmp
-// to switch back to the original stack so the child can return from sys_clone.
-int CloneHelper(void* arg) {
-  jmp_buf* env_ptr = reinterpret_cast<jmp_buf*>(arg);
-  longjmp(*env_ptr, 1);
-
-  // Should not be reached.
-  RAW_CHECK(false);
-  return 1;
-}
-
-// This function is noinline to ensure that stack_buf is below the stack pointer
-// that is saved when setjmp is called below. This is needed because when
-// compiled with FORTIFY_SOURCE, glibc's longjmp checks that the stack is moved
-// upwards. See crbug.com/442912 for more details.
-#if defined(ADDRESS_SANITIZER)
-// Disable AddressSanitizer instrumentation for this function to make sure
-// |stack_buf| is allocated on thread stack instead of ASan's fake stack.
-// Under ASan longjmp() will attempt to clean up the area between the old and
-// new stack pointers and print a warning that may confuse the user.
-__attribute__((no_sanitize_address))
-#endif
-NOINLINE pid_t CloneAndLongjmpInChild(unsigned long flags,
-                                      pid_t* ptid,
-                                      pid_t* ctid,
-                                      jmp_buf* env) {
-  // We use the libc clone wrapper instead of making the syscall
-  // directly because making the syscall may fail to update the libc's
-  // internal pid cache. The libc interface unfortunately requires
-  // specifying a new stack, so we use setjmp/longjmp to emulate
-  // fork-like behavior.
-  char stack_buf[PTHREAD_STACK_MIN];
-#if defined(ARCH_CPU_X86_FAMILY) || defined(ARCH_CPU_ARM_FAMILY) || \
-    defined(ARCH_CPU_MIPS64_FAMILY) || defined(ARCH_CPU_MIPS_FAMILY)
-  // The stack grows downward.
-  void* stack = stack_buf + sizeof(stack_buf);
-#else
-#error "Unsupported architecture"
-#endif
-  return clone(&CloneHelper, stack, flags, env, ptid, nullptr, ctid);
-}
-
 }  // namespace
 
 // static
@@ -189,43 +136,4 @@
   return result == 0;
 }
 
-pid_t ForkWithFlags(unsigned long flags, pid_t* ptid, pid_t* ctid) {
-  const bool clone_tls_used = flags & CLONE_SETTLS;
-  const bool invalid_ctid =
-      (flags & (CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID)) && !ctid;
-  const bool invalid_ptid = (flags & CLONE_PARENT_SETTID) && !ptid;
-
-  // We do not support CLONE_VM.
-  const bool clone_vm_used = flags & CLONE_VM;
-
-  if (clone_tls_used || invalid_ctid || invalid_ptid || clone_vm_used) {
-    RAW_LOG(FATAL, "Invalid usage of ForkWithFlags");
-  }
-
-  // Valgrind's clone implementation does not support specifiying a child_stack
-  // without CLONE_VM, so we cannot use libc's clone wrapper when running under
-  // Valgrind. As a result, the libc pid cache may be incorrect under Valgrind.
-  // See crbug.com/442817 for more details.
-  if (IsRunningOnValgrind()) {
-    // See kernel/fork.c in Linux. There is different ordering of sys_clone
-    // parameters depending on CONFIG_CLONE_BACKWARDS* configuration options.
-#if defined(ARCH_CPU_X86_64)
-    return syscall(__NR_clone, flags, nullptr, ptid, ctid, nullptr);
-#elif defined(ARCH_CPU_X86) || defined(ARCH_CPU_ARM_FAMILY) || \
-    defined(ARCH_CPU_MIPS_FAMILY) || defined(ARCH_CPU_MIPS64_FAMILY)
-    // CONFIG_CLONE_BACKWARDS defined.
-    return syscall(__NR_clone, flags, nullptr, ptid, nullptr, ctid);
-#else
-#error "Unsupported architecture"
-#endif
-  }
-
-  jmp_buf env;
-  if (setjmp(env) == 0) {
-    return CloneAndLongjmpInChild(flags, ptid, ctid, &env);
-  }
-
-  return 0;
-}
-
 }  // namespace base