Index: sandbox/linux/services/syscall_wrappers.cc |
diff --git a/sandbox/linux/services/syscall_wrappers.cc b/sandbox/linux/services/syscall_wrappers.cc |
index efadbaf58ea20314fcef6692d40086337db6ce40..1840c96359c37c876c7fd9a8eaec226393b551c7 100644 |
--- a/sandbox/linux/services/syscall_wrappers.cc |
+++ b/sandbox/linux/services/syscall_wrappers.cc |
@@ -29,11 +29,9 @@ |
return syscall(__NR_gettid); |
} |
-long sys_clone(unsigned long flags, |
- decltype(nullptr) child_stack, |
- pid_t* ptid, |
- pid_t* ctid, |
- decltype(nullptr) tls) { |
+namespace { |
+ |
+bool CloneArgumentsValid(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; |
@@ -41,7 +39,65 @@ |
// 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) { |
+ |
+ return !(clone_tls_used || invalid_ctid || invalid_ptid || clone_vm_used); |
+} |
+ |
+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 |
+ |
+long sys_clone(unsigned long flags, |
+ decltype(nullptr) child_stack, |
+ pid_t* ptid, |
+ pid_t* ctid, |
+ decltype(nullptr) tls) { |
+ |
+ if (!CloneArgumentsValid(flags, ptid, ctid)) { |
RAW_LOG(FATAL, "Invalid usage of sys_clone"); |
} |
@@ -58,6 +114,27 @@ |
long sys_clone(unsigned long flags) { |
return sys_clone(flags, nullptr, nullptr, nullptr, nullptr); |
+} |
+ |
+pid_t ForkWithFlags(unsigned long flags, pid_t* ptid, pid_t* ctid) { |
+ if (!CloneArgumentsValid(flags, ptid, ctid)) { |
+ 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()) { |
+ return sys_clone(flags, nullptr, ptid, ctid, nullptr); |
+ } |
+ |
+ jmp_buf env; |
+ if (setjmp(env) == 0) { |
+ return CloneAndLongjmpInChild(flags, ptid, ctid, &env); |
+ } |
+ |
+ return 0; |
} |
void sys_exit_group(int status) { |