feat add marl for fiber

3party/marl/src/osfiber_x86.c

@@ -0,0 +1,47 @@
+// Copyright 2019 The Marl Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#if defined(__i386__)
+
+#include "osfiber_asm_x86.h"
+
+#include "marl/export.h"
+
+MARL_EXPORT
+void marl_fiber_trampoline(void (*target)(void*), void* arg) {
+  target(arg);
+}
+
+MARL_EXPORT
+void marl_fiber_set_target(struct marl_fiber_context* ctx,
+                           void* stack,
+                           uint32_t stack_size,
+                           void (*target)(void*),
+                           void* arg) {
+  // The stack pointer needs to be 16-byte aligned when making a 'call'.
+  // The 'call' instruction automatically pushes the return instruction to the
+  // stack (4-bytes), before making the jump.
+  // The marl_fiber_swap() assembly function does not use 'call', instead it
+  // uses 'jmp', so we need to offset the ESP pointer by 4 bytes so that the
+  // stack is still 16-byte aligned when the return target is stack-popped by
+  // the callee.
+  uintptr_t* stack_top = (uintptr_t*)((uint8_t*)(stack) + stack_size);
+  ctx->EIP = (uintptr_t)&marl_fiber_trampoline;
+  ctx->ESP = (uintptr_t)&stack_top[-5];
+  stack_top[-3] = (uintptr_t)arg;
+  stack_top[-4] = (uintptr_t)target;
+  stack_top[-5] = 0;  // No return target.
+}
+
+#endif  // defined(__i386__)