1 // Copyright 2019 The Marl Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #if defined(__i386__)
16
17 #include "osfiber_asm_x86.h"
18
19 #include "marl/export.h"
20
21 MARL_EXPORT
marl_fiber_trampoline(void (* target)(void *),void * arg)22 void marl_fiber_trampoline(void (*target)(void*), void* arg) {
23 target(arg);
24 }
25
26 MARL_EXPORT
marl_fiber_set_target(struct marl_fiber_context * ctx,void * stack,uint32_t stack_size,void (* target)(void *),void * arg)27 void marl_fiber_set_target(struct marl_fiber_context* ctx,
28 void* stack,
29 uint32_t stack_size,
30 void (*target)(void*),
31 void* arg) {
32 // The stack pointer needs to be 16-byte aligned when making a 'call'.
33 // The 'call' instruction automatically pushes the return instruction to the
34 // stack (4-bytes), before making the jump.
35 // The marl_fiber_swap() assembly function does not use 'call', instead it
36 // uses 'jmp', so we need to offset the ESP pointer by 4 bytes so that the
37 // stack is still 16-byte aligned when the return target is stack-popped by
38 // the callee.
39 uintptr_t* stack_top = (uintptr_t*)((uint8_t*)(stack) + stack_size);
40 ctx->EIP = (uintptr_t)&marl_fiber_trampoline;
41 ctx->ESP = (uintptr_t)&stack_top[-5];
42 stack_top[-3] = (uintptr_t)arg;
43 stack_top[-4] = (uintptr_t)target;
44 stack_top[-5] = 0; // No return target.
45 }
46
47 #endif // defined(__i386__)
48