blob: cac72cb94f37c58227b924b56ba14aedc3994ba0 [file] [log] [blame]
// 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"
void marl_fiber_trampoline(void (*target)(void*), void* arg) {
target(arg);
}
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__)