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1/*
2 * Copyright (c) 2023-2025 Huawei Device Co., Ltd.
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 * http://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
16#include "runtime/fibers/arch/asm_macros.h"
17#include "runtime/fibers/arch/arm/context_layout.h"
18
19.extern abort
20
21LOCAL_FUNCTION_START(FiberExitBridge)
22    // indicate abnormal exit by calling exit(-1)
23    // because fibers should not return from FiberProc
24    // mov r0, #-1
25    // bl exit
26
27    // let's make the exit more violent than exit(-1) for now
28    // TODO(konstanting, #IAD5MH): revert to exit() when everything is tested and works
29    bl abort
30FUNCTION_END(FiberExitBridge)
31
32#define GPR_O(reg) FCTX_GPR_OFFSET_BYTES_ ## reg
33#define FP_O(reg) FCTX_FP_OFFSET_BYTES_ ## reg
34
35/**
36 * arguments:
37 * r0: uint8_t* ctx_memory
38 * r1: void (*func)(void*)
39 * r2: void* argument
40 * r3: uint8_t* stack
41 * [sp]: size_t stack_size_bytes
42 */
43FUNCTION_START(UpdateContext)
44    // context->PC = func
45    str r1, [r0, # GPR_O(PC)]
46    // now we can reuse r1
47    // context->LR = FiberExitBridge (for the case when Fiber returns)
48    adr r1, FiberExitBridge
49    str r1, [r0, # GPR_O(LR)]
50    // context->R0 = argument
51    str r2, [r0, # GPR_O(R0)]
52
53    /**
54     * r1 will hold the new SP value:
55     * NEW_SP = align((stack + stack_size), 16B)
56     */
57
58    // r1 = stack + stack_size_bytes
59    ldr r1, [sp]
60    add r1, r3, r1
61    // r1 = align(r1, 16B)
62    and r1, r1, #-16
63    // context->SP = r1
64    str r1, [r0, # GPR_O(SP)]
65    // context->FP = 0
66    mov r1, #0
67    str r1, [r0, # GPR_O(R11)]
68
69    // return success
70    mov r0, #0
71    blx lr
72FUNCTION_END(UpdateContext)
73
74/**
75 * arguments:
76 * r0: uint8_t* ctx_memory
77 * r1: void (*func)(void*)
78 * r2: void* argument
79 */
80FUNCTION_START(UpdateContextKeepStack)
81    // r4 = context->PC
82    ldr r4, [r0, # GPR_O(PC)]
83    // context->PC = func
84    str r1, [r0, # GPR_O(PC)]
85    // context->R0 = argument
86    str r2, [r0, # GPR_O(R0)]
87
88    // pretend that we called the func(), i.e. put context's PC to LR
89    // context->LR = r4
90    str r4, [r0, # GPR_O(LR)]
91
92    // return success
93    mov r0, #0
94    blx lr
95FUNCTION_END(UpdateContextKeepStack)
96
97#undef GPR_O
98#undef FP_O
99
100// we don't need executable stack.
101.section .note.GNU-stack,"",%progbits