1 /*
2  * Copyright (C) 2016 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef _SYSCALL_H_
18 #define _SYSCALL_H_
19 
20 #ifdef __cplusplus
21 extern "C" {
22 #endif
23 
24 #include <stdbool.h>
25 #include <stdint.h>
26 #include <stdarg.h>
27 
28 /*
29  * System calls are indexed by an unsigned 32-bit constant path. To avoid having a
30  * single gigantic table, we use a system of 4-level tables to dispatch them. In
31  * order of use the tables use: 5, 10, 8, 9 bits, from high to low, so for example
32  * syscall 0x19918FC8 would use table indices 3, 200, 199, 456 since it is equal to
33  * (3 << (10 + 8 + 9)) + (200 << (8 + 9)) + (199 << 9) + 456. Each table may be
34  * truncated (with a length field specified), and may be in RAM or ROM, as seen fit.
35  * The expected use case is that the first level detemines grand purpose
36  * (OS, driver, google app, 3rd party app, etc), second level determines vendor,
37  * third level determines subsystem, and the last level determines desired function.
38  */
39 
40 #define SYSCALL_BITS_LEVEL_0      5  /* domain */
41 #define SYSCALL_BITS_LEVEL_1      10 /* family */
42 #define SYSCALL_BITS_LEVEL_2      8  /* genus */
43 #define SYSCALL_BITS_LEVEL_3      9  /* species */
44 
45 #define SYSCALL_CUT_SCALE_SHIFT(_val, _cut, _shift)   ((((uint32_t)(_val)) & ((1UL << (_cut)) - 1)) << (_shift))
46 #define SYSCALL_NO(_domain, _family, _genus, _species) (                                                                                    \
47             SYSCALL_CUT_SCALE_SHIFT((_domain) , SYSCALL_BITS_LEVEL_0, SYSCALL_BITS_LEVEL_1 + SYSCALL_BITS_LEVEL_2 + SYSCALL_BITS_LEVEL_3) + \
48             SYSCALL_CUT_SCALE_SHIFT((_family) , SYSCALL_BITS_LEVEL_1,                        SYSCALL_BITS_LEVEL_2 + SYSCALL_BITS_LEVEL_3) + \
49             SYSCALL_CUT_SCALE_SHIFT((_genus)  , SYSCALL_BITS_LEVEL_2,                                               SYSCALL_BITS_LEVEL_3) + \
50             SYSCALL_CUT_SCALE_SHIFT((_species), SYSCALL_BITS_LEVEL_3,                                                                  0)   \
51                                                        )
52 
53 //level 0 indices:
54 #define SYSCALL_DOMAIN_OS         0
55 #define SYSCALL_DOMAIN_DRIVERS    1 /* hardware drivers for custom hardware */
56 
57 
58 typedef void (*SyscallFunc)(uintptr_t *retValP, va_list args); /* you better know what args you need */
59 
60 struct SyscallTable {
61     uint32_t numEntries;
62     union SyscallTableEntry {
63         struct SyscallTable *subtable;
64         SyscallFunc func;
65     } entry[];
66 };
67 
68 
69 void syscallInit(void);
70 
71 //add a complete table
72 bool syscallAddTable(uint32_t path, uint32_t level, struct SyscallTable *table);
73 
74 //this will only work if the backing table exists...this is intentional to avoid auto growth in scary ways
75 bool syscallAddFunc(uint32_t path, SyscallFunc func);
76 
77 SyscallFunc syscallGetHandler(uint32_t path); // NULL if none
78 
79 
80 #ifdef __cplusplus
81 }
82 #endif
83 
84 #endif
85 
86