1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
// MIT License, Copyright (c) 2021 Marvin Borner
#include <dev.h>
#include <fs/ext2.h>
#include <lib.h>
#include <pnc.h>
static void ext2_buffer_read(u32 block, void *buf, struct dev *dev)
{
dev->read(buf, block * SECTOR_COUNT, SECTOR_COUNT, dev);
}
static void ext2_get_superblock(struct ext2_superblock *buf, struct dev *dev)
{
u8 data[BLOCK_SIZE] = { 0 };
ext2_buffer_read(EXT2_SUPER, data, dev);
memcpy(buf, data, sizeof(*buf));
assert(buf->magic == EXT2_MAGIC);
}
static struct ext2_inode *ext2_get_inode(u32 i, struct ext2_inode *in_buf, struct dev *dev)
{
struct ext2_superblock sb = { 0 };
ext2_get_superblock(&sb, dev);
u8 data[BLOCK_SIZE] = { 0 };
ext2_buffer_read(EXT2_SUPER + 1, data, dev);
struct ext2_bgd *bgd = (struct ext2_bgd *)data;
u32 block_group = (i - 1) / sb.inodes_per_group;
u32 index = (i - 1) % sb.inodes_per_group;
u32 block = (index * EXT2_INODE_SIZE) / BLOCK_SIZE;
bgd += block_group;
u8 buf[BLOCK_SIZE] = { 0 };
ext2_buffer_read(bgd->inode_table + block, buf, dev);
struct ext2_inode *in =
(struct ext2_inode *)((u32)buf +
(index % (BLOCK_SIZE / EXT2_INODE_SIZE)) * EXT2_INODE_SIZE);
memcpy(in_buf, in, sizeof(*in_buf));
return in_buf;
}
static u32 ext2_read_indirect(u32 indirect, u32 block_num, struct dev *dev)
{
u8 buf[BLOCK_SIZE] = { 0 };
ext2_buffer_read(indirect, buf, dev);
u32 ind = *(u32 *)((u32)buf + block_num * sizeof(u32));
return ind;
}
static s32 ext2_read_inode(struct ext2_inode *in, void *buf, u32 offset, u32 count, struct dev *dev)
{
if (!in || !buf)
return -1;
if (in->size == 0)
return 0;
u32 num_blocks = in->blocks / (BLOCK_SIZE / SECTOR_SIZE) + 1;
if (!num_blocks)
return -1;
u32 first_block = offset / BLOCK_SIZE;
u32 last_block = (offset + count) / BLOCK_SIZE;
if (last_block >= num_blocks)
last_block = num_blocks - 1;
u32 first_block_offset = offset % BLOCK_SIZE;
u32 remaining = MIN(count, in->size - offset);
u32 copied = 0;
u32 indirect, blocknum;
// TODO: Support triply indirect pointers
for (u32 i = first_block; i <= last_block; i++) {
if (i < 12) {
blocknum = in->block[i];
} else if (i < BLOCK_COUNT + 12) {
indirect = in->block[12];
blocknum = ext2_read_indirect(indirect, i - 12, dev);
} else {
indirect = in->block[13];
blocknum = ext2_read_indirect(indirect,
(i - (BLOCK_COUNT + 12)) / BLOCK_COUNT, dev);
blocknum = ext2_read_indirect(blocknum,
(i - (BLOCK_COUNT + 12)) % BLOCK_COUNT, dev);
}
u8 data[BLOCK_SIZE] = { 0 };
ext2_buffer_read(blocknum, data, dev);
u32 block_offset = (i == first_block) ? first_block_offset : 0;
u32 byte_count = MIN(BLOCK_SIZE - block_offset, remaining);
memcpy((u8 *)buf + copied, data + block_offset, byte_count);
copied += byte_count;
remaining -= byte_count;
}
return copied;
}
static u32 ext2_find_inode(const char *name, u32 dir_inode, struct dev *dev)
{
if ((signed)dir_inode <= 0)
return (unsigned)-1;
struct ext2_inode i = { 0 };
ext2_get_inode(dir_inode, &i, dev);
char buf[BLOCK_SIZE] = { 0 };
assert(BLOCK_SIZE * i.blocks / 2 <= sizeof(buf)); // Shouldn't fail
u8 data[BLOCK_SIZE] = { 0 };
for (u32 q = 0; q < i.blocks / 2; q++) {
ext2_buffer_read(i.block[q], data, dev);
memcpy((u32 *)((u32)buf + q * BLOCK_SIZE), data, BLOCK_SIZE);
}
struct ext2_dirent *d = (struct ext2_dirent *)buf;
u32 sum = 0;
do {
// Calculate the 4byte aligned size of each entry
sum += d->total_len;
if (strlen(name) == d->name_len &&
strncmp((void *)d->name, name, d->name_len) == 0) {
return d->inode_num;
}
d = (struct ext2_dirent *)((u32)d + d->total_len);
} while (sum < (1024 * i.blocks / 2));
return (unsigned)-1;
}
static struct ext2_inode *ext2_find_inode_by_path(const char *path, struct ext2_inode *in_buf,
struct dev *dev)
{
char path_arr[1024] = { 0 };
strlcpy(path_arr, path, sizeof(path_arr));
char *path_cp = path_arr;
if (path_cp[0] != '/')
return NULL;
path_cp++;
u32 current_inode = EXT2_ROOT;
while (1) {
u32 i;
for (i = 0; path_cp[i] != '/' && path_cp[i] != '\0'; i++)
;
if (path_cp[i] == '\0')
break;
path_cp[i] = '\0';
current_inode = ext2_find_inode(path_cp, current_inode, dev);
path_cp[i] = '/';
if ((signed)current_inode <= 0) {
return NULL;
}
path_cp += i + 1;
}
u32 inode = ext2_find_inode(path_cp, current_inode, dev);
if ((signed)inode <= 0)
return NULL;
return ext2_get_inode(inode, in_buf, dev);
}
static s32 ext2_read(const char *path, void *buf, u32 offset, u32 count, struct dev *dev)
{
struct ext2_inode in = { 0 };
if (ext2_find_inode_by_path(path, &in, dev) == &in) {
return ext2_read_inode(&in, buf, offset, count, dev);
} else {
return -1;
}
}
u8 ext2_detect(struct dev *dev)
{
struct ext2_superblock sb = { 0 };
ext2_get_superblock(&sb, dev);
if (sb.magic != EXT2_MAGIC)
return 0;
dev->fs.read = ext2_read;
return 1;
}
|
