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
|
// macos-fix-jit - Fix Ares JIT support on macOS with old linkers
//
// Ares JIT requires the data segment to be executable (see
// https://github.com/ares-emulator/ares/pull/200 for details on why
// this is done instead of allocating a new segment via mmap).
//
// To do this, it uses mprotect() (bump_allocator::resize), but it also
// needs to tell the linker that the data segment can be upgraded to executable
// with -Wl,-segprot,__DATA,rwx,rw (nall/GNUmakefile). Unfortunately, for quite
// some time, the clang LD had a bug and didn't accept that option for the
// data segment. The bug was fixed in Xcode 11.4.1.
//
// The official CI has a newer linker without the bug, but for developers compiling
// ares with an old toolchain, this small tool will patch the binary to
// mark the data segment as potentially executable.
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#define VM_PROT_R 1
#define VM_PROT_W 2
#define VM_PROT_X 4
bool is_64bit = false;
bool is_le = false;
uint32_t read32(FILE *f) {
if (is_le) {
uint32_t x = fgetc(f);
x |= fgetc(f) << 8;
x |= fgetc(f) << 16;
x |= fgetc(f) << 24;
return x;
} else {
uint32_t x = fgetc(f) << 24;
x |= fgetc(f) << 16;
x |= fgetc(f) << 8;
x |= fgetc(f);
return x;
}
}
void write32(FILE *f, uint32_t x) {
if (is_le) {
fputc(x, f); fputc(x>>8, f); fputc(x>>16, f); fputc(x>>24, f);
} else {
fputc(x>>24, f); fputc(x>>16, f); fputc(x>>8, f); fputc(x, f);
}
}
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "Usage: %s <ares-binary>\n", argv[0]);
return 1;
}
FILE *f = fopen(argv[1], "r+w");
if (!f) {
fprintf(stderr, "cannot open file: %s\n", argv[1]);
return 1;
}
uint32_t magic = read32(f);
switch (magic) {
case 4277009102: is_64bit = false; is_le = false; break;
case 4277009103: is_64bit = true; is_le = false; break;
case 3472551422: is_64bit = false; is_le = true; break;
case 3489328638: is_64bit = true; is_le = true; break;
case 3405691582: fprintf(stderr, "universal binary is not supported"); return 1;
default: fprintf(stderr, "invalid MachO magic number: %u\n", magic); return 1;
}
fseek(f, 3*4, SEEK_CUR);
uint32_t nlcs = read32(f);
fseek(f, (2+is_64bit)*4, SEEK_CUR);
if (nlcs > 1024) {
fprintf(stderr, "too many MachO load commands, header corrupted? (%08x)", nlcs);
return 1;
}
for (int i=0; i<nlcs; i++) {
uint32_t cmd = read32(f);
uint32_t sz = read32(f);
int next = ftell(f) + sz - 8;
// Search for the command LC_SEGMENT_64 on data segment
if (cmd == 0x19) {
char segname[17] = {0};
fread(segname, 1, 16, f);
if (!strcmp(segname, "__DATA")) {
fseek(f, 4*(1+is_64bit)*4, SEEK_CUR);
uint32_t maxprot = read32(f);
switch (maxprot) {
case VM_PROT_R | VM_PROT_W | VM_PROT_X:
return 0; // binary already patched, nothing to do
case VM_PROT_R | VM_PROT_W:
// Tell the kernel that the binary can upgrade __DATA to +x
maxprot |= VM_PROT_X;
fseek(f, -4, SEEK_CUR);
write32(f, maxprot);
fclose(f);
return 0;
default:
fprintf(stderr, "unexpected maxprot for __DATA segment: %x\n", maxprot);
return 1;
}
}
}
fseek(f, next, SEEK_SET);
}
fprintf(stderr, "cannot find LC_SEGMENT_64 for __DATA segment\n");
return 0;
}
|
