1
/*
2
 * For each rebinding in rebindings, rebinds references to external, indirect
3
 * symbols with the specified name to instead point at replacement for each
4
 * image in the calling process as well as for all future images that are loaded
5
 * by the process. If rebind_functions is called more than once, the symbols to
6
 * rebind are added to the existing list of rebindings, and if a given symbol
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 * is rebound more than once, the later rebinding will take precedence.
8
 */
9
FISHHOOK_VISIBILITY
10
int rebind_symbols(struct rebinding rebindings[], size_t rebindings_nel);

1
/*
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 * A structure representing a particular intended rebinding from a symbol
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 * name to its replacement
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 */
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struct rebinding {
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  const char *name;
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  void *replacement;
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  void **replaced;
9
};

1
- (void)viewDidLoad {
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    [super viewDidLoad];
3
    self.view.backgroundColor = [UIColor blackColor];
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    // 目标去Hook系统的NSLog函数
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6
    struct rebinding nslog;
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    nslog.name = "NSLog";
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    nslog.replacement = hook_NSLog;
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    // 保存NSLog函数的指针
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    nslog.replaced = (void *)&sys_NSLog;
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12
    struct rebinding bds[] = {nslog};
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14
    rebind_symbols(bds, 1);
15
}
16

17
/// 旧函数的指针
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static void (*sys_NSLog)(NSString *format, ...);
19

20
// 新函数
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void hook_NSLog(NSString *format, ...) {
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    format = [format stringByAppendingString:@"\n🌈"];
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    // 再调用系统的
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    sys_NSLog(format);
25
}
26

27
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
28
    NSLog(@"RyukieLog");
29
}

1
2021-05-05 15:51:44.230666+0800 Hook[1650:239418] RyukieLog
2
🌈
3
2021-05-05 15:51:44.430579+0800 Hook[1650:239418] RyukieLog
4
🌈
5
2021-05-05 15:51:44.679392+0800 Hook[1650:239418] RyukieLog
6
🌈

1
void logFun(const char * str) {
2
    NSLog(@"%s", str);
3
}

1
struct rebinding nslog;
2
nslog.name = "logFun";
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nslog.replacement = new_logfun;
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nslog.replaced = (void *)&old_logfun;
5

6
static void(*old_logfun)(const char * str);
7

8
void new_logfun(const char * str) {
9
    str = "🌈";
10
    // 再调用旧的
11
    old_logfun(str);
12
}