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#include "substitute.h"
#include <unistd.h>
#include <stdio.h>
#include <mach-o/dyld.h>
#include <assert.h>
static void *getpid_plus = (void *) getpid + 5;
static pid_t (*old_getpid)();
static pid_t my_getpid() {
return old_getpid() + 1;
}
static gid_t my_getgid() {
return 42;
}
int main() {
const char *self = _dyld_get_image_name(0);
void *handle = substitute_open_image(self);
assert(handle);
struct substitute_import_hook hooks[] = {
{"_getpid", my_getpid, &old_getpid},
{"_getgid", my_getgid, NULL},
};
pid_t (*gp)() = getpid_plus - 5;
printf("original pid: %d\n", (int) gp());
substitute_interpose_imports(handle, hooks, sizeof(hooks)/sizeof(*hooks), 0);
gp = getpid_plus - 5;
printf("new pid: %d\n", (int) gp());
printf("new gid: %d\n", (int) getgid());
substitute_close_image(handle);
}
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