When running the following code:
__gshared void* return_ptr;
__gshared void* injected_fn = &fn;
void main() {
buffer(7);
printf("End main\n");
}
void buffer() {
test(x);
printf("End buffer\n");
}
void test() {
printf("This is a test!\n");
inject();
printf("End of the test!\n");
}
void fn() {
printf("Hello, world!\n");
asm {
mov RAX, return_ptr;
mov [RBP+8], RAX;
}
}
void inject() {
asm {
naked;
push RAX;
mov RAX, [RBP+8];
mov return_ptr, RAX;
mov RAX, injected_fn;
mov [RBP+8], RAX;
pop RAX;
ret;
}
}
The program behaves as expected, that is, the program prints
This is a test!
End of the test!
Hello, world!
End buffer
End main
However, if I call test directly from main, it results in a
segfault.
If I call inject directly from main, it works.
And, oddly, if I add any amount of inline assembler to main, and
call test there, it works.
Could anyone explain to me what's going on?
