Hi, this is the smallest example I can think of but I have know idea how I
am suppose to do the syscall and trampoline part?
./c/hello.c
---------
#include <stdio.h>
#include <string.h>
int hello(char *s) {
char c[80];
strcpy (c, s);
sprintf(s, "hello %s", c);
return 0;
}
clang -shared -fpic hello.c -o hello.dylib
./trampoline.s
-----------------
#include "textflag.h"
TEXT ·hello_trampoline(SB),NOSPLIT,$0-0
JMP hello(SB)
./main.go
-----------
package main
import "unsafe"
//go:linkname hello_c hello_c
//go:cgo_import_dynamic hello_c hello "./c/hello.dylib"
func hello_c(s unsafe.Pointer) uintptr {
return syscall(funcPC(hello_trampoline), uintptr(s), uintptr(0), 0, 0,
uintptr(s), 0)
}
func hello_trampoline()
func syscall(fn, a1, a2, a3, a4, a5, a6 uintptr) uintptr
//go:nosplit
func funcPC(f func()) uintptr {
return **(**uintptr)(unsafe.Pointer(&f))
}
func main() {
s := "test"
hello_c(unsafe.Pointer(&s))
print(s)
}
(go version devel +98d20fb235 Fri May 8 02:31:13 2020 +0000 darwin/amd64)
main.main: relocation target main.syscall not defined
main.hello_trampoline: relocation target hello not defined
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