[SOLVED] How to fmt.Println() memory not allocated by the go program?

How to fmt.Println() memory not allocated by the go program?

I’d like to print the virtual memory content of the current program from 0x10000 to 0x50000 (an area containing a syscall trampoline on my system).

package main

import (
    "syscall"
    "unsafe"
)
func main() {
    syscall.Syscall(SYS_WRITE, uintptr(1), uintptr(unsafe.Pointer(0x10000)), uintptr(0x40000))
}

However when I tried to compile I’m getting that error :

cannot convert 65536 (type int) to type unsafe.Pointer

In my case,cgo is disabled (import "C" fails at compile time).
Also does syscall.Syscall(SYS_WRITE is the only way to do it ?

Solution

You can convert that address to a slice of bytes, which can then be passed to any Write method.

To convert the address 0x10000 to a slice of bytes with a length of 0x30000, you would use

mem := (*[1 << 30]byte)(unsafe.Pointer(uintptr(0x10000)))[:0x30000:0x30000]

If the size is always static, you could just set the array to the proper size to start

mem := (*[0x30000]byte)(unsafe.Pointer(uintptr(0x10000)))[:]