syscall: add ptracePtr that accepts pointer arg as unsafe.Pointer

The existing ptrace wrapper accepts pointer argument as an uintptr which
often points to the memory allocated in Go. This violates unsafe.Pointer safety
rules.

Fixes #58387

Change-Id: Iab12122c495953f94ea00c2a61654a818a464205
Reviewed-on: https://go-review.googlesource.com/c/go/+/470299
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Dmitri Goutnik <dgoutnik@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Dmitri Goutnik <dgoutnik@gmail.com>

1 files changed, 8 insertions, 7 deletions

diff --git a/src/syscall/syscall_linux.go b/src/syscall/syscall_linux.go
index f337388a74..c1f43bf43d 100644
--- a/src/syscall/syscall_linux.go
+++ b/src/syscall/syscall_linux.go
@@ -828,6 +828,7 @@ func BindToDevice(fd int, device string) (err error) {
 }
 
 //sys	ptrace(request int, pid int, addr uintptr, data uintptr) (err error)
+//sys	ptracePtr(request int, pid int, addr uintptr, data unsafe.Pointer) (err error) = SYS_PTRACE
 
 func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err error) {
 	// The peek requests are machine-size oriented, so we wrap it
@@ -845,7 +846,7 @@ func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err erro
 	// boundary.
 	n := 0
 	if addr%sizeofPtr != 0 {
-		err = ptrace(req, pid, addr-addr%sizeofPtr, uintptr(unsafe.Pointer(&buf[0])))
+		err = ptracePtr(req, pid, addr-addr%sizeofPtr, unsafe.Pointer(&buf[0]))
 		if err != nil {
 			return 0, err
 		}
@@ -857,7 +858,7 @@ func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err erro
 	for len(out) > 0 {
 		// We use an internal buffer to guarantee alignment.
 		// It's not documented if this is necessary, but we're paranoid.
-		err = ptrace(req, pid, addr+uintptr(n), uintptr(unsafe.Pointer(&buf[0])))
+		err = ptracePtr(req, pid, addr+uintptr(n), unsafe.Pointer(&buf[0]))
 		if err != nil {
 			return n, err
 		}
@@ -885,7 +886,7 @@ func ptracePoke(pokeReq int, peekReq int, pid int, addr uintptr, data []byte) (c
 	n := 0
 	if addr%sizeofPtr != 0 {
 		var buf [sizeofPtr]byte
-		err = ptrace(peekReq, pid, addr-addr%sizeofPtr, uintptr(unsafe.Pointer(&buf[0])))
+		err = ptracePtr(peekReq, pid, addr-addr%sizeofPtr, unsafe.Pointer(&buf[0]))
 		if err != nil {
 			return 0, err
 		}
@@ -912,7 +913,7 @@ func ptracePoke(pokeReq int, peekReq int, pid int, addr uintptr, data []byte) (c
 	// Trailing edge.
 	if len(data) > 0 {
 		var buf [sizeofPtr]byte
-		err = ptrace(peekReq, pid, addr+uintptr(n), uintptr(unsafe.Pointer(&buf[0])))
+		err = ptracePtr(peekReq, pid, addr+uintptr(n), unsafe.Pointer(&buf[0]))
 		if err != nil {
 			return n, err
 		}
@@ -937,11 +938,11 @@ func PtracePokeData(pid int, addr uintptr, data []byte) (count int, err error) {
 }
 
 func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
-	return ptrace(PTRACE_GETREGS, pid, 0, uintptr(unsafe.Pointer(regsout)))
+	return ptracePtr(PTRACE_GETREGS, pid, 0, unsafe.Pointer(regsout))
 }
 
 func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
-	return ptrace(PTRACE_SETREGS, pid, 0, uintptr(unsafe.Pointer(regs)))
+	return ptracePtr(PTRACE_SETREGS, pid, 0, unsafe.Pointer(regs))
 }
 
 func PtraceSetOptions(pid int, options int) (err error) {
@@ -950,7 +951,7 @@ func PtraceSetOptions(pid int, options int) (err error) {
 
 func PtraceGetEventMsg(pid int) (msg uint, err error) {
 	var data _C_long
-	err = ptrace(PTRACE_GETEVENTMSG, pid, 0, uintptr(unsafe.Pointer(&data)))
+	err = ptracePtr(PTRACE_GETEVENTMSG, pid, 0, unsafe.Pointer(&data))
 	msg = uint(data)
 	return
 }