re PR go/81393 (Bootstrap failure on s390x-linux while building libgo against recent glibc)

	PR go/81393
    syscall: don't use GETREGS/SETREGS on s390
    
    They were removed in recent glibc.
    
    Patch by Andreas Krebbel for GCC PR 81393.
    
    Reviewed-on: https://go-review.googlesource.com/48231

From-SVN: r250174

gcc/go/gofrontend/MERGE

-12c65e8310956eb3cc412d9dc9f9e88cbd928c8e
+9294e79fced202ade7eb236bbe78b766e7e0374f
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/syscall/syscall_linux_s390.go

@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// See the s390x version for why we don't use GETREGSET/SETREGSET
+
 package syscall
 
 import "unsafe"
@@ -12,10 +14,20 @@ func (r *PtraceRegs) PC() uint64 { return uint64(r.Psw.addr) }
 
 func (r *PtraceRegs) SetPC(pc uint64) { r.Psw.addr = uint32(pc) }
 
-func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
-	return ptrace(PTRACE_GETREGS, pid, 0, uintptr(unsafe.Pointer(regsout)))
+func PtraceGetRegs(pid int, regs *PtraceRegs) (err error) {
+	parea := _ptrace_area{
+		_sizeof_ptrace_area,
+		0,
+		uint32(uintptr(unsafe.Pointer(regs))),
+	}
+	return ptrace(PTRACE_PEEKUSR_AREA, pid, uintptr(unsafe.Pointer(&parea)), 0)
 }
 
 func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
-	return ptrace(PTRACE_SETREGS, pid, 0, uintptr(unsafe.Pointer(regs)))
+	parea := _ptrace_area{
+		_sizeof_ptrace_area,
+		0,
+		uint32(uintptr(unsafe.Pointer(regs))),
+	}
+	return ptrace(PTRACE_POKEUSR_AREA, pid, uintptr(unsafe.Pointer(&parea)), 0)
 }

libgo/go/syscall/syscall_linux_s390x.go

@@ -4,6 +4,23 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// The PtraceRegs struct generated for go looks like this:
+//
+// type PtraceRegs struct
+// {
+//   Psw _psw_t;
+//   Gprs [15+1]uint64;
+//   Acrs [15+1]uint32;
+//   Orig_gpr2 uint64;
+//   Fp_regs _s390_fp_regs;
+//   Per_info _per_struct;
+//   Ieee_instruction_pointer uint64;
+// }
+//
+// The GETREGSET/SETREGSET ptrace commands on S/390 only read/write
+// the content up to Orig_gpr2.  Hence, we use
+// PEEKUSR_AREA/POKEUSR_AREA like GDB does.
+
 package syscall
 
 import "unsafe"
@@ -12,10 +29,20 @@ func (r *PtraceRegs) PC() uint64 { return r.Psw.addr }
 
 func (r *PtraceRegs) SetPC(pc uint64) { r.Psw.addr = pc }
 
-func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
-	return ptrace(PTRACE_GETREGS, pid, 0, uintptr(unsafe.Pointer(regsout)))
+func PtraceGetRegs(pid int, regs *PtraceRegs) (err error) {
+	parea := _ptrace_area{
+		_sizeof_ptrace_area,
+		0,
+		uint64(uintptr(unsafe.Pointer(regs))),
+	}
+	return ptrace(PTRACE_PEEKUSR_AREA, pid, uintptr(unsafe.Pointer(&parea)), 0)
 }
 
 func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
-	return ptrace(PTRACE_SETREGS, pid, 0, uintptr(unsafe.Pointer(regs)))
+	parea := _ptrace_area{
+		_sizeof_ptrace_area,
+		0,
+		uint64(uintptr(unsafe.Pointer(regs))),
+	}
+	return ptrace(PTRACE_POKEUSR_AREA, pid, uintptr(unsafe.Pointer(&parea)), 0)
 }