Add common write_memory and read_memory NetBSD routines

Instead of sharing the native-only code with all BSDs with slightly
different semantics of the kernels, share the NetBSD-only behavior beteen
the NetBSD native and gdbserver setup.

NetBSD does not differentiate the address space I and D in the
operations (contrary to OpenBSD). NetBSD handles EACCES that integrates
with NetBSD specific PaX MPROTECT error handling.

Add a verbose message in the native client that an operation could be
cancelled due to PaX MPROTECT setup.

gdb/ChangeLog:

       * nat/netbsd-nat.c (write_memory, read_memory): Add.
       * nat/netbsd-nat.h (write_memory, read_memory): Likewise.
       * nbsd-nat.c (nbsd_nat_target::xfer_partial): Update.

gdbserver/ChangeLog:

       * netbsd-low.cc (netbsd_process_target::read_memory)
       (netbsd_process_target::write_memory): Update.

1 files changed, 23 insertions, 0 deletions

diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
index 7a07fbf..46dcfac 100644
--- a/gdb/nbsd-nat.c
+++ b/gdb/nbsd-nat.c
@@ -764,6 +764,29 @@ nbsd_nat_target::xfer_partial (enum target_object object,
 	*xfered_len = len;
 	return TARGET_XFER_OK;
       }
+    case TARGET_OBJECT_MEMORY:
+      {
+	size_t xfered;
+	int res;
+	if (writebuf != nullptr)
+	  res = netbsd_nat::write_memory (pid, writebuf, offset, len, &xfered);
+	else
+	  res = netbsd_nat::read_memory (pid, readbuf, offset, len, &xfered);
+	if (res != 0)
+	  {
+	    if (res == EACCES)
+	      fprintf_unfiltered (gdb_stderr, "Cannot %s process at %s (%s). "
+				  "Is PaX MPROTECT active? See security(7), "
+				  "sysctl(7), paxctl(8)\n",
+				  (writebuf ? "write to" : "read from"),
+				  pulongest (offset), safe_strerror (errno));
+	    return TARGET_XFER_E_IO;
+	  }
+	if (xfered == 0)
+	  return TARGET_XFER_EOF;
+	*xfered_len = (ULONGEST) xfered;
+	return TARGET_XFER_OK;
+      }
     default:
       return inf_ptrace_target::xfer_partial (object, annex,
 					      readbuf, writebuf, offset,