Add readMemory and writeMemory requests to DAP

This adds the DAP readMemory and writeMemory requests.  A small change
to the evaluation code is needed in order to test this -- this is one
of the few ways for a client to actually acquire a memory reference.

gdb/data-directory/Makefile.in

@@ -96,6 +96,7 @@ PYTHON_FILE_LIST = \
 	gdb/dap/__init__.py \
 	gdb/dap/io.py \
 	gdb/dap/launch.py \
+	gdb/dap/memory.py \
 	gdb/dap/next.py \
 	gdb/dap/pause.py \
 	gdb/dap/scopes.py \

gdb/python/lib/gdb/dap/__init__.py

@@ -25,6 +25,7 @@ from . import bt
 from . import disassemble
 from . import evaluate
 from . import launch
+from . import memory
 from . import next
 from . import pause
 from . import scopes

gdb/python/lib/gdb/dap/memory.py

@@ -0,0 +1,51 @@
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import base64
+import gdb
+
+from .server import request, capability
+from .startup import send_gdb_with_response, in_gdb_thread
+
+
+@in_gdb_thread
+def _read_memory(addr, count):
+    buf = gdb.selected_inferior().read_memory(addr, count)
+    return base64.b64encode(buf).decode("ASCII")
+
+
+@request("readMemory")
+@capability("supportsReadMemoryRequest")
+def read_memory(*, memoryReference, offset=0, count, **extra):
+    addr = int(memoryReference, 0) + offset
+    buf = send_gdb_with_response(lambda: _read_memory(addr, count))
+    return {
+        "address": hex(addr),
+        "data": buf,
+    }
+
+
+@in_gdb_thread
+def _write_memory(addr, contents):
+    buf = base64.b64decode(contents)
+    gdb.selected_inferior().write_memory(addr, buf)
+
+
+@request("writeMemory")
+@capability("supportsWriteMemoryRequest")
+def write_memory(*, memoryReference, offset=0, data, **extra):
+    addr = int(memoryReference, 0) + offset
+    send_gdb_with_response(lambda: _write_memory(addr, data))
+    return {}

gdb/python/lib/gdb/dap/varref.py

@@ -116,6 +116,7 @@ class VariableReference(BaseReference):
         RESULT_NAME can be used to change how the simple string result
         is emitted in the result dictionary."""
         super().__init__(name)
+        self.value = value
         self.printer = gdb.printing.make_visualizer(value)
         self.result_name = result_name
         # We cache all the children we create.
@@ -160,6 +161,10 @@ class VariableReference(BaseReference):
                 result["indexedVariables"] = num_children
             else:
                 result["namedVariables"] = num_children
+        if self.value.type.code == gdb.TYPE_CODE_PTR:
+            result["memoryReference"] = hex(int(self.value))
+        elif self.value.address is not None:
+            result["memoryReference"] = hex(int(self.value.address))
         return result
 
     @in_gdb_thread

gdb/testsuite/gdb.dap/memory.c

@@ -0,0 +1,25 @@
+/* Copyright 2023 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdint.h>
+
+uint32_t thirty_two = 7;
+
+int main ()
+{
+  return 0;			/* BREAK */
+}

gdb/testsuite/gdb.dap/memory.exp

@@ -0,0 +1,85 @@
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test DAP read/write memory.
+
+load_lib dap-support.exp
+
+standard_testfile
+
+if {[build_executable ${testfile}.exp $testfile] == -1} {
+    return
+}
+
+if {[dap_launch $testfile] == ""} {
+    return
+}
+
+set line [gdb_get_line_number "BREAK"]
+set obj [dap_check_request_and_response "set breakpoint by line number" \
+	     setBreakpoints \
+	     [format {o source [o path [%s]] breakpoints [a [o line [i %d]]]} \
+		  [list s $srcfile] $line]]
+set line_bpno [dap_get_breakpoint_number $obj]
+
+dap_check_request_and_response "start inferior" configurationDone
+dap_wait_for_event_and_check "inferior started" thread "body reason" started
+
+dap_wait_for_event_and_check "stopped at line breakpoint" stopped \
+    "body reason" breakpoint \
+    "body hitBreakpointIds" $line_bpno
+
+set obj [dap_check_request_and_response "evaluate global" \
+	     evaluate {o expression [s thirty_two]}]
+dap_match_values "global value" [lindex $obj 0] "body result" 7
+
+set addr [dict get [lindex $obj 0] body memoryReference]
+
+set obj [dap_check_request_and_response "read memory" \
+	     readMemory [format {o memoryReference [s %s] count [i 4]} $addr]]
+
+set bytes [binary decode base64 [dict get [lindex $obj 0] body data]]
+gdb_assert {[string length $bytes] == 4}
+
+set newbytes ""
+set zeros 0
+set sevens 0
+set others 0
+foreach byte [split $bytes ""] {
+    if {$byte == "\0"} {
+	incr zeros
+	append newbytes $byte
+    } elseif {$byte == "\x7"} {
+	incr sevens
+	append newbytes "\x8"
+    } else {
+	incr others
+    }
+}
+gdb_assert {$zeros == 3}
+gdb_assert {$sevens == 1}
+gdb_assert {$others == 0}
+
+set encoded [binary encode base64 $newbytes]
+
+set obj [dap_check_request_and_response "write memory" \
+	     writeMemory [format {o memoryReference [s %s] count [i 4] data [s %s]} \
+			      $addr $encoded]]
+
+set obj [dap_check_request_and_response "re-evaluate global" \
+	     evaluate {o expression [s thirty_two]}]
+dap_match_values "updated global value" [lindex $obj 0] "body result" 8
+
+dap_shutdown