[PATCH v3 6/6] Use correct inferior in Inferior.read_memory et al

Tom Tromey via Gdb-patches
2023-07-13T14:06:57Z

A user noticed that Inferior.read_memory and a few other Python APIs
will always use the currently selected inferior, not the one passed to
the call.

This patch fixes the bug by arranging to switch to the inferior. I
found this same issue in several APIs, so this fixes them all.

I also added a few missing calls to INFPY_REQUIRE_VALID to these
methods.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30615
---
gdb/python/py-inferior.c | 43 ++++++++++++++++++++++++++------
gdb/testsuite/gdb.python/py-inferior.exp | 26 +++++++++++++++++++
2 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index af8bd8855a3..f6000b944da 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -30,6 +30,7 @@
#include "gdbsupport/gdb_signals.h"
#include "py-event.h"
#include "py-stopevent.h"
+#include "progspace-and-thread.h"
#include <unordered_map>

using thread_map_t
@@ -528,11 +529,14 @@ gdbpy_inferiors (PyObject *unused, PyObject *unused2)
static PyObject *
infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
{
+ inferior_object *inf = (inferior_object *) self;
CORE_ADDR addr, length;
gdb::unique_xmalloc_ptr<gdb_byte> buffer;
PyObject *addr_obj, *length_obj;
static const char *keywords[] = { "address", "length", NULL };

+ INFPY_REQUIRE_VALID (inf);
+
if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "OO", keywords,
&addr_obj, &length_obj))
return NULL;
@@ -543,6 +547,11 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)

try
{
+ /* Use this scoped-restore because we want to be able to read
+ memory from an unwinder. */
+ scoped_restore_current_inferior_for_memory restore_inferior
+ (inf->inferior, any_thread_of_inferior (inf->inferior)->ptid);
+
buffer.reset ((gdb_byte *) xmalloc (length));

read_memory (addr, buffer.get (), length);
@@ -565,6 +574,7 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
static PyObject *
infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)
{
+ inferior_object *inf = (inferior_object *) self;
struct gdb_exception except;
Py_ssize_t buf_len;
const gdb_byte *buffer;
@@ -573,6 +583,8 @@ infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)
static const char *keywords[] = { "address", "buffer", "length", NULL };
Py_buffer pybuf;

+ INFPY_REQUIRE_VALID (inf);
+
if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "Os*|O", keywords,
&addr_obj, &pybuf, &length_obj))
return NULL;
@@ -591,6 +603,13 @@ infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)

try
{
+ /* It's probably not too important to avoid invalidating the
+ frame cache when writing memory, but this scoped-restore is
+ still used here, just to keep the code similar to other code
+ in this file. */
+ scoped_restore_current_inferior_for_memory restore_inferior
+ (inf->inferior, any_thread_of_inferior (inf->inferior)->ptid);
+
write_memory_with_notification (addr, buffer, length);
}
catch (gdb_exception &ex)
@@ -604,7 +623,7 @@ infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)
}

/* Implementation of
- gdb.search_memory (address, length, pattern). ADDRESS is the
+ Inferior.search_memory (address, length, pattern). ADDRESS is the
address to start the search. LENGTH specifies the scope of the
search from ADDRESS. PATTERN is the pattern to search for (and
must be a Python object supporting the buffer protocol).
@@ -614,6 +633,7 @@ infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)
static PyObject *
infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
{
+ inferior_object *inf = (inferior_object *) self;
struct gdb_exception except;
CORE_ADDR start_addr, length;
static const char *keywords[] = { "address", "length", "pattern", NULL };
@@ -624,6 +644,8 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
int found = 0;
Py_buffer pybuf;

+ INFPY_REQUIRE_VALID (inf);
+
if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "OOs*", keywords,
&start_addr_obj, &length_obj,
&pybuf))
@@ -656,6 +678,13 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)

try
{
+ /* It's probably not too important to avoid invalidating the
+ frame cache when searching memory, but this scoped-restore is
+ still used here, just to keep the code similar to other code
+ in this file. */
+ scoped_restore_current_inferior_for_memory restore_inferior
+ (inf->inferior, any_thread_of_inferior (inf->inferior)->ptid);
+
found = target_search_memory (start_addr, length,
buffer, pattern_size,
&found_addr);
@@ -910,12 +939,12 @@ infpy_get_main_name (PyObject *self, void *closure)
try
{
/* This is unfortunate but the implementation of main_name can
- reach into memory. */
- scoped_restore_current_inferior restore_inferior;
- set_current_inferior (inf->inferior);
-
- scoped_restore_current_program_space restore_current_progspace;
- set_current_program_space (inf->inferior->pspace);
+ reach into memory. It's probably not too important to avoid
+ invalidating the frame cache here, but this scoped-restore is
+ still used, just to keep the code similar to other code in
+ this file. */
+ scoped_restore_current_inferior_for_memory restore_inferior
+ (inf->inferior, any_thread_of_inferior (inf->inferior)->ptid);

name = main_name ();
}
diff --git a/gdb/testsuite/gdb.python/py-inferior.exp b/gdb/testsuite/gdb.python/py-inferior.exp
index 8762b6992ca..eb501838117 100644
--- a/gdb/testsuite/gdb.python/py-inferior.exp
+++ b/gdb/testsuite/gdb.python/py-inferior.exp
@@ -91,6 +91,7 @@ gdb_py_test_silent_cmd "python addr = gdb.selected_frame ().read_var ('str')" \
gdb_test "python astr = gdb.inferiors()\[0\].read_memory (addr, 5); print(astr)" \
"<memory at $hex>" \
"read str contents"
+gdb_test "python print(astr\[0\])" .*
gdb_py_test_silent_cmd "python a = bytes('a', 'ascii')" "" 0
gdb_py_test_silent_cmd "python astr\[1\] = a" "change str" 0
gdb_py_test_silent_cmd "python gdb.inferiors()\[0\].write_memory (addr, astr)" \
@@ -98,6 +99,10 @@ gdb_py_test_silent_cmd "python gdb.inferiors()\[0\].write_memory (addr, astr)" \
gdb_test "print str" " = \"hallo, testsuite\"" \
"ensure str was changed in the inferior"

+# Add a new inferior here, so we can test that operations work on the
+# correct inferior.
+set num [add_inferior]
+
# Test memory search.

set hex_number {0x[0-9a-fA-F][0-9a-fA-F]*}
@@ -115,6 +120,9 @@ with_test_prefix "string" {
gdb_test_no_output "py start_addr = search_buf.address"
gdb_test_no_output "py length = search_buf.type.sizeof"

+ # Switch to the new inferior before testing.
+ gdb_test "inferior $num" ".*" "switch to inferior $num"
+
gdb_test "py print (gdb.inferiors()\[0\].search_memory (start_addr, length, 'aaa'))" \
"${one_pattern_found}" "find string pattern"

@@ -128,6 +136,24 @@ with_test_prefix "string" {
"${one_pattern_found}" "pattern found at end of range"
}

+# While still in the new inferior, test reading and writing memory
+# again.
+gdb_test "python astr = gdb.inferiors()\[0\].read_memory (addr, 5); print(astr)" \
+ "<memory at $hex>" \
+ "read str while other inferior selected"
+gdb_test "python print(astr\[1\])" "b'a'" \
+ "print a character from the string"
+gdb_py_test_silent_cmd "python astr\[1\] = b'X'" "change str again" 0
+gdb_py_test_silent_cmd "python gdb.inferiors()\[0\].write_memory (addr, astr)" \
+ "write str while other inferior selected" 1
+
+gdb_test "inferior 1" ".*" "switch back to inferior 1"
+
+gdb_test "print str" " = \"hXllo, testsuite\"" \
+ "ensure str was changed while other inferior selected"
+
+gdb_test_no_output "remove-inferiors $num" "remove-inferiors $num"
+
# Import struct to pack the following patterns.
gdb_test_no_output "py from struct import *"

--
2.40.1