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From b99b999fc7a0d0888b62e3bdedd0b4855bdf955c Mon Sep 17 00:00:00 2001
From: Shahab Vahedi <shahab@synopsys.com>
Date: Fri, 16 Jul 2021 16:49:15 +0200
Subject: [PATCH 18/20] gdb: Fix numerical field extraction for target
description "flags"
The "val_print_type_code_flags ()" function is responsible for
extraction of fields for "flags" data type. These data types are
used when describing a custom register type in a target description
XML. The logic used for the extraction though is not sound:
unsigned field_len = TYPE_FIELD_BITSIZE (type, field);
ULONGEST field_val
= val >> (TYPE_FIELD_BITPOS (type, field) - field_len + 1);
TYPE_FIELD_BITSIZE: The bit length of the field to be extracted.
TYPE_FIELD_BITPOS: The starting position of the field; 0 is LSB.
val: The register value.
Imagine you have a field that starts at position 1 and its length
is 4 bits. According to the third line of the code snippet the
shifting right would become "val >> -2", or "val >> 0xfff...fe"
to be precise. That will result in a "field_val" of 0.
The correct extraction should be:
ULONGEST field_val = val >> TYPE_FIELD_BITPOS (type, field);
The rest of the algorithm that masks out the higher bits is OK.
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Will be a part of GDB 11:
https://sourceware.org/git?p=binutils-gdb.git;a=commit;h=c9bd98593b785d9bf5f39c7aa74ed0226a23b830
---
gdb/valprint.c | 36 ++++++++++++++++++++++++++++++++++--
1 file changed, 34 insertions(+), 2 deletions(-)
--- a/gdb/valprint.c
+++ b/gdb/valprint.c
@@ -40,6 +40,8 @@
#include "gdbarch.h"
#include "cli/cli-style.h"
#include "count-one-bits.h"
+#include "gdbsupport/selftest.h"
+#include "selftest-arch.h"
/* Maximum number of wchars returned from wchar_iterate. */
#define MAX_WCHARS 4
@@ -1157,8 +1159,7 @@
else
{
unsigned field_len = TYPE_FIELD_BITSIZE (type, field);
- ULONGEST field_val
- = val >> (TYPE_FIELD_BITPOS (type, field) - field_len + 1);
+ ULONGEST field_val = val >> TYPE_FIELD_BITPOS (type, field);
if (field_len < sizeof (ULONGEST) * TARGET_CHAR_BIT)
field_val &= ((ULONGEST) 1 << field_len) - 1;
@@ -3100,10 +3101,41 @@
return {{value_print_option_defs}, opts};
}
+#if GDB_SELF_TEST
+
+/* Test printing of TYPE_CODE_FLAGS values. */
+
+static void
+test_print_flags (gdbarch *arch)
+{
+ type *flags_type = arch_flags_type (arch, "test_type", 32);
+ type *field_type = builtin_type (arch)->builtin_uint32;
+
+ /* Value: 1010 1010
+ Fields: CCCB BAAA */
+ append_flags_type_field (flags_type, 0, 3, field_type, "A");
+ append_flags_type_field (flags_type, 3, 2, field_type, "B");
+ append_flags_type_field (flags_type, 5, 3, field_type, "C");
+
+ value *val = allocate_value (flags_type);
+ gdb_byte *contents = value_contents_writeable (val);
+ store_unsigned_integer (contents, 4, gdbarch_byte_order (arch), 0xaa);
+
+ string_file out;
+ val_print_type_code_flags (flags_type, val, 0, &out);
+ SELF_CHECK (out.string () == "[ A=2 B=1 C=5 ]");
+}
+
+#endif
+
void _initialize_valprint ();
void
_initialize_valprint ()
{
+#if GDB_SELF_TEST
+ selftests::register_test_foreach_arch ("print-flags", test_print_flags);
+#endif
+
cmd_list_element *cmd;
add_basic_prefix_cmd ("print", no_class,
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