From: Yao Qi <yao@codesourcery.com>
To: Pedro Alves <palves@redhat.com>
Cc: <gdb-patches@sourceware.org>
Subject: Re: [PATCH] Clear upper bits during sign extension
Date: Thu, 08 Jan 2015 05:40:00 -0000 [thread overview]
Message-ID: <87bnm9u8wx.fsf@codesourcery.com> (raw)
In-Reply-To: <87vbktuu5p.fsf@codesourcery.com> (Yao Qi's message of "Tue, 30 Dec 2014 21:46:58 +0800")
Yao Qi <yao@codesourcery.com> writes:
>> + byte_order = gdbarch_byte_order (get_type_arch (type));
>
> How about getting gdbarch via get_frame_arch (frame)? How about
> removing gdb_sign_extend as it is no longer used?
>
> I'll post a full version on top of yours.
Here is the patch, what do you think?
--
Yao (齐尧)
Subject: [PATCH] always read synthetic pointers as signed integers
I see the error message "access outside bounds of object referenced
via synthetic pointer" in the two fails below of mips gdb testing
print d[-2]^M
access outside bounds of object referenced via synthetic pointer^M
(gdb) FAIL: gdb.dwarf2/implptrconst.exp: print d[-2]
(gdb) print/d p[-1]^M
access outside bounds of object referenced via synthetic pointer^M
(gdb) FAIL: gdb.dwarf2/implptrpiece.exp: print/d p[-1]
in the first test, 'd[-2]' is processed by GDB as '* (&d[-2])'. 'd'
is a synthetic pointer, so its value is zero, the address of 'd[-2]'
is -2. In dwarf2loc.c:indirect_pieced_value,
/* This is an offset requested by GDB, such as value subscripts.
However, due to how synthetic pointers are implemented, this is
always presented to us as a pointer type. This means we have to
sign-extend it manually as appropriate. */
byte_offset = value_as_address (value);
if (TYPE_LENGTH (value_type (value)) < sizeof (LONGEST))
byte_offset = gdb_sign_extend (byte_offset,
8 * TYPE_LENGTH (value_type (value)));
byte_offset += piece->v.ptr.offset;
We know that the value is really an offset instead of address, so the
fix is to extract the value as an (signed) offset.
gdb:
2015-01-08 Pedro Alves <palves@redhat.com>
Yao Qi <yao@codesourcery.com>
* dwarf2loc.c (indirect_pieced_value): Don't call
gdb_sign_extend. Call extract_signed_integer instead.
* utils.c (gdb_sign_extend): Remove.
* utils.h (gdb_sign_extend): Remove declaration.
---
gdb/dwarf2loc.c | 16 +++++++++++-----
gdb/utils.c | 17 -----------------
gdb/utils.h | 5 -----
3 files changed, 11 insertions(+), 27 deletions(-)
diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index 2bd12d6..bdb2160 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -2012,6 +2012,7 @@ indirect_pieced_value (struct value *value)
int i, bit_offset, bit_length;
struct dwarf_expr_piece *piece = NULL;
LONGEST byte_offset;
+ enum bfd_endian byte_order;
type = check_typedef (value_type (value));
if (TYPE_CODE (type) != TYPE_CODE_PTR)
@@ -2056,11 +2057,16 @@ indirect_pieced_value (struct value *value)
/* This is an offset requested by GDB, such as value subscripts.
However, due to how synthetic pointers are implemented, this is
always presented to us as a pointer type. This means we have to
- sign-extend it manually as appropriate. */
- byte_offset = value_as_address (value);
- if (TYPE_LENGTH (value_type (value)) < sizeof (LONGEST))
- byte_offset = gdb_sign_extend (byte_offset,
- 8 * TYPE_LENGTH (value_type (value)));
+ sign-extend it manually as appropriate. Use raw
+ extract_signed_integer directly rather than value_as_address and
+ sign extend afterwards on architectures that would need it
+ (mostly everywhere except MIPS, which has signed addresses) as
+ the later would go through gdbarch_pointer_to_address and thus
+ return a CORE_ADDR with high bits set on architectures that
+ encode address spaces and other things in CORE_ADDR. */
+ byte_order = gdbarch_byte_order (get_frame_arch (frame));
+ byte_offset = extract_signed_integer (value_contents (value),
+ TYPE_LENGTH (type), byte_order);
byte_offset += piece->v.ptr.offset;
gdb_assert (piece);
diff --git a/gdb/utils.c b/gdb/utils.c
index 084db87..72b1e2a 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -3021,23 +3021,6 @@ align_down (ULONGEST v, int n)
return (v & -n);
}
-/* See utils.h. */
-
-LONGEST
-gdb_sign_extend (LONGEST value, int bit)
-{
- gdb_assert (bit >= 1 && bit <= 8 * sizeof (LONGEST));
-
- if (((value >> (bit - 1)) & 1) != 0)
- {
- LONGEST signbit = ((LONGEST) 1) << (bit - 1);
-
- value = (value ^ signbit) - signbit;
- }
-
- return value;
-}
-
/* Allocation function for the libiberty hash table which uses an
obstack. The obstack is passed as DATA. */
diff --git a/gdb/utils.h b/gdb/utils.h
index 0a73864..3debde7 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -340,11 +340,6 @@ extern int myread (int, char *, int);
extern ULONGEST align_up (ULONGEST v, int n);
extern ULONGEST align_down (ULONGEST v, int n);
-/* Sign extend VALUE. BIT is the (1-based) index of the bit in VALUE
- to sign-extend. */
-
-extern LONGEST gdb_sign_extend (LONGEST value, int bit);
-
/* Resource limits used by getrlimit and setrlimit. */
enum resource_limit_kind
--
1.9.3
next prev parent reply other threads:[~2015-01-08 5:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-29 1:13 Yao Qi
2014-12-29 3:07 ` Joel Brobecker
2014-12-29 3:38 ` Yao Qi
2014-12-29 3:53 ` Joel Brobecker
2014-12-29 5:29 ` Doug Evans
2014-12-29 6:27 ` Yao Qi
2014-12-29 10:48 ` Pedro Alves
2014-12-30 9:20 ` Yao Qi
2014-12-30 12:20 ` Pedro Alves
2014-12-30 13:47 ` Yao Qi
2015-01-08 5:40 ` Yao Qi [this message]
2015-01-08 10:42 ` Pedro Alves
2015-01-08 13:06 ` Yao Qi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87bnm9u8wx.fsf@codesourcery.com \
--to=yao@codesourcery.com \
--cc=gdb-patches@sourceware.org \
--cc=palves@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).