diff mbox

[review,ARM,Thumb] Fix disassembling bug after reloading a symbol file

Message ID gerrit.1572442722000.I22c3e6ebe9bfedad66d56fe9656994fa1761c485@gnutoolchain-gerrit.osci.io
State New, archived
Headers

Commit Message

Simon Marchi (Code Review) Oct. 30, 2019, 1:38 p.m. UTC 
  Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................

[ARM, Thumb] Fix disassembling bug after reloading a symbol file

The speed optimization from commit 5f6cac4085c95c5339b9549dc06d4f9184184fa6
made GDB skip reloading all symbols when the same symbol file is reloaded.

As a result, ARM targets only read the mapping symbols the first time we
load a symbol file. When reloaded, the speed optimization above will
cause an early return and gdbarch_record_special_symbol won't be called to
save mapping symbol data, which in turn affects disassembling of thumb
instructions.

First load and correct disassemble output:

Dump of assembler code for function main:
    0x0000821c <+0>:     bx      pc
    0x0000821e <+2>:     nop
    0x00008220 <+4>:     mov     r0, #0
    0x00008224 <+8>:     bx      lr

Second load and incorrect disassemble output:

Dump of assembler code for function main:
    0x0000821c <+0>:     bx      pc
    0x0000821e <+2>:     nop
    0x00008220 <+4>:     movs    r0, r0
    0x00008222 <+6>:     b.n     0x8966
    0x00008224 <+8>:     vrhadd.u16      d14, d14, d31

This happens because the mapping symbol data is stored in an objfile_key-based
container, and that data isn't preserved across the two symbol loading
operations.

The following patch fixes this by storing the mapping symbol data in a
bfd_key-based container, which doesn't change as long as the bfd is the same.

I've also added a new test to verify the correct disassemble output.

OK?

gdb/ChangeLog:

2019-01-29  Luis Machado  <luis.machado@linaro.org>

	* arm-tdep.c (arm_per_objfile): Rename to ...
	(arm_per_bfd): ... this.
	(arm_objfile_data_key): Rename to ...
	(arm_bfd_data_key): ... this.
	(arm_find_mapping_symbol): Adjust access to new bfd_key-based
	data.
	(arm_record_special_symbol): Likewise.

gdb/testsuite/ChangeLog:

2019-01-29  Luis Machado  <luis.machado@linaro.org>

	* gdb.arch/pr25124.S: New file.
	* gdb.arch/pr25124.exp: New file.

Signed-off-by: Luis Machado <luis.machado@linaro.org>
Change-Id: I22c3e6ebe9bfedad66d56fe9656994fa1761c485
---
M gdb/arm-tdep.c
A gdb/testsuite/gdb.arch/pr25124.S
A gdb/testsuite/gdb.arch/pr25124.exp
3 files changed, 86 insertions(+), 10 deletions(-)

Comments

Simon Marchi (Code Review) Oct. 30, 2019, 2 p.m. UTC | #1 
Andrew Burgess has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................


Patch Set 1:

(3 comments)

Basically fine, few minor issues I think need addressing before it can be merged.

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/arm-tdep.c 
File gdb/arm-tdep.c:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/arm-tdep.c@101 
PS1, Line 101: 
 92 | struct arm_per_bfd
 93 | {
 94 |   explicit arm_per_bfd (size_t num_sections)
 95 |   : section_maps (new arm_mapping_symbol_vec[num_sections]),
 96 |     section_maps_sorted (new bool[num_sections] ())
 97 |   {}
 98 | 
 99 |   DISABLE_COPY_AND_ASSIGN (arm_per_bfd);
100 | 
101 |   /* Information about mapping symbols ($a, $d, $t) in the objfile.

Should this mention of objfile be changed to "bfd" or "bfd object"?


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.S 
File gdb/testsuite/gdb.arch/pr25124.S:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.S@4 
PS1, Line 4: 
1 | /* Test proper disassembling of ARM thumb instructions when reloading a symbol
2 |    file.
3 | 
4 |    Copyright 2012-2019 Free Software Foundation, Inc.

This year should be 2019 only unless (1) it's a copy of another file that was added in 2012, or (2) this patch was originally submitted in 2012.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.exp 
File gdb/testsuite/gdb.arch/pr25124.exp:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.exp@33 
PS1, Line 33: 
24 | standard_testfile .S
25 | 
26 | if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable debug] != "" } {
27 |     untested "failed to compile"
28 |     return -1
29 | }
30 | 
31 | gdb_test "x /i main+8"
32 | 	"$hex <main\\+8>:\[ \t\]+bx\[ \t\]+lr"
33 | 	"disassemble thumb instruction (1st try)"

Maybe I'm going crazy, but doesn't like 31 and 32 need to end in a trailing backslash?  The next call to gdb_test does, and then the third below again, no backslash.  I don't have an ARM target to hand, but does this test run correctly like this?
Simon Marchi (Code Review) Oct. 30, 2019, 2:11 p.m. UTC | #2 
Luis Machado has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................


Patch Set 1:

(3 comments)

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/arm-tdep.c 
File gdb/arm-tdep.c:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/arm-tdep.c@101 
PS1, Line 101: 
 92 | struct arm_per_bfd
 93 | {
 94 |   explicit arm_per_bfd (size_t num_sections)
 95 |   : section_maps (new arm_mapping_symbol_vec[num_sections]),
 96 |     section_maps_sorted (new bool[num_sections] ())
 97 |   {}
 98 | 
 99 |   DISABLE_COPY_AND_ASSIGN (arm_per_bfd);
100 | 
101 |   /* Information about mapping symbols ($a, $d, $t) in the objfile.

> Should this mention of objfile be changed to "bfd" or "bfd object"?

I thought about it, but the symbols themselves are contained in the objfile itself, though we're storing additional information inferred from said symbols in the bfd container.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.S 
File gdb/testsuite/gdb.arch/pr25124.S:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.S@4 
PS1, Line 4: 
1 | /* Test proper disassembling of ARM thumb instructions when reloading a symbol
2 |    file.
3 | 
4 |    Copyright 2012-2019 Free Software Foundation, Inc.

> This year should be 2019 only unless (1) it's a copy of another file that was added in 2012, or (2)  […]

This is in fact a copy of gdb.arch/thumb-bx-pc.S, hence why i left it that way.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.exp 
File gdb/testsuite/gdb.arch/pr25124.exp:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/1/gdb/testsuite/gdb.arch/pr25124.exp@33 
PS1, Line 33: 
24 | standard_testfile .S
25 | 
26 | if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable debug] != "" } {
27 |     untested "failed to compile"
28 |     return -1
29 | }
30 | 
31 | gdb_test "x /i main+8"
32 | 	"$hex <main\\+8>:\[ \t\]+bx\[ \t\]+lr"
33 | 	"disassemble thumb instruction (1st try)"

> Maybe I'm going crazy, but doesn't like 31 and 32 need to end in a trailing backslash?  The next cal […]

They do. I borked it just before submission, having noticed the overly long line and breaking it into multiple lines. I'll fix it.

As for running it effectively, i haven't due to the lack of access to a box running arm 32-bit. It doesn't seem we have buildbots running those either.
Simon Marchi (Code Review) Oct. 30, 2019, 3:15 p.m. UTC | #3 
Tom Tromey has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................


Patch Set 2:

(2 comments)

Thank you for the patch.  I had one question that I think should
be answered before landing; plus one nit.

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2//COMMIT_MSG 
Commit Message:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2//COMMIT_MSG@62 
PS2, Line 62: 
53 | 	(arm_bfd_data_key): ... this.
54 | 	(arm_find_mapping_symbol): Adjust access to new bfd_key-based
55 | 	data.
56 | 	(arm_record_special_symbol): Likewise.
57 | 
58 | gdb/testsuite/ChangeLog:
59 | 
60 | 2019-01-29  Luis Machado  <luis.machado@linaro.org>
61 | 
62 | 	* gdb.arch/pr25124.S: New file.

If there's a PR open for this, then each ChangeLog should
mention it, like "PR arch/25124".  This syntax lets the
commit script log the commit in bugzilla.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2/gdb/arm-tdep.c 
File gdb/arm-tdep.c:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2/gdb/arm-tdep.c@117 
PS2, Line 117: 
108 |      symbol value (address).  */
109 |   std::unique_ptr<arm_mapping_symbol_vec[]> section_maps;
110 | 
111 |   /* For each corresponding element of section_maps above, is this vector
112 |      sorted.  */
113 |   std::unique_ptr<bool[]> section_maps_sorted;
114 | };
115 | 
116 | /* Per-bfd data used for mapping symbols.  */
117 | static bfd_key<arm_per_bfd> arm_bfd_data_key;

I wonder if `arm_exidx_data_key` needs this treatment as well?
Simon Marchi (Code Review) Oct. 30, 2019, 3:22 p.m. UTC | #4 
Luis Machado has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................


Patch Set 2:

(2 comments)

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2//COMMIT_MSG 
Commit Message:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2//COMMIT_MSG@62 
PS2, Line 62: 
53 | 	(arm_bfd_data_key): ... this.
54 | 	(arm_find_mapping_symbol): Adjust access to new bfd_key-based
55 | 	data.
56 | 	(arm_record_special_symbol): Likewise.
57 | 
58 | gdb/testsuite/ChangeLog:
59 | 
60 | 2019-01-29  Luis Machado  <luis.machado@linaro.org>
61 | 
62 | 	* gdb.arch/pr25124.S: New file.

> If there's a PR open for this, then each ChangeLog should […]

Great. I'll add it. Thanks for the catching that.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2/gdb/arm-tdep.c 
File gdb/arm-tdep.c:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447/2/gdb/arm-tdep.c@117 
PS2, Line 117: 
108 |      symbol value (address).  */
109 |   std::unique_ptr<arm_mapping_symbol_vec[]> section_maps;
110 | 
111 |   /* For each corresponding element of section_maps above, is this vector
112 |      sorted.  */
113 |   std::unique_ptr<bool[]> section_maps_sorted;
114 | };
115 | 
116 | /* Per-bfd data used for mapping symbols.  */
117 | static bfd_key<arm_per_bfd> arm_bfd_data_key;

> I wonder if `arm_exidx_data_key` needs this treatment as well?

I did go through it when doing the change. It seems a bit more complicated, and it is attached to an observer, but i think it makes sense to convert it too.

I'll make a separate patch for it, since, unlike this particular case, the exidx processing doesn't suffer from not getting updated when we reload the objfile.
Simon Marchi (Code Review) Oct. 31, 2019, 4:45 p.m. UTC | #5 
Luis Machado has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................


Patch Set 5:

I've now updated the testcase, with the help of the tryserver, and made sure it is passing accordingly. It was erroring out before.
Simon Marchi (Code Review) Nov. 1, 2019, 1:09 a.m. UTC | #6 
Andrew Burgess has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/447
......................................................................


Patch Set 5: Code-Review+2

LGTM.

Tom's question about arm_exidx_data_key is address by you other patch https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/448.
diff mbox

Patch

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 8694618..ac7f951 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -89,14 +89,14 @@ 
 
 typedef std::vector<arm_mapping_symbol> arm_mapping_symbol_vec;
 
-struct arm_per_objfile
+struct arm_per_bfd
 {
-  explicit arm_per_objfile (size_t num_sections)
+  explicit arm_per_bfd (size_t num_sections)
   : section_maps (new arm_mapping_symbol_vec[num_sections]),
     section_maps_sorted (new bool[num_sections] ())
   {}
 
-  DISABLE_COPY_AND_ASSIGN (arm_per_objfile);
+  DISABLE_COPY_AND_ASSIGN (arm_per_bfd);
 
   /* Information about mapping symbols ($a, $d, $t) in the objfile.
 
@@ -113,8 +113,8 @@ 
   std::unique_ptr<bool[]> section_maps_sorted;
 };
 
-/* Per-objfile data used for mapping symbols.  */
-static objfile_key<arm_per_objfile> arm_objfile_data_key;
+/* Per-bfd data used for mapping symbols.  */
+static bfd_key<arm_per_bfd> arm_bfd_data_key;
 
 /* The list of available "set arm ..." and "show arm ..." commands.  */
 static struct cmd_list_element *setarmcmdlist = NULL;
@@ -350,7 +350,7 @@ 
   sec = find_pc_section (memaddr);
   if (sec != NULL)
     {
-      arm_per_objfile *data = arm_objfile_data_key.get (sec->objfile);
+      arm_per_bfd *data = arm_bfd_data_key.get (sec->objfile->obfd);
       if (data != NULL)
 	{
 	  unsigned int section_idx = sec->the_bfd_section->index;
@@ -8560,17 +8560,17 @@ 
 			   asymbol *sym)
 {
   const char *name = bfd_asymbol_name (sym);
-  struct arm_per_objfile *data;
+  struct arm_per_bfd *data;
   struct arm_mapping_symbol new_map_sym;
 
   gdb_assert (name[0] == '$');
   if (name[1] != 'a' && name[1] != 't' && name[1] != 'd')
     return;
 
-  data = arm_objfile_data_key.get (objfile);
+  data = arm_bfd_data_key.get (objfile->obfd);
   if (data == NULL)
-    data = arm_objfile_data_key.emplace (objfile,
-					 objfile->obfd->section_count);
+    data = arm_bfd_data_key.emplace (objfile->obfd,
+				     objfile->obfd->section_count);
   arm_mapping_symbol_vec &map
     = data->section_maps[bfd_asymbol_section (sym)->index];
 
diff --git a/gdb/testsuite/gdb.arch/pr25124.S b/gdb/testsuite/gdb.arch/pr25124.S
new file mode 100644
index 0000000..79f82c7
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/pr25124.S
@@ -0,0 +1,35 @@ 
+/* Test proper disassembling of ARM thumb instructions when reloading a symbol
+   file.
+
+   Copyright 2012-2019 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/>.  */
+
+	.syntax unified
+	.thumb
+	.text
+	.p2align 2
+	.global	main
+	.thumb
+	.thumb_func
+	.type main, %function
+main:
+	bx	pc
+	nop
+.code 32
+	mov	r0, #0
+	bx	lr
+	.size	main, .-main
diff --git a/gdb/testsuite/gdb.arch/pr25124.exp b/gdb/testsuite/gdb.arch/pr25124.exp
new file mode 100644
index 0000000..a5b7bf6
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/pr25124.exp
@@ -0,0 +1,41 @@ 
+# Copyright 2019 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 proper disassembling of ARM thumb instructions when reloading a symbol
+# file.
+
+if {![is_aarch32_target]} then {
+    verbose "Skipping ARM tests."
+    return
+}
+
+standard_testfile .S
+
+if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable debug] != "" } {
+    untested "failed to compile"
+    return -1
+}
+
+gdb_test "x /i main+8"
+	"$hex <main\\+8>:\[ \t\]+bx\[ \t\]+lr"
+	"disassemble thumb instruction (1st try)"
+
+gdb_test "file $binfile" \
+	"Reading symbols from.*" \
+	"reload symbol file"
+
+gdb_test "x /i main+8"
+	"$hex <main\\+8>:\[ \t\]+bx\[ \t\]+lr"
+	"disassemble thumb instruction (2nd try)"