diff mbox

aarch64/gdbserver: fix floating point registers display

Message ID 542BCE71.5080308@redhat.com
State New
Headers show

Commit Message

Pedro Alves Oct. 1, 2014, 9:50 a.m. UTC
On 08/21/2014 05:05 PM, Pedro Alves wrote:
> On 08/21/2014 08:26 AM, Yao Qi wrote:
>> On 08/21/2014 02:56 PM, Andrew Pinski wrote:
>>> If we revert the patch is someone going to fix big-endian support then
>>> since that is the original why it was requested.
>>
>> I prefer to revert the patch, because it has problem.  How to fix
>> big-endian support is another issue.
> 
> Agreed.  It just seems to me that gdbserver needs to extract
> the right 32-bits out of the ptrace buffer?

I'm giving the gdb/regformats/ dir some TLC today, and while
regenerating the .dat files stumbled on this.

I've now reverted the patch from mainline and the 7.8 branch, with
the patch below.

Catalin, can I get you to file a PR for the floating point issue,
and add it to:

 https://sourceware.org/gdb/wiki/GDB_7.8_Release

?

(that PR list is what goes into the 7.8.1 release announcement.)

Thanks.

--------
From 63fcc8bcd98a8cd9672dd8672f663662f8caa811 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Wed, 1 Oct 2014 10:44:08 +0100
Subject: [PATCH] Aarch64: Make CPSR a 32-bit register again in the target
 description

This reverts commit a4d9ba85 - 'AARCH64: Change cpsr type to be
64bit.'.

Even though Linux's ptrace exposes CPSR as 64-bit, CPSR is really
32-bit, and basing GDB's fundamentals on a particular OS's ptrace(2)
implementation is a bad idea.

In addition, while that commit intended to fix big endian Aarch64, it
ended up breaking floating point debugging against GDBserver, for both
big and little endian, because it changed the CPSR to be 64-bit in the
features/aarch64-core.xml file, but missed regenerating the
regformats/aarch64.dat file.  If we generate it now, we see this:

  diff --git c/gdb/regformats/aarch64.dat w/gdb/regformats/aarch64.dat
  index afe1028..0d32183 100644
  --- c/gdb/regformats/aarch64.dat
  +++ w/gdb/regformats/aarch64.dat
  @@ -35,7 +35,7 @@ expedite:x29,sp,pc
   64:x30
   64:sp
   64:pc
  -32:cpsr
  +64:cpsr
   128:v0
   128:v1
   128:v2

IOW, that commit left regformats/aarch64.dat still considering CPSR as
32-bits.  regformats/aarch64.dat is used by GDBserver for its internal
regcache layout, and for the g/G packet register block.  See the
generated aarch64.c file in GDBserver's build dir.

So the target description xml file that GDBserver reports to GDB is
now claiming that CPSR is 64-bit, but what GDBserver actually puts in
the g/G register packets is 32-bits.  Because GDB thinks CPSR is
64-bit (because that's what the XML description says), GDB will be
reading the remaining 32-bit bits of CPSR out of v0 (the register
immediately afterwards), and then all the registers that follow CPSR
in the register packet end up wrong in GDB, because they're being read
from the wrong offsets...

gdb/
2014-10-01  Pedro Alves  <palves@redhat.com>

	* features/aarch64-core.xml (cpsr): Change back to 32-bit.
	* features/aarch64.c: Regenerate.
---
 gdb/ChangeLog                 | 5 +++++
 gdb/features/aarch64-core.xml | 2 +-
 gdb/features/aarch64.c        | 2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

Comments

Catalin Udma Oct. 6, 2014, 9:06 a.m. UTC | #1
> I'm giving the gdb/regformats/ dir some TLC today, and while

> regenerating the .dat files stumbled on this.

> 

> I've now reverted the patch from mainline and the 7.8 branch, with

> the patch below.

> 

> Catalin, can I get you to file a PR for the floating point issue,

> and add it to:

> 

>  https://sourceware.org/gdb/wiki/GDB_7.8_Release

> 

> ?

> 

> (that PR list is what goes into the 7.8.1 release announcement.)

> 

> Thanks.

[Catalin Udma] 
Hi,
I filled a PR for this issue:
https://sourceware.org/bugzilla/show_bug.cgi?id=17457

Regards,
Catalin
Pedro Alves Oct. 6, 2014, 12:27 p.m. UTC | #2
On 10/06/2014 10:06 AM, catalin.udma@freescale.com wrote:
>> I've now reverted the patch from mainline and the 7.8 branch, with
>> the patch below.
>>
>> Catalin, can I get you to file a PR for the floating point issue,
>> and add it to:
>>
>>  https://sourceware.org/gdb/wiki/GDB_7.8_Release
>>
>> ?
>>
>> (that PR list is what goes into the 7.8.1 release announcement.)
>>
>> Thanks.
> [Catalin Udma] 
> Hi,
> I filled a PR for this issue:
> https://sourceware.org/bugzilla/show_bug.cgi?id=17457

Thank you.  I've added it to the wiki page.

Thanks,
Pedro Alves
diff mbox

Patch

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 242fe26..f16db06 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@ 
+2014-10-01  Pedro Alves  <palves@redhat.com>
+
+	* features/aarch64-core.xml (cpsr): Change back to 32-bit.
+	* features/aarch64.c: Regenerate.
+
 2014-09-11  Pedro Alves  <palves@redhat.com>
 
 	PR gdb/17347
diff --git a/gdb/features/aarch64-core.xml b/gdb/features/aarch64-core.xml
index dbec6dc..9b45a22 100644
--- a/gdb/features/aarch64-core.xml
+++ b/gdb/features/aarch64-core.xml
@@ -42,5 +42,5 @@ 
   <reg name="sp" bitsize="64" type="data_ptr"/>
 
   <reg name="pc" bitsize="64" type="code_ptr"/>
-  <reg name="cpsr" bitsize="64"/>
+  <reg name="cpsr" bitsize="32"/>
 </feature>
diff --git a/gdb/features/aarch64.c b/gdb/features/aarch64.c
index 31a148e..1e9a99d 100644
--- a/gdb/features/aarch64.c
+++ b/gdb/features/aarch64.c
@@ -50,7 +50,7 @@  initialize_tdesc_aarch64 (void)
   tdesc_create_reg (feature, "x30", 30, 1, NULL, 64, "int");
   tdesc_create_reg (feature, "sp", 31, 1, NULL, 64, "data_ptr");
   tdesc_create_reg (feature, "pc", 32, 1, NULL, 64, "code_ptr");
-  tdesc_create_reg (feature, "cpsr", 33, 1, NULL, 64, "int");
+  tdesc_create_reg (feature, "cpsr", 33, 1, NULL, 32, "int");
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.fpu");
   field_type = tdesc_named_type (feature, "ieee_double");