[PATCH] aarch64-core.xml: 32-bit cpsr -> 64-bit pstate

[Yao Qi <qiyaoltc at gmail dot com>]

This patch is to change 32-bit cpsr to 64-bit pstate in aarch64 target
description.

When aarch64 GDB port was added into GDB, cpsr is 32-bit in
aarch64-core.xml.  Andrew Pinski changed it to 64-bit
https://sourceware.org/ml/gdb-patches/2013-12/msg00720.html but forget
updating GDBserver side.  As a result, GDB thinks cpsr is 64-bit, but
GDBserver still thinks it is 32-bit, so contents of registers after
cpster, such as floating point registers, are wrong.  Catalin Udma
gave a patch https://sourceware.org/ml/gdb-patches/2014-08/msg00193.html
to change cpsr in GDBserver side to 64-bit.  After some discussions,
we decided to revert Andrew's patch, and let cpsr be 32-bit.

A problem "Remote 'g' packet reply is too long:" (when I connect gdb
to kgdb with aarch64 kernel) leads me to the 32-bit vs 64-bit issue
again.

cpsr is 32-bit, but it only exists aarch32 execution state.  As in
ARMv8 reference manual, "A1.3.1 Execution state"

"The A32 and T32
instruction sets include instructions that operate directly on various PSTATE elements, and
instructions that access PSTATE by using the Application Program Status Register (APSR)
or the Current Program Status Register (CPSR)".

In other words, there is no cpsr at all on aarch64 execution state.
On aarch64 execution state, pstate is an abstraction of process state
information, so it has no architecturally defined size or enconding.

However, the architecture does define how the PSTATE is encoded in the
SPSR when taking an exception, and that is the form of PSTATE in
ptrace.  Currently only bits 31:0 of SPSR are defined, but it is only
accessible via MSR/MRS instructions, which always transfer 64-bits,
so on ISA level, it should be regarded as 64-bit.

This change will break the compatibility for <new gdb, old gdbserver>
and <old gdb, new gdbserver>, but current GDB is wrong, we have to fix it.

gdb:

2015-09-03  Yao Qi  <yao.qi@linaro.org>

	* aarch64-tdep.c (aarch64_r_register_names): Rename cpsr to
	pstate.
	* features/aarch64-core.xmli (cpsr): Rename it to pstate, and
	change its size to 64-bit.
	* features/aarch64.c: Regenerate.
	* regformats/aarch64.dat: Likewise.
---
 gdb/aarch64-tdep.c            | 2 +-
 gdb/features/aarch64-core.xml | 2 +-
 gdb/features/aarch64.c        | 2 +-
 gdb/regformats/aarch64.dat    | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 5d8ffd4..04064cb 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -127,7 +127,7 @@ static const char *const aarch64_r_register_names[] =
   "x20", "x21", "x22", "x23",
   "x24", "x25", "x26", "x27",
   "x28", "x29", "x30", "sp",
-  "pc", "cpsr"
+  "pc", "pstate"
 };
 
 /* The FP/SIMD 'V' registers.  */
diff --git a/gdb/features/aarch64-core.xml b/gdb/features/aarch64-core.xml
index c95049c..f0f455f 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="32"/>
+  <reg name="pstate" bitsize="64"/>
 </feature>
diff --git a/gdb/features/aarch64.c b/gdb/features/aarch64.c
index 1e9a99d..643387d 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, 32, "int");
+  tdesc_create_reg (feature, "pstate", 33, 1, NULL, 64, "int");
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.fpu");
   field_type = tdesc_named_type (feature, "ieee_double");
diff --git a/gdb/regformats/aarch64.dat b/gdb/regformats/aarch64.dat
index d4cea04..0db2f3a 100644
--- a/gdb/regformats/aarch64.dat
+++ b/gdb/regformats/aarch64.dat
@@ -36,7 +36,7 @@ expedite:x29,sp,pc
 64:x30
 64:sp
 64:pc
-32:cpsr
+64:pstate
 128:v0
 128:v1
 128:v2
-- 
1.9.1