[PATCH] [ARM] Clear reserved bits in CPSR

[Yao Qi <qiyaoltc@gmail.com>]

Bits 20 ~ 23 of CPSR are reserved (RAZ, read as zero), but they are not
zero if the arm program runs on aarch64-linux.  AArch64 tracer gets PSTATE
from arm 32-bit tracee as CPSR, but bits 20 ~ 23 are used in PSTATE.  I
think kernel should clear these bits when it is read through ptrace, but
the fix in user space is still needed.

This patch fixes these two fails,

-FAIL: gdb.reverse/insn-reverse.exp: ext_reg_push_pop: compare registers on insn 0:vldr	d7, [r11, #-12]
-FAIL: gdb.reverse/insn-reverse.exp: ext_reg_push_pop: compare registers on insn 0:vldr	d7, [r7]

Regression tested on both native and remote on aarch64-linux.

gdb:

2016-04-22  Yao Qi  <yao.qi@linaro.org>

	* aarch32-linux-nat.c (aarch32_gp_regcache_supply): Clear CPSR
	bits 20 to 23.

gdb/gdbserver:

2016-04-22  Yao Qi  <yao.qi@linaro.org>

	* linux-aarch32-low.c (arm_store_gregset): Clear CPSR bits 20
	to 23.
---
 gdb/aarch32-linux-nat.c           | 6 +++++-
 gdb/gdbserver/linux-aarch32-low.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/gdb/aarch32-linux-nat.c b/gdb/aarch32-linux-nat.c
index 568dfa6..97b319b 100644
--- a/gdb/aarch32-linux-nat.c
+++ b/gdb/aarch32-linux-nat.c
@@ -37,7 +37,11 @@ aarch32_gp_regcache_supply (struct regcache *regcache, uint32_t *regs,
     regcache_raw_supply (regcache, regno, &regs[regno]);
 
   if (arm_apcs_32)
-    regcache_raw_supply (regcache, ARM_PS_REGNUM, &regs[ARM_CPSR_GREGNUM]);
+    {
+      /* Clear reserved bits bit 20 to bit 23.  */
+      regs[ARM_CPSR_GREGNUM] = 0xff0fffff & regs[ARM_CPSR_GREGNUM];
+      regcache_raw_supply (regcache, ARM_PS_REGNUM, &regs[ARM_CPSR_GREGNUM]);
+    }
   else
     regcache_raw_supply (regcache, ARM_PS_REGNUM, &regs[ARM_PC_REGNUM]);
 
diff --git a/gdb/gdbserver/linux-aarch32-low.c b/gdb/gdbserver/linux-aarch32-low.c
index 0c4b140..5087550 100644
--- a/gdb/gdbserver/linux-aarch32-low.c
+++ b/gdb/gdbserver/linux-aarch32-low.c
@@ -77,6 +77,7 @@ arm_store_gregset (struct regcache *regcache, const void *buf)
   int i;
   char zerobuf[8];
   const uint32_t *regs = (const uint32_t *) buf;
+  uint32_t cpsr = regs[ARM_CPSR_GREGNUM];
 
   memset (zerobuf, 0, 8);
   for (i = ARM_A1_REGNUM; i <= ARM_PC_REGNUM; i++)
@@ -85,7 +86,9 @@ arm_store_gregset (struct regcache *regcache, const void *buf)
   for (; i < ARM_PS_REGNUM; i++)
     supply_register (regcache, i, zerobuf);
 
-  supply_register (regcache, ARM_PS_REGNUM, &regs[ARM_CPSR_GREGNUM]);
+  /* Clear reserved bits bit 20 to bit 23.  */
+  cpsr = 0xff0fffff & cpsr;
+  supply_register (regcache, ARM_PS_REGNUM, &cpsr);
 }
 
 /* Collect NUM number of VFP registers from REGCACHE to buffer BUF.  */
-- 
1.9.1