[binutils-gdb] gdb/x86: Fix write out of mxcsr register for xsave targets

[Andrew Burgess <aburgess at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=cf4912ae570ceae019b344785e4eeaf8cf273df3

commit cf4912ae570ceae019b344785e4eeaf8cf273df3
Author: Andrew Burgess <andrew.burgess@embecosm.com>
Date:   Fri May 11 00:45:55 2018 +0100

    gdb/x86: Fix write out of mxcsr register for xsave targets
    
    In commit:
    
      commit 8ee22052f690c007556b97eed59f49350ece5ca9
      Author: Andrew Burgess <andrew.burgess@embecosm.com>
      Date:   Thu May 3 17:46:14 2018 +0100
    
          gdb/x86: Handle kernels using compact xsave format
    
    in two places FXSAVE_ADDR was used instead of FXSAVE_MXCSR_ADDR to get
    the address of the mxcsr register within the xsave buffer.  This will
    mean we are potentially accessing the wrong location within the xsave
    buffer.
    
    There are no tests included with this patch.  The first mistake would
    only trigger an issue if/when the user tries to manually set the mxcsr
    register to a value that matches the random (value off stack) value
    that is in the xsave buffer, in this case the change by the user will
    go unnoticed by GDB, and the default value of mxcsr will be preserved.
    
    The second mistake only happens on the code path where all x87
    registers are being written out of the register cache.  I'm not sure
    how to trigger that code path.
    
    gdb/ChangeLog:
    
    	* i387-tdep.c (i387_collect_xsave): Use FXSAVE_MXCSR_ADDR not
    	FXSAVE_ADDR for the mxcsr register.

Diff:
---
 gdb/ChangeLog   | 5 +++++
 gdb/i387-tdep.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a3a133c..67610d7 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-11  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* i387-tdep.c (i387_collect_xsave): Use FXSAVE_MXCSR_ADDR not
+	FXSAVE_ADDR for the mxcsr register.
+
 2018-05-11  Max Filippov  <jcmvbkbc@gmail.com>
 
 	* configure.tgt (xtensa*-*-linux*): Drop gdb_target definition.
diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c
index aca70c1..3effc35 100644
--- a/gdb/i387-tdep.c
+++ b/gdb/i387-tdep.c
@@ -1490,7 +1490,7 @@ i387_collect_xsave (const struct regcache *regcache, int regnum,
 	 require clearing.  */
       if ((clear_bv & (X86_XSTATE_AVX | X86_XSTATE_SSE))
 	  == (X86_XSTATE_AVX | X86_XSTATE_SSE))
-	store_unsigned_integer (FXSAVE_ADDR (tdep, regs, i), 2, byte_order,
+	store_unsigned_integer (FXSAVE_MXCSR_ADDR (regs), 2, byte_order,
 				I387_MXCSR_INIT_VAL);
 
       if ((clear_bv & X86_XSTATE_X87))
@@ -1643,7 +1643,7 @@ i387_collect_xsave (const struct regcache *regcache, int regnum,
 	{
 	  i = I387_MXCSR_REGNUM (tdep);
 	  regcache_raw_collect (regcache, i, raw);
-	  p = FXSAVE_ADDR (tdep, regs, i);
+	  p = FXSAVE_MXCSR_ADDR (regs);
 	  if (memcmp (raw, p, 4))
 	    {
 	      /* Now, we need to mark one of either SSE of AVX as enabled.