From 098dbe61246fd65ea5e3825d77afb31d52c43153 Mon Sep 17 00:00:00 2001
From: Andreas Arnez <arnez@linux.vnet.ibm.com>
Date: Fri, 12 Dec 2014 14:14:20 +0100
Subject: [PATCH 7/9] gdbserver: Prevent stale/random values in register cache

When fetch_inferior_registers does not update all registers, this
patch assures that no stale register values remain in the register
cache.  On Linux platforms using the regsets interface, when one of
the ptrace calls used for fetching the register values returns an
error, this patch also avoids copying the random data returned from
ptrace into the register cache.  All unfetched registers are marked
"unavailable" instead.

gdb/gdbserver/ChangeLog:

	* linux-low.c (regsets_fetch_inferior_registers): Do not invoke
	the regset's store function when ptrace returned an error.
	* regcache.c (get_thread_regcache): Invalidate register cache
	before fetching inferior's registers.
---
 gdb/gdbserver/ChangeLog   |  7 +++++++
 gdb/gdbserver/linux-low.c | 11 ++++++-----
 gdb/gdbserver/regcache.c  |  3 +++
 3 files changed, 16 insertions(+), 5 deletions(-)

Index: gdb-7.6.1/gdb/gdbserver/linux-low.c
===================================================================
--- gdb-7.6.1.orig/gdb/gdbserver/linux-low.c
+++ gdb-7.6.1/gdb/gdbserver/linux-low.c
@@ -4080,8 +4080,6 @@ regsets_fetch_inferior_registers (struct
 	      /* If we get EIO on a regset, do not try it again for
 		 this process.  */
 	      disabled_regsets[regset - target_regsets] = 1;
-	      free (buf);
-	      continue;
 	    }
 	  else
 	    {
@@ -4091,9 +4089,12 @@ regsets_fetch_inferior_registers (struct
 	      perror (s);
 	    }
 	}
-      else if (regset->type == GENERAL_REGS)
-	saw_general_regs = 1;
-      regset->store_function (regcache, buf);
+      else
+	{
+	  if (regset->type == GENERAL_REGS)
+	    saw_general_regs = 1;
+	  regset->store_function (regcache, buf);
+	}
       regset ++;
       free (buf);
     }
Index: gdb-7.6.1/gdb/gdbserver/regcache.c
===================================================================
--- gdb-7.6.1.orig/gdb/gdbserver/regcache.c
+++ gdb-7.6.1/gdb/gdbserver/regcache.c
@@ -47,6 +47,9 @@ get_thread_regcache (struct thread_info
       struct thread_info *saved_inferior = current_inferior;
 
       current_inferior = thread;
+      /* Invalidate all registers, to prevent stale left-overs.  */
+      memset (regcache->register_status, REG_UNAVAILABLE,
+	      num_registers);
       fetch_inferior_registers (regcache, -1);
       current_inferior = saved_inferior;
       regcache->registers_valid = 1;