[PATCH V4 1/2] Initialize bnd register before performing inferior calls.

[Walfred Tedeschi <walfred.tedeschi@intel.com>]

BND registers should be initialized before performing an inferior call
to avoid undesired bound violations.

2016-02-03  Walfred Tedeschi <walfred.tedeschi@intel.com>

gdb/ChangeLog:

	* i386-tdep.c (i386_push_dummy_call): Initialize bnd registers.
	* amd64-tdep (amd64_push_dummy_call): Initialize bnd registers.

---
 gdb/amd64-tdep.c | 15 +++++++++++++++
 gdb/i386-tdep.c  | 15 +++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index a62efde..0e4e89b 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -995,8 +995,23 @@ amd64_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
 		       int struct_return, CORE_ADDR struct_addr)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   gdb_byte buf[8];
 
+  /* When MPX is enabled, all bnd registers have to be initialized
+     before the call.  This avoids an undesired bound violation
+     during the function's execution.  */
+
+  if (I387_BND0R_REGNUM (tdep) > 0)
+    {
+      gdb_byte bnd_buf[16];
+      int i;
+
+      memset (bnd_buf, 0, 16);
+      for (i = 0; i < I387_BND0R_REGNUM (tdep); i++)
+	regcache_raw_write (regcache, I387_BND0R_REGNUM (tdep) + i, bnd_buf);
+    }
+
   /* Pass arguments.  */
   sp = amd64_push_arguments (regcache, nargs, args, sp, struct_return);
 
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 4c66edf..8c3576c 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -2660,11 +2660,26 @@ i386_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
 		      CORE_ADDR struct_addr)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   gdb_byte buf[4];
   int i;
   int write_pass;
   int args_space = 0;
 
+  /* When MPX is enabled, all bnd registers have to be initialized
+     before the call.  This avoids an undesired bound violation
+     during the function's execution.  */
+
+  if (I387_BND0R_REGNUM (tdep) > 0)
+    {
+      gdb_byte bnd_buf[16];
+      int i;
+
+      memset (bnd_buf, 0, 16);
+      for (i = 0; i < I387_BND0R_REGNUM (tdep); i++)
+	regcache_raw_write (regcache, I387_BND0R_REGNUM (tdep) + i, bnd_buf);
+    }
+
   /* Determine the total space required for arguments and struct
      return address in a first pass (allowing for 16-byte-aligned
      arguments), then push arguments in a second pass.  */
-- 
2.1.4