[PATCH V5 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:

	* i387-tdep.h (i387_reset_bnd_regs): New.
	* i387-tdep.c (i387_reset_bnd_regs): New.
	* i386-tdep.c (i386_push_dummy_call): Call i387_reset_bnd_regs.
	* amd64-tdep (amd64_push_dummy_call): Call i387_reset_bnd_regs.

---
 gdb/amd64-tdep.c |  5 +++++
 gdb/i386-tdep.c  |  5 +++++
 gdb/i387-tdep.c  | 16 ++++++++++++++++
 gdb/i387-tdep.h  |  6 ++++++
 4 files changed, 32 insertions(+)

diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index a62efde..c1aca26 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -997,6 +997,11 @@ amd64_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
   enum bfd_endian byte_order = gdbarch_byte_order (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.  */
+  i387_reset_bnd_regs (gdbarch, regcache);
+
   /* 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..e8d41a3 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -2665,6 +2665,11 @@ i386_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
   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.  */
+  i387_reset_bnd_regs (gdbarch, regcache);
+
   /* 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.  */
diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c
index f7a3b55..9bb3177 100644
--- a/gdb/i387-tdep.c
+++ b/gdb/i387-tdep.c
@@ -1772,3 +1772,19 @@ i387_return_value (struct gdbarch *gdbarch, struct regcache *regcache)
   regcache_raw_write_unsigned (regcache, I387_FTAG_REGNUM (tdep), 0x3fff);
 
 }
+
+void
+i387_reset_bnd_regs (struct gdbarch *gdbarch, struct regcache *regcache)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+  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);
+    }
+}
diff --git a/gdb/i387-tdep.h b/gdb/i387-tdep.h
index b4dc2b7..3ac4b4d 100644
--- a/gdb/i387-tdep.h
+++ b/gdb/i387-tdep.h
@@ -156,4 +156,10 @@ extern void i387_collect_xsave (const struct regcache *regcache,
 extern void i387_return_value (struct gdbarch *gdbarch,
 			       struct regcache *regcache);
 
+/* Set all bnd registers to the INIT state. INIT state means
+   all memory range can be accessed.  */
+
+extern void i387_reset_bnd_regs (struct gdbarch *gdbarch,
+			         struct regcache *regcache);
+
 #endif /* i387-tdep.h */
-- 
2.1.4