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

[Luis Machado <lgustavo at codesourcery dot com>]

On 03/02/2016 01:21 PM, Walfred Tedeschi wrote:
> 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.  */

Not sure if it was suggested previously in earlier versions of this 
series (i could not find it), but wouldn't it make sense to have that 
code moved to a new function in, say, i387-tdep.c? Then we wouldn't need 
to duplicate the code as above.