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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug testsuite/26991] FAIL: gdb.arch/i386-mpx-call.exp: upper_bnd0:
 continue to a bnd violation
Date: Wed, 02 Dec 2020 13:27:49 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D26991

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
As for the remaining failure.

Things are made complicated by the fact that bnd0.lbound and bnd0.ubound are
represented as 32-bit in -m32, while in the hardware they're actually 64-bi=
t.

This is reflected in the types:
...
(gdb) ptype $bnd0
type =3D struct builtin_type_bound128 {
    void *lbound;
    void *ubound;
}
(gdb) ptype $bnd0raw
type =3D struct br128 {
    uint64_t lbound;
    uint64_t ubound_raw;
}
...

So, the interesting thing is always to print the raw value to see what's
actually written in the hw register.

So, before the FAIL we have:
...
(gdb) p /x $bnd0.lbound =3D $bnd0.ubound^M
$19 =3D 0xffffffff^M
(gdb) p /x $bnd0.ubound =3D 0^M
$20 =3D 0x0^M
(gdb) p /x $bnd0raw^M
$21 =3D {lbound =3D 0xffffffff, ubound_raw =3D 0xffffffffffffffff}^M
...

Now comparing that with the info found here (
https://www.felixcloutier.com/x86/bndmk ):
...
BND.LB =E2=86=90 SRCMEM.base;
IF 64-bit mode Then
    BND.UB =E2=86=90 NOT(LEA.64_bits(SRCMEM));
ELSE
    BND.UB =E2=86=90 Zero_Extend.64_bits(NOT(LEA.32_bits(SRCMEM)));
FI;
...
we can see that the value written into ubound_raw is not congruent with how
bndmk would write it.

Using this tentative patch:
...
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 00de4e1ccb..2ea28c68bd 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -3527,6 +3527,8 @@ i386_pseudo_register_write=20
                              raw_buf);

          upper =3D ~upper;
+         if (size =3D=3D 4)
+           upper =3D upper & 0xffffffff;

          /* Set register bits.  */
          memcpy (raw_buf, &lower, 8);
...
fixes that, but not the FAIL.

--=20
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