[tip:x86/mpx] x86: mpx: Give bndX registers actual names

From: tip-bot for Dave Hansen
Date: Mon Nov 17 2014 - 19:05:18 EST

Commit-ID: c04e051cccd2446d9ca373628d14b7e732462f5d
Gitweb: http://git.kernel.org/tip/c04e051cccd2446d9ca373628d14b7e732462f5d
Author: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 31 Oct 2014 14:58:20 -0700
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 18 Nov 2014 00:58:52 +0100

x86: mpx: Give bndX registers actual names

Consider the bndX MPX registers. There 4 registers each
containing a 64-bit lower and a 64-bit upper bound. That's 8*64
bits and we declare it thusly:

struct bndregs_struct {
u64 bndregs[8];

Let's say you want to read the upper bound from the MPX register
bnd2 out of the xsave buf. You do:

bndregno = 2;
upper_bound = xsave_buf->bndregs.bndregs[2*bndregno+1];

That kinda sucks. Every time you access it, you need to know:
1. Each bndX register is two entries wide in "bndregs"
2. The lower comes first followed by upper. We do the +1 to get
upper vs. lower.

This replaces the old definition. You can now access them
indexed by the register number directly, and with a meaningful
name for the lower and upper bound:

bndregno = 2;

It's now *VERY* clear that there are 4 registers. The programmer
now doesn't have to care what order the lower and upper bounds
are in, and it's harder to get it wrong.

[ tglx: Changed ub/lb to upper_bound/lower_bound and renamed struct
bndreg_struct to struct bndreg ]

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: "H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx>
Cc: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
Cc: "Yu, Fenghua" <fenghua.yu@xxxxxxxxx>
Cc: Dave Hansen <dave@xxxxxxxx>
Link: http://lkml.kernel.org/r/20141031215820.5EA5E0EC@xxxxxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
arch/x86/include/asm/processor.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index eb71ec7..0f2263a 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -374,8 +374,9 @@ struct lwp_struct {
u8 reserved[128];

-struct bndregs_struct {
- u64 bndregs[8];
+struct bndreg {
+ u64 lower_bound;
+ u64 upper_bound;
} __packed;

struct bndcsr_struct {
@@ -394,7 +395,7 @@ struct xsave_struct {
struct xsave_hdr_struct xsave_hdr;
struct ymmh_struct ymmh;
struct lwp_struct lwp;
- struct bndregs_struct bndregs;
+ struct bndreg bndreg[4];
struct bndcsr_struct bndcsr;
/* new processor state extensions will go here */
} __attribute__ ((packed, aligned (64)));
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