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x86: mpx: Give bndX registers actual names

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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;
	xsave_buf->bndreg[bndregno].upper_bound;

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@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: "Yu, Fenghua" <fenghua.yu@intel.com>
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20141031215820.5EA5E0EC@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Dave Hansen
2014-10-31 14:58:20 -07:00
committed by Thomas Gleixner
parent 6ba48ff46f
commit c04e051ccc
1 changed files with 4 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
arch/x86/include/asm/processor.h
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@@ -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)));