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Subject[PATCH 10/15] x86, fpu: rework MPX 'xstate' types
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From: Dave Hansen <dave.hansen@linux.intel.com>

MPX includes two separate "extended state components". There is
no real need to have an 'mpx_struct' because we never really
manage the states together.

We also separate out the actual data in 'mpx_bndcsr_state' from
the padding. We will shortly be checking the state sizes against
our structures and need them to match. For consistency, we also
ensure to prefix these types with 'mpx_'.

Lastly, we add some comments to mirror some of the descriptions
in the Intel documents (SDM) of the various state components.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org
---

b/arch/x86/include/asm/fpu/types.h | 33 +++++++++++++++++++++++++--------
b/arch/x86/include/asm/trace/mpx.h | 7 ++++---
b/arch/x86/kernel/traps.c | 2 +-
b/arch/x86/mm/mpx.c | 9 +++++----
4 files changed, 35 insertions(+), 16 deletions(-)

diff -puN arch/x86/include/asm/fpu/types.h~x86-fpu-rework-mpx-types arch/x86/include/asm/fpu/types.h
--- a/arch/x86/include/asm/fpu/types.h~x86-fpu-rework-mpx-types 2015-08-31 15:17:35.427929527 -0700
+++ b/arch/x86/include/asm/fpu/types.h 2015-08-31 15:17:35.436929938 -0700
@@ -141,20 +141,37 @@ struct ymmh_struct {
};

/* Intel MPX support: */
-struct bndreg {
+
+struct mpx_bndreg {
u64 lower_bound;
u64 upper_bound;
} __packed;
+/*
+ * State component 3 is used for the 4 128-bit bounds registers
+ */
+struct mpx_bndreg_state {
+ struct mpx_bndreg bndreg[4];
+} __packed;

-struct bndcsr {
- u64 bndcfgu;
- u64 bndstatus;
+/*
+ * State component 4 is used for the 64-bit user-mode MPX
+ * configuration register BNDCFGU and the 64-bit MPX status
+ * register BNDSTATUS. We call the pair "BNDCSR".
+ */
+struct mpx_bndcsr {
+ u64 bndcfgu;
+ u64 bndstatus;
} __packed;

-struct mpx_struct {
- struct bndreg bndreg[4];
- struct bndcsr bndcsr;
-};
+/*
+ * The BNDCSR state is padded out to be 64-bytes in size.
+ */
+struct mpx_bndcsr_state {
+ union {
+ struct mpx_bndcsr bndcsr;
+ u8 pad_to_64_bytes[64];
+ };
+} __packed;

struct xstate_header {
u64 xfeatures;
diff -puN arch/x86/include/asm/trace/mpx.h~x86-fpu-rework-mpx-types arch/x86/include/asm/trace/mpx.h
--- a/arch/x86/include/asm/trace/mpx.h~x86-fpu-rework-mpx-types 2015-08-31 15:17:35.429929618 -0700
+++ b/arch/x86/include/asm/trace/mpx.h 2015-08-31 15:17:35.436929938 -0700
@@ -11,7 +11,7 @@
TRACE_EVENT(mpx_bounds_register_exception,

TP_PROTO(void *addr_referenced,
- const struct bndreg *bndreg),
+ const struct mpx_bndreg *bndreg),
TP_ARGS(addr_referenced, bndreg),

TP_STRUCT__entry(
@@ -44,7 +44,7 @@ TRACE_EVENT(mpx_bounds_register_exceptio

TRACE_EVENT(bounds_exception_mpx,

- TP_PROTO(const struct bndcsr *bndcsr),
+ TP_PROTO(const struct mpx_bndcsr *bndcsr),
TP_ARGS(bndcsr),

TP_STRUCT__entry(
@@ -116,7 +116,8 @@ TRACE_EVENT(mpx_new_bounds_table,
/*
* This gets used outside of MPX-specific code, so we need a stub.
*/
-static inline void trace_bounds_exception_mpx(const struct bndcsr *bndcsr)
+static inline
+void trace_bounds_exception_mpx(const struct mpx_bndcsr *bndcsr)
{
}

diff -puN arch/x86/kernel/traps.c~x86-fpu-rework-mpx-types arch/x86/kernel/traps.c
--- a/arch/x86/kernel/traps.c~x86-fpu-rework-mpx-types 2015-08-31 15:17:35.431929709 -0700
+++ b/arch/x86/kernel/traps.c 2015-08-31 15:17:35.437929984 -0700
@@ -372,7 +372,7 @@ dotraplinkage void do_double_fault(struc
dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
{
enum ctx_state prev_state;
- const struct bndcsr *bndcsr;
+ const struct mpx_bndcsr *bndcsr;
siginfo_t *info;

prev_state = exception_enter();
diff -puN arch/x86/mm/mpx.c~x86-fpu-rework-mpx-types arch/x86/mm/mpx.c
--- a/arch/x86/mm/mpx.c~x86-fpu-rework-mpx-types 2015-08-31 15:17:35.432929755 -0700
+++ b/arch/x86/mm/mpx.c 2015-08-31 15:17:35.437929984 -0700
@@ -274,7 +274,8 @@ bad_opcode:
*/
siginfo_t *mpx_generate_siginfo(struct pt_regs *regs)
{
- const struct bndreg *bndregs, *bndreg;
+ const struct mpx_bndreg_state *bndregs;
+ const struct mpx_bndreg *bndreg;
siginfo_t *info = NULL;
struct insn insn;
uint8_t bndregno;
@@ -301,7 +302,7 @@ siginfo_t *mpx_generate_siginfo(struct p
goto err_out;
}
/* now go select the individual register in the set of 4 */
- bndreg = &bndregs[bndregno];
+ bndreg = &bndregs->bndreg[bndregno];

info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info) {
@@ -343,7 +344,7 @@ err_out:

static __user void *mpx_get_bounds_dir(void)
{
- const struct bndcsr *bndcsr;
+ const struct mpx_bndcsr *bndcsr;

if (!cpu_feature_enabled(X86_FEATURE_MPX))
return MPX_INVALID_BOUNDS_DIR;
@@ -526,7 +527,7 @@ out_unmap:
static int do_mpx_bt_fault(void)
{
unsigned long bd_entry, bd_base;
- const struct bndcsr *bndcsr;
+ const struct mpx_bndcsr *bndcsr;
struct mm_struct *mm = current->mm;

bndcsr = get_xsave_field_ptr(XFEATURE_MASK_BNDCSR);
_

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