[tip:x86/apic] x86/gdt: Use bitfields for initialization

tip-bot for Thomas Gleixner
2017-08-29T11:20:09Z

Commit-ID: 38e9e81f4c81c75799b002d5811de7241b307676
Gitweb: http://git.kernel.org/tip/38e9e81f4c81c75799b002d5811de7241b307676
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Mon, 28 Aug 2017 08:47:41 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 29 Aug 2017 12:07:25 +0200

x86/gdt: Use bitfields for initialization

The GDT entry related code uses two ways to access entries via
union fields:

- bitfields

- macros which initialize the two 16-bit parts of the entry
by magic shift and mask operations.

Clean it up and only use the bitfields to initialize and access entries.

( The old access patterns were partly done due to GCC optimizing bitfield
accesses in a horrible way - that's mostly fixed these days and clarity
of code in such low level accessors is very important. )

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064958.197673367@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/vdso/vma.c | 2 +-
arch/x86/include/asm/desc.h | 26 +++++++++++++++---------
arch/x86/include/asm/desc_defs.h | 44 ++++++++++++++++++----------------------
arch/x86/math-emu/fpu_system.h | 2 +-
4 files changed, 38 insertions(+), 36 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 726355c..1911310 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -351,7 +351,7 @@ static void vgetcpu_cpu_init(void *arg)
* and 8 bits for the node)
*/
d.limit0 = cpu | ((node & 0xf) << 12);
- d.limit = node >> 4;
+ d.limit1 = node >> 4;
d.type = 5; /* RO data, expand down, accessed */
d.dpl = 3; /* Visible to user code */
d.s = 1; /* Not a system segment */
diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 0731064..2090cd2 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -23,7 +23,7 @@ static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *in
desc->s = 1;
desc->dpl = 0x3;
desc->p = info->seg_not_present ^ 1;
- desc->limit = (info->limit & 0xf0000) >> 16;
+ desc->limit1 = (info->limit & 0xf0000) >> 16;
desc->avl = info->useable;
desc->d = info->seg_32bit;
desc->g = info->limit_in_pages;
@@ -170,14 +170,20 @@ static inline void pack_descriptor(struct desc_struct *desc, unsigned long base,
unsigned long limit, unsigned char type,
unsigned char flags)
{
- desc->a = ((base & 0xffff) << 16) | (limit & 0xffff);
- desc->b = (base & 0xff000000) | ((base & 0xff0000) >> 16) |
- (limit & 0x000f0000) | ((type & 0xff) << 8) |
- ((flags & 0xf) << 20);
- desc->p = 1;
+ desc->limit0 = (u16) limit;
+ desc->base0 = (u16) base;
+ desc->base1 = (base >> 16) & 0xFF;
+ desc->type = type & 0x0F;
+ desc->s = 0;
+ desc->dpl = 0;
+ desc->p = 1;
+ desc->limit1 = (limit >> 16) & 0xF;
+ desc->avl = (flags >> 0) & 0x01;
+ desc->l = (flags >> 1) & 0x01;
+ desc->d = (flags >> 2) & 0x01;
+ desc->g = (flags >> 3) & 0x01;
}

-
static inline void set_tssldt_descriptor(void *d, unsigned long addr,
unsigned type, unsigned size)
{
@@ -195,7 +201,7 @@ static inline void set_tssldt_descriptor(void *d, unsigned long addr,
desc->base2 = (addr >> 24) & 0xFF;
desc->base3 = (u32) (addr >> 32);
#else
- pack_descriptor((struct desc_struct *)d, addr, size, 0x80 | type, 0);
+ pack_descriptor((struct desc_struct *)d, addr, size, type, 0);
#endif
}

@@ -395,13 +401,13 @@ static inline void set_desc_base(struct desc_struct *desc, unsigned long base)

static inline unsigned long get_desc_limit(const struct desc_struct *desc)
{
- return desc->limit0 | (desc->limit << 16);
+ return desc->limit0 | (desc->limit1 << 16);
}

static inline void set_desc_limit(struct desc_struct *desc, unsigned long limit)
{
desc->limit0 = limit & 0xffff;
- desc->limit = (limit >> 16) & 0xf;
+ desc->limit1 = (limit >> 16) & 0xf;
}

#ifdef CONFIG_X86_64
diff --git a/arch/x86/include/asm/desc_defs.h b/arch/x86/include/asm/desc_defs.h
index d684bee..1b9494e 100644
--- a/arch/x86/include/asm/desc_defs.h
+++ b/arch/x86/include/asm/desc_defs.h
@@ -11,34 +11,30 @@

#include <linux/types.h>

-/*
- * FIXME: Accessing the desc_struct through its fields is more elegant,
- * and should be the one valid thing to do. However, a lot of open code
- * still touches the a and b accessors, and doing this allow us to do it
- * incrementally. We keep the signature as a struct, rather than a union,
- * so we can get rid of it transparently in the future -- glommer
- */
/* 8 byte segment descriptor */
struct desc_struct {
- union {
- struct {
- unsigned int a;
- unsigned int b;
- };
- struct {
- u16 limit0;
- u16 base0;
- unsigned base1: 8, type: 4, s: 1, dpl: 2, p: 1;
- unsigned limit: 4, avl: 1, l: 1, d: 1, g: 1, base2: 8;
- };
- };
+ u16 limit0;
+ u16 base0;
+ u16 base1: 8, type: 4, s: 1, dpl: 2, p: 1;
+ u16 limit1: 4, avl: 1, l: 1, d: 1, g: 1, base2: 8;
} __attribute__((packed));

-#define GDT_ENTRY_INIT(flags, base, limit) { { { \
- .a = ((limit) & 0xffff) | (((base) & 0xffff) << 16), \
- .b = (((base) & 0xff0000) >> 16) | (((flags) & 0xf0ff) << 8) | \
- ((limit) & 0xf0000) | ((base) & 0xff000000), \
- } } }
+#define GDT_ENTRY_INIT(flags, base, limit) \
+ { \
+ .limit0 = (u16) (limit), \
+ .limit1 = ((limit) >> 16) & 0x0F, \
+ .base0 = (u16) (base), \
+ .base1 = ((base) >> 16) & 0xFF, \
+ .base2 = ((base) >> 24) & 0xFF, \
+ .type = (flags & 0x0f), \
+ .s = (flags >> 4) & 0x01, \
+ .dpl = (flags >> 5) & 0x03, \
+ .p = (flags >> 7) & 0x01, \
+ .avl = (flags >> 12) & 0x01, \
+ .l = (flags >> 13) & 0x01, \
+ .d = (flags >> 14) & 0x01, \
+ .g = (flags >> 15) & 0x01, \
+ }

enum {
GATE_INTERRUPT = 0xE,
diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index 2319a25..699f329 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -49,7 +49,7 @@ static inline unsigned long seg_get_base(struct desc_struct *d)

static inline unsigned long seg_get_limit(struct desc_struct *d)
{
- return ((unsigned long)d->limit << 16) | d->limit0;
+ return ((unsigned long)d->limit1 << 16) | d->limit0;
}

static inline unsigned long seg_get_granularity(struct desc_struct *d)