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>

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 726355c..1911310 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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)