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/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,
