x86/idt: Prepare for table based init

The IDT setup code is handled in several places. All of them use variants
of set_intr_gate() inlines. This can be done with a table based
initialization, which allows to reduce the inline zoo and puts all IDT
related code and information into a single place.

Add the infrastructure.

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/20170828064958.849877032@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/idt.c

@@ -5,8 +5,49 @@
  */
 #include <linux/interrupt.h>
 
+#include <asm/traps.h>
+#include <asm/proto.h>
 #include <asm/desc.h>
 
+struct idt_data {
+	unsigned int	vector;
+	unsigned int	segment;
+	struct idt_bits	bits;
+	const void	*addr;
+};
+
+#define DPL0		0x0
+#define DPL3		0x3
+
+#define DEFAULT_STACK	0
+
+#define G(_vector, _addr, _ist, _type, _dpl, _segment)	\
+	{						\
+		.vector		= _vector,		\
+		.bits.ist	= _ist,			\
+		.bits.type	= _type,		\
+		.bits.dpl	= _dpl,			\
+		.bits.p		= 1,			\
+		.addr		= _addr,		\
+		.segment	= _segment,		\
+	}
+
+/* Interrupt gate */
+#define INTG(_vector, _addr)				\
+	G(_vector, _addr, DEFAULT_STACK, GATE_INTERRUPT, DPL0, __KERNEL_CS)
+
+/* System interrupt gate */
+#define SYSG(_vector, _addr)				\
+	G(_vector, _addr, DEFAULT_STACK, GATE_INTERRUPT, DPL3, __KERNEL_CS)
+
+/* Interrupt gate with interrupt stack */
+#define ISTG(_vector, _addr, _ist)			\
+	G(_vector, _addr, _ist, GATE_INTERRUPT, DPL0, __KERNEL_CS)
+
+/* Task gate */
+#define TSKG(_vector, _gdt)				\
+	G(_vector, NULL, DEFAULT_STACK, GATE_TASK, DPL0, _gdt << 3)
+
 /* Must be page-aligned because the real IDT is used in a fixmap. */
 gate_desc idt_table[IDT_ENTRIES] __page_aligned_bss;
 
@@ -25,6 +66,32 @@ const struct desc_ptr debug_idt_descr = {
 };
 #endif
 
+static inline void idt_init_desc(gate_desc *gate, const struct idt_data *d)
+{
+	unsigned long addr = (unsigned long) d->addr;
+
+	gate->offset_low	= (u16) addr;
+	gate->segment		= (u16) d->segment;
+	gate->bits		= d->bits;
+	gate->offset_middle	= (u16) (addr >> 16);
+#ifdef CONFIG_X86_64
+	gate->offset_high	= (u32) (addr >> 32);
+	gate->reserved		= 0;
+#endif
+}
+
+static __init void
+idt_setup_from_table(gate_desc *idt, const struct idt_data *t, int size)
+{
+	gate_desc desc;
+
+	for (; size > 0; t++, size--) {
+		idt_init_desc(&desc, t);
+		set_bit(t->vector, used_vectors);
+		write_idt_entry(idt, t->vector, &desc);
+	}
+}
+
 /**
  * idt_setup_early_handler - Initializes the idt table with early handlers
  */