From 23b671daf490acaec6fdad55f2bfa44021200a63 Mon Sep 17 00:00:00 2001
From: Michael Brown
Date: Mon, 28 Apr 2014 20:17:15 +0100
Subject: [librm] Allow interrupts in protected mode

When running in a virtual machine, switching to real mode may be
expensive.  Allow interrupts to be enabled while in protected mode and
reflected down to the real-mode interrupt handlers.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/arch/i386/include/gdbmach.h | 10 +++++++
 src/arch/i386/include/librm.h   | 65 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)

(limited to 'src/arch/i386/include')

diff --git a/src/arch/i386/include/gdbmach.h b/src/arch/i386/include/gdbmach.h
index 794dab193..416ae341a 100644
--- a/src/arch/i386/include/gdbmach.h
+++ b/src/arch/i386/include/gdbmach.h
@@ -46,6 +46,14 @@ enum {
 	GDBMACH_AWATCH,
 };
 
+/* Interrupt vectors */
+extern void gdbmach_nocode_sigfpe ( void );
+extern void gdbmach_nocode_sigtrap ( void );
+extern void gdbmach_nocode_sigstkflt ( void );
+extern void gdbmach_nocode_sigill ( void );
+extern void gdbmach_withcode_sigbus ( void );
+extern void gdbmach_withcode_sigsegv ( void );
+
 static inline void gdbmach_set_pc ( gdbreg_t *regs, gdbreg_t pc ) {
 	regs [ GDBMACH_EIP ] = pc;
 }
@@ -61,4 +69,6 @@ static inline void gdbmach_breakpoint ( void ) {
 
 extern int gdbmach_set_breakpoint ( int type, unsigned long addr, size_t len, int enable );
 
+extern void gdbmach_init ( void );
+
 #endif /* GDBMACH_H */
diff --git a/src/arch/i386/include/librm.h b/src/arch/i386/include/librm.h
index fc5598eba..4a4e61aa1 100644
--- a/src/arch/i386/include/librm.h
+++ b/src/arch/i386/include/librm.h
@@ -209,6 +209,71 @@ extern void remove_user_from_rm_stack ( userptr_t data, size_t size );
 	asm_code_str					\
 	"call _phys_to_virt\n\t"
 
+/** Number of interrupts */
+#define NUM_INT 256
+
+/** An interrupt descriptor table register */
+struct idtr {
+	/** Limit */
+	uint16_t limit;
+	/** Base */
+	uint32_t base;
+} __attribute__ (( packed ));
+
+/** An interrupt descriptor table entry */
+struct interrupt_descriptor {
+	/** Low 16 bits of address */
+	uint16_t low;
+	/** Code segment */
+	uint16_t segment;
+	/** Unused */
+	uint8_t unused;
+	/** Type and attributes */
+	uint8_t attr;
+	/** High 16 bits of address */
+	uint16_t high;
+} __attribute__ (( packed ));
+
+/** Interrupt descriptor is present */
+#define IDTE_PRESENT 0x80
+
+/** Interrupt descriptor 32-bit interrupt gate type */
+#define IDTE_TYPE_IRQ32 0x0e
+
+/** An interrupt vector
+ *
+ * Each interrupt vector comprises an eight-byte fragment of code:
+ *
+ *   60			pushal
+ *   b0 xx		movb $INT, %al
+ *   e9 xx xx xx xx	jmp interrupt_wrapper
+ */
+struct interrupt_vector {
+	/** "pushal" instruction */
+	uint8_t pushal;
+	/** "movb" instruction */
+	uint8_t movb;
+	/** Interrupt number */
+	uint8_t intr;
+	/** "jmp" instruction */
+	uint8_t jmp;
+	/** Interrupt wrapper address offset */
+	uint32_t offset;
+	/** Next instruction after jump */
+	uint8_t next[0];
+} __attribute__ (( packed ));
+
+/** "pushal" instruction */
+#define PUSHAL_INSN 0x60
+
+/** "movb" instruction */
+#define MOVB_INSN 0xb0
+
+/** "jmp" instruction */
+#define JMP_INSN 0xe9
+
+extern void set_interrupt_vector ( unsigned int intr, void *vector );
+
 #endif /* ASSEMBLY */
 
 #endif /* LIBRM_H */
-- 
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