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[librm] Allow interrupts in protected mode

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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>
This commit is contained in:
Michael Brown
2014-04-28 20:17:15 +01:00
parent 4413ab4f5a
commit 23b671daf4
9 changed files with 322 additions and 135 deletions
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83
src/arch/i386/transitions/librm_mgmt.c
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@@ -9,19 +9,35 @@ FILE_LICENCE ( GPL2_OR_LATER );
#include <stdint.h>
#include <realmode.h>
#include <pic8259.h>
/*
* This file provides functions for managing librm.
*
*/
/** The interrupt wrapper */
extern char interrupt_wrapper[];
/** The interrupt vectors */
static struct interrupt_vector intr_vec[ IRQ_MAX + 1 ];
/** The interrupt descriptor table */
struct interrupt_descriptor idt[NUM_INT] __attribute__ (( aligned ( 16 ) ));
/** The interrupt descriptor table register */
struct idtr __data16 ( idtr ) = {
.limit = ( sizeof ( idt ) - 1 ),
};
#define idtr __use_data16 ( idtr )
/**
* Allocate space on the real-mode stack and copy data there from a
* user buffer
*
* @v data User buffer
* @v size Size of stack data
* @ret sp New value of real-mode stack pointer
* @v data User buffer
* @v size Size of stack data
* @ret sp New value of real-mode stack pointer
*/
uint16_t copy_user_to_rm_stack ( userptr_t data, size_t size ) {
userptr_t rm_stack;
@@ -35,8 +51,8 @@ uint16_t copy_user_to_rm_stack ( userptr_t data, size_t size ) {
* Deallocate space on the real-mode stack, optionally copying back
* data to a user buffer.
*
* @v data User buffer
* @v size Size of stack data
* @v data User buffer
* @v size Size of stack data
*/
void remove_user_from_rm_stack ( userptr_t data, size_t size ) {
if ( data ) {
@@ -46,6 +62,63 @@ void remove_user_from_rm_stack ( userptr_t data, size_t size ) {
rm_sp += size;
};
/**
* Set interrupt vector
*
* @v intr Interrupt number
* @v vector Interrupt vector, or NULL to disable
*/
void set_interrupt_vector ( unsigned int intr, void *vector ) {
struct interrupt_descriptor *idte;
idte = &idt[intr];
idte->segment = VIRTUAL_CS;
idte->attr = ( vector ? ( IDTE_PRESENT | IDTE_TYPE_IRQ32 ) : 0 );
idte->low = ( ( ( uint32_t ) vector ) & 0xffff );
idte->high = ( ( ( uint32_t ) vector ) >> 16 );
}
/**
* Initialise interrupt descriptor table
*
*/
void init_idt ( void ) {
struct interrupt_vector *vec;
unsigned int irq;
unsigned int intr;
/* Initialise the interrupt descriptor table and interrupt vectors */
for ( irq = 0 ; irq <= IRQ_MAX ; irq++ ) {
intr = IRQ_INT ( irq );
vec = &intr_vec[irq];
vec->pushal = PUSHAL_INSN;
vec->movb = MOVB_INSN;
vec->intr = intr;
vec->jmp = JMP_INSN;
vec->offset = ( ( uint32_t ) interrupt_wrapper -
( uint32_t ) vec->next );
set_interrupt_vector ( intr, vec );
}
/* Initialise the interrupt descriptor table register */
idtr.base = virt_to_phys ( idt );
}
/**
* Interrupt handler
*
* @v irq Interrupt number
*/
void __attribute__ (( cdecl, regparm ( 1 ) )) interrupt ( int irq ) {
uint32_t discard_eax;
/* Reissue interrupt in real mode */
__asm__ __volatile__ ( REAL_CODE ( "movb %%al, %%cs:(1f + 1)\n\t"
"\n1:\n\t"
"int $0x00\n\t" )
: "=a" ( discard_eax ) : "0" ( irq ) );
}
PROVIDE_UACCESS_INLINE ( librm, phys_to_user );
PROVIDE_UACCESS_INLINE ( librm, user_to_phys );
PROVIDE_UACCESS_INLINE ( librm, virt_to_user );