/*
* Basic support for controlling the 8259 Programmable Interrupt Controllers.
*
* Initially written by Michael Brown (mcb30).
*/
#include <etherboot.h>
#include "pic8259.h"
#include "realmode.h"
#ifdef DEBUG_IRQ
#define DBG(...) printf ( __VA_ARGS__ )
#else
#define DBG(...)
#endif
/* State of trivial IRQ handler */
irq_t trivial_irq_installed_on = IRQ_NONE;
static uint16_t trivial_irq_previous_trigger_count = 0;
/* The actual trivial IRQ handler
*
* Note: we depend on the C compiler not realising that we're putting
* variables in the ".text16" section and therefore not forcing them
* back to the ".data" section. I don't see any reason to expect this
* behaviour to change.
*
* These must *not* be the first variables to appear in this file; the
* first variable to appear gets the ".data" directive.
*/
RM_FRAGMENT(_trivial_irq_handler,
"pushw %bx\n\t"
"call 1f\n1:\tpopw %bx\n\t" /* PIC access to variables */
"incw %cs:(_trivial_irq_trigger_count-1b)(%bx)\n\t"
"popw %bx\n\t"
"iret\n\t"
"\n\t"
".globl _trivial_irq_trigger_count\n\t"
"_trivial_irq_trigger_count: .short 0\n\t"
"\n\t"
".globl _trivial_irq_chain_to\n\t"
"_trivial_irq_chain_to: .short 0,0\n\t"
"\n\t"
".globl _trivial_irq_chain\n\t"
"_trivial_irq_chain: .byte 0\n\t"
);
extern volatile uint16_t _trivial_irq_trigger_count;
extern segoff_t _trivial_irq_chain_to;
extern int8_t _trivial_irq_chain;
/* Current locations of trivial IRQ handler. These will change at
* runtime when relocation is used; the handler needs to be copied to
* base memory before being installed.
*/
void (*trivial_irq_handler)P((void)) = _trivial_irq_handler;
uint16_t volatile *trivial_irq_trigger_count = &_trivial_irq_trigger_count;
segoff_t *trivial_irq_chain_to = &_trivial_irq_chain_to;
uint8_t *trivial_irq_chain = &_trivial_irq_chain;
/* Install a handler for the specified IRQ. Address of previous
* handler will be stored in previous_handler. Enabled/disabled state
* of IRQ will be preserved across call, therefore if the handler does
* chaining, ensure that either (a) IRQ is disabled before call, or
* (b) previous_handler points directly to the place that the handler
* picks up its chain-to address.
*/
int install_irq_handler ( irq_t irq, segoff_t *handler,
uint8_t *previously_enabled,
segoff_t *previous_handler ) {
segoff_t *irq_vector = IRQ_VECTOR ( irq );
*previously_enabled = irq_enabled ( irq );
if ( irq > IRQ_MAX ) {
DBG ( "Invalid IRQ number %d\n" );
return 0;
}
previous_handler->segment = irq_vector->segment;
previous_handler->offset = irq_vector->offset;
if ( *previously_enabled ) disable_irq ( irq );
DBG ( "Installing handler at %hx:%hx for IRQ %d (vector 0000:%hx),"
" leaving %s\n",
handler->segment, handler->offset, irq, virt_to_phys(irq_vector),
( *previously_enabled ? "enabled" : "disabled" ) );
DBG ( "...(previous handler at %hx:%hx)\n",
previous_handler->segment, previous_handler->offset );
irq_vector->segment = handler->segment;
irq_vector->offset = handler->offset;
if ( *previously_enabled ) enable_irq ( irq );
return 1;
}
/* Remove handler for the specified IRQ. Routine checks that another
* handler has not been installed that chains to handler before
* uninstalling handler. Enabled/disabled state of the IRQ will be
* restored to that specified by previously_enabled.
*/
int remove_irq_handler ( irq_t irq, segoff_t *handler,
uint8_t *previously_enabled,
segoff_t *previous_handler ) {
segoff_t *irq_vector = IRQ_VECTOR ( irq );
if ( irq > IRQ_MAX ) {
DBG ( "Invalid IRQ number %d\n" );
return 0;
}
if ( ( irq_vector->segment != handler->segment ) ||
( irq_vector->offset != handler->offset ) ) {
DBG ( "Cannot remove handler for IRQ %d\n" );
return 0;
}
DBG ( "Removing handler for IRQ %d\n", irq );
disable_irq ( irq );
irq_vector->segment = previous_handler->segment;
irq_vector->offset = previous_handler->offset;
if ( *previously_enabled ) enable_irq ( irq );
return 1;
}
/* Install the trivial IRQ handler. This routine installs the
* handler, tests it and enables the IRQ.
*/
int install_trivial_irq_handler ( irq_t irq ) {
segoff_t trivial_irq_handler_segoff = SEGOFF(trivial_irq_handler);
if ( trivial_irq_installed_on != IRQ_NONE ) {
DBG ( "Can install trivial IRQ handler only once\n" );
return 0;
}
if ( SEGMENT(trivial_irq_handler) > 0xffff ) {
DBG ( "Trivial IRQ handler not in base memory\n" );
return 0;
}
DBG ( "Installing trivial IRQ handler on IRQ %d\n", irq );
if ( ! install_irq_handler ( irq, &trivial_irq_handler_segoff,
trivial_irq_chain,
trivial_irq_chain_to ) )
return 0;
trivial_irq_installed_on = irq;
DBG ( "Testing trivial IRQ handler\n" );
disable_irq ( irq );
*trivial_irq_trigger_count = 0;
trivial_irq_previous_trigger_count = 0;
fake_irq ( irq );
if ( ! trivial_irq_triggered ( irq ) ) {
DBG ( "Installation of trivial IRQ handler failed\n" );
remove_trivial_irq_handler ( irq );
return 0;
}
/* Send EOI just in case there was a leftover interrupt */
send_specific_eoi ( irq );
DBG ( "Trivial IRQ handler installed successfully\n" );
enable_irq ( irq );
return 1;
}
/* Remove the trivial IRQ handler.
*/
int remove_trivial_irq_handler ( irq_t irq ) {
segoff_t trivial_irq_handler_segoff = SEGOFF(trivial_irq_handler);
if ( trivial_irq_installed_on == IRQ_NONE ) return 1;
if ( irq != trivial_irq_installed_on ) {
DBG ( "Cannot uninstall trivial IRQ handler from IRQ %d; "
"is installed on IRQ %d\n", irq,
trivial_irq_installed_on );
return 0;
}
if ( ! remove_irq_handler ( irq, &trivial_irq_handler_segoff,
trivial_irq_chain,
trivial_irq_chain_to ) )
return 0;
if ( trivial_irq_triggered ( trivial_irq_installed_on ) ) {
DBG ( "Sending EOI for unwanted trivial IRQ\n" );
send_specific_eoi ( trivial_irq_installed_on );
}
trivial_irq_installed_on = IRQ_NONE;
return 1;
}
/* Safe method to detect whether or not trivial IRQ has been
* triggered. Using this call avoids potential race conditions. This
* call will return success only once per trigger.
*/
int trivial_irq_triggered ( irq_t irq ) {
uint16_t trivial_irq_this_trigger_count = *trivial_irq_trigger_count;
int triggered = ( trivial_irq_this_trigger_count -
trivial_irq_previous_trigger_count );
/* irq is not used at present, but we have it in the API for
* future-proofing; in case we want the facility to have
* multiple trivial IRQ handlers installed simultaneously.
*
* Avoid compiler warning about unused variable.
*/
if ( irq == IRQ_NONE ) {};
trivial_irq_previous_trigger_count = trivial_irq_this_trigger_count;
return triggered ? 1 : 0;
}
/* Copy trivial IRQ handler to a new location. Typically used to copy
* the handler into base memory; when relocation is being used we need
* to do this before installing the handler.
*
* Call with target=NULL in order to restore the handler to its
* original location.
*/
int copy_trivial_irq_handler ( void *target, size_t target_size ) {
irq_t currently_installed_on = trivial_irq_installed_on;
uint32_t offset = ( target == NULL ? 0 :
target - (void*)_trivial_irq_handler );
if (( target != NULL ) && ( target_size < TRIVIAL_IRQ_HANDLER_SIZE )) {
DBG ( "Insufficient space to copy trivial IRQ handler\n" );
return 0;
}
if ( currently_installed_on != IRQ_NONE ) {
DBG ("WARNING: relocating trivial IRQ handler while in use\n");
if ( ! remove_trivial_irq_handler ( currently_installed_on ) )
return 0;
}
/* Do the actual copy */
if ( target != NULL ) {
DBG ( "Copying trivial IRQ handler to %hx:%hx\n",
SEGMENT(target), OFFSET(target) );
memcpy ( target, _trivial_irq_handler,
TRIVIAL_IRQ_HANDLER_SIZE );
} else {
DBG ( "Restoring trivial IRQ handler to original location\n" );
}
/* Update all the pointers to structures within the handler */
trivial_irq_handler = ( void (*)P((void)) )
( (void*)_trivial_irq_handler + offset );
trivial_irq_trigger_count = (uint16_t*)
( (void*)&_trivial_irq_trigger_count + offset );
trivial_irq_chain_to = (segoff_t*)
( (void*)&_trivial_irq_chain_to + offset );
trivial_irq_chain = (uint8_t*)
( (void*)&_trivial_irq_chain + offset );
if ( currently_installed_on != IRQ_NONE ) {
if ( ! install_trivial_irq_handler ( currently_installed_on ) )
return 0;
}
return 1;
}
/* Send non-specific EOI(s). This seems to be inherently unsafe.
*/
void send_nonspecific_eoi ( irq_t irq ) {
DBG ( "Sending non-specific EOI for IRQ %d\n", irq );
if ( irq >= IRQ_PIC_CUTOFF ) {
outb ( ICR_EOI_NON_SPECIFIC, PIC2_ICR );
}
outb ( ICR_EOI_NON_SPECIFIC, PIC1_ICR );
}
/* Send specific EOI(s).
*/
void send_specific_eoi ( irq_t irq ) {
DBG ( "Sending specific EOI for IRQ %d\n", irq );
outb ( ICR_EOI_SPECIFIC | ICR_VALUE(irq), ICR_REG(irq) );
if ( irq >= IRQ_PIC_CUTOFF ) {
outb ( ICR_EOI_SPECIFIC | ICR_VALUE(CHAINED_IRQ),
ICR_REG(CHAINED_IRQ) );
}
}
/* Fake an IRQ
*/
void fake_irq ( irq_t irq ) {
struct {
uint16_t int_number;
} PACKED in_stack;
/* Convert IRQ to INT number:
*
* subb $0x08,%cl Invert bit 3, set bits 4-7 iff irq < 8
* xorb $0x70,%cl Invert bits 4-6
* andb $0x7f,%cl Clear bit 7
*
* No, it's not the most intuitive method, but I was proud to
* get it down to three lines of assembler when this routine
* was originally implemented in pcbios.S.
*/
in_stack.int_number = ( ( irq - 8 ) ^ 0x70 ) & 0x7f;
RM_FRAGMENT(rm_fake_irq,
"popw %ax\n\t" /* %ax = INT number */
"call 1f\n1:\tpop %bx\n\t"
"movb %al, %cs:(2f-1b+1)(%bx)\n\t" /* Overwrite INT number..*/
"\n2:\tint $0x00\n\t" /* ..in this instruction */
);
real_call ( rm_fake_irq, &in_stack, NULL );
}
/* Dump current 8259 status: enabled IRQs and handler addresses.
*/
#ifdef DEBUG_IRQ
void dump_irq_status ( void ) {
int irq = 0;
for ( irq = 0; irq < 16; irq++ ) {
if ( irq_enabled ( irq ) ) {
printf ( "IRQ%d enabled, ISR at %hx:%hx\n", irq,
IRQ_VECTOR(irq)->segment,
IRQ_VECTOR(irq)->offset );
}
}
}
#endif
