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