1 files changed, 234 insertions, 0 deletions
diff --git a/src/VBox/Devices/PC/ipxe/src/interface/efi/efi_timer.c b/src/VBox/Devices/PC/ipxe/src/interface/efi/efi_timer.c
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+++ b/src/VBox/Devices/PC/ipxe/src/interface/efi/efi_timer.c
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+/*
+ * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <ipxe/timer.h>
+#include <ipxe/init.h>
+#include <ipxe/efi/efi.h>
+
+/** @file
+ *
+ * iPXE timer API for EFI
+ *
+ */
+
+/**
+ * Number of jiffies per second
+ *
+ * This is a policy decision.
+ */
+#define EFI_JIFFIES_PER_SEC 32
+
+/** Current tick count */
+static unsigned long efi_jiffies;
+
+/** Timer tick event */
+static EFI_EVENT efi_tick_event;
+
+/** Colour for debug messages */
+#define colour &efi_jiffies
+
+/**
+ * Delay for a fixed number of microseconds
+ *
+ * @v usecs		Number of microseconds for which to delay
+ */
+static void efi_udelay ( unsigned long usecs ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_STATUS efirc;
+	int rc;
+
+	if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( colour, "EFI could not delay for %ldus: %s\n",
+		       usecs, strerror ( rc ) );
+		/* Probably screwed */
+	}
+}
+
+/**
+ * Get current system time in ticks
+ *
+ * @ret ticks		Current time, in ticks
+ */
+static unsigned long efi_currticks ( void ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+
+	/* UEFI manages to ingeniously combine the worst aspects of
+	 * both polling and interrupt-driven designs.  There is no way
+	 * to support proper interrupt-driven operation, since there
+	 * is no way to hook in an interrupt service routine.  A
+	 * mockery of interrupts is provided by UEFI timers, which
+	 * trigger at a preset rate and can fire at any time.
+	 *
+	 * We therefore have all of the downsides of a polling design
+	 * (inefficiency and inability to sleep until something
+	 * interesting happens) combined with all of the downsides of
+	 * an interrupt-driven design (the complexity of code that
+	 * could be preempted at any time).
+	 *
+	 * The UEFI specification expects us to litter the entire
+	 * codebase with calls to RaiseTPL() as needed for sections of
+	 * code that are not reentrant.  Since this doesn't actually
+	 * gain us any substantive benefits (since even with such
+	 * calls we would still be suffering from the limitations of a
+	 * polling design), we instead choose to run at TPL_CALLBACK
+	 * almost all of the time, dropping to a lower TPL to allow
+	 * timer ticks to occur.
+	 *
+	 * We record the external TPL at the point of entry into iPXE,
+	 * and drop back only as far as this external TPL.  This
+	 * avoids the unexpected behaviour that may arise from having
+	 * iPXE temporarily drop to TPL_APPLICATION in the middle of
+	 * an entry point invoked at TPL_CALLBACK.  The side effect is
+	 * that iPXE's view of the system time is effectively frozen
+	 * for the duration of any call made in to iPXE at
+	 * TPL_CALLBACK or higher.
+	 *
+	 *
+	 * For added excitement, UEFI provides no clean way for device
+	 * drivers to shut down in preparation for handover to a
+	 * booted operating system.  The platform firmware simply
+	 * doesn't bother to call the drivers' Stop() methods.
+	 * Instead, all non-trivial drivers must register an
+	 * EVT_SIGNAL_EXIT_BOOT_SERVICES event to be signalled when
+	 * ExitBootServices() is called, and clean up without any
+	 * reference to the EFI driver model.
+	 *
+	 * Unfortunately, all timers silently stop working when
+	 * ExitBootServices() is called.  Even more unfortunately, and
+	 * for no discernible reason, this happens before any
+	 * EVT_SIGNAL_EXIT_BOOT_SERVICES events are signalled.  The
+	 * net effect of this entertaining design choice is that any
+	 * timeout loops on the shutdown path (e.g. for gracefully
+	 * closing outstanding TCP connections) may wait indefinitely.
+	 *
+	 * There is no way to report failure from currticks(), since
+	 * the API lazily assumes that the host system continues to
+	 * travel through time in the usual direction.  Work around
+	 * EFI's violation of this assumption by falling back to a
+	 * simple free-running monotonic counter during shutdown.
+	 */
+	if ( efi_shutdown_in_progress ) {
+		efi_jiffies++;
+	} else {
+		bs->RestoreTPL ( efi_external_tpl );
+		bs->RaiseTPL ( TPL_CALLBACK );
+	}
+
+	return ( efi_jiffies * ( TICKS_PER_SEC / EFI_JIFFIES_PER_SEC ) );
+}
+
+/**
+ * Timer tick
+ *
+ * @v event		Timer tick event
+ * @v context		Event context
+ */
+static EFIAPI void efi_tick ( EFI_EVENT event __unused,
+			      void *context __unused ) {
+
+	/* Increment tick count */
+	efi_jiffies++;
+}
+
+/**
+ * Start timer tick
+ *
+ */
+static void efi_tick_startup ( void ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Create timer tick event */
+	if ( ( efirc = bs->CreateEvent ( ( EVT_TIMER | EVT_NOTIFY_SIGNAL ),
+					 TPL_CALLBACK, efi_tick, NULL,
+					 &efi_tick_event ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( colour, "EFI could not create timer tick: %s\n",
+		       strerror ( rc ) );
+		/* Nothing we can do about it */
+		return;
+	}
+
+	/* Start timer tick */
+	if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerPeriodic,
+				      ( 10000000 / EFI_JIFFIES_PER_SEC ) ))!=0){
+		rc = -EEFI ( efirc );
+		DBGC ( colour, "EFI could not start timer tick: %s\n",
+		       strerror ( rc ) );
+		/* Nothing we can do about it */
+		return;
+	}
+	DBGC ( colour, "EFI timer started at %d ticks per second\n",
+	       EFI_JIFFIES_PER_SEC );
+}
+
+/**
+ * Stop timer tick
+ *
+ * @v booting		System is shutting down in order to boot
+ */
+static void efi_tick_shutdown ( int booting __unused ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Stop timer tick */
+	if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerCancel, 0 ) ) != 0 ){
+		rc = -EEFI ( efirc );
+		DBGC ( colour, "EFI could not stop timer tick: %s\n",
+		       strerror ( rc ) );
+		/* Self-destruct initiated */
+		return;
+	}
+	DBGC ( colour, "EFI timer stopped\n" );
+
+	/* Destroy timer tick event */
+	if ( ( efirc = bs->CloseEvent ( efi_tick_event ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		DBGC ( colour, "EFI could not destroy timer tick: %s\n",
+		       strerror ( rc ) );
+		/* Probably non-fatal */
+		return;
+	}
+}
+
+/** Timer tick startup function */
+struct startup_fn efi_tick_startup_fn __startup_fn ( STARTUP_EARLY ) = {
+	.name = "efi_tick",
+	.startup = efi_tick_startup,
+	.shutdown = efi_tick_shutdown,
+};
+
+/** EFI timer */
+struct timer efi_timer __timer ( TIMER_NORMAL ) = {
+	.name = "efi",
+	.currticks = efi_currticks,
+	.udelay = efi_udelay,
+};