]> git.saurik.com Git - apple/xnu.git/blobdiff - osfmk/i386/acpi.c
xnu-7195.101.1.tar.gz
[apple/xnu.git] / osfmk / i386 / acpi.c
index 9bd836e2c29fb5587789a3b039f064ec3b772b53..2af7ed288cdeb4d23928625d0cd82271a0bbb36c 100644 (file)
@@ -1,8 +1,8 @@
 /*
- * Copyright (c) 2000-2012 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2018 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
- * 
+ *
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
  * unlawful or unlicensed copies of an Apple operating system, or to
  * circumvent, violate, or enable the circumvention or violation of, any
  * terms of an Apple operating system software license agreement.
- * 
+ *
  * Please obtain a copy of the License at
  * http://www.opensource.apple.com/apsl/ and read it before using this file.
- * 
+ *
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
@@ -22,7 +22,7 @@
  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  * Please see the License for the specific language governing rights and
  * limitations under the License.
- * 
+ *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 
 
 #include <i386/tsc.h>
 
+#define UINT64 uint64_t
+#define UINT32 uint32_t
+#define UINT16 uint16_t
+#define UINT8 uint8_t
+#define RSDP_VERSION_ACPI10     0
+#define RSDP_VERSION_ACPI20     2
+#include <acpi/Acpi.h>
+#include <acpi/Acpi_v1.h>
+#include <pexpert/i386/efi.h>
+
 #include <kern/cpu_data.h>
 #include <kern/machine.h>
 #include <kern/timer_queue.h>
 #include <IOKit/IOPlatformExpert.h>
 #include <sys/kdebug.h>
 
+#if MONOTONIC
+#include <kern/monotonic.h>
+#endif /* MONOTONIC */
+
 #if CONFIG_SLEEP
-extern void    acpi_sleep_cpu(acpi_sleep_callback, void * refcon);
-extern void    acpi_wake_prot(void);
+extern void     acpi_sleep_cpu(acpi_sleep_callback, void * refcon);
+extern void     acpi_wake_prot(void);
 #endif
 extern kern_return_t IOCPURunPlatformQuiesceActions(void);
 extern kern_return_t IOCPURunPlatformActiveActions(void);
 extern kern_return_t IOCPURunPlatformHaltRestartActions(uint32_t message);
 
-extern void    fpinit(void);
+extern void     fpinit(void);
+
+#if DEVELOPMENT || DEBUG
+#define DBG(x...) kprintf(x)
+#else
+#define DBG(x...)
+#endif
 
 vm_offset_t
 acpi_install_wake_handler(void)
@@ -91,11 +111,11 @@ acpi_install_wake_handler(void)
 
 #if CONFIG_SLEEP
 
-unsigned int           save_kdebug_enable = 0;
-static uint64_t                acpi_sleep_abstime;
-static uint64_t                acpi_idle_abstime;
-static uint64_t                acpi_wake_abstime, acpi_wake_postrebase_abstime;
-boolean_t              deep_idle_rebase = TRUE;
+unsigned int            save_kdebug_enable = 0;
+static uint64_t         acpi_sleep_abstime;
+static uint64_t         acpi_idle_abstime;
+static uint64_t         acpi_wake_abstime, acpi_wake_postrebase_abstime;
+boolean_t               deep_idle_rebase = TRUE;
 
 #if HIBERNATION
 struct acpi_hibernate_callback_data {
@@ -110,36 +130,37 @@ acpi_hibernate(void *refcon)
        uint32_t mode;
 
        acpi_hibernate_callback_data_t *data =
-               (acpi_hibernate_callback_data_t *)refcon;
+           (acpi_hibernate_callback_data_t *)refcon;
 
-       if (current_cpu_datap()->cpu_hibernate) 
-       {
+       if (current_cpu_datap()->cpu_hibernate) {
                mode = hibernate_write_image();
 
-               if( mode == kIOHibernatePostWriteHalt )
-               {
+               if (mode == kIOHibernatePostWriteHalt) {
                        // off
                        HIBLOG("power off\n");
                        IOCPURunPlatformHaltRestartActions(kPEHaltCPU);
-                       if (PE_halt_restart) (*PE_halt_restart)(kPEHaltCPU);
-               }
-               else if( mode == kIOHibernatePostWriteRestart )
-               {
+                       if (PE_halt_restart) {
+                               (*PE_halt_restart)(kPEHaltCPU);
+                       }
+               } else if (mode == kIOHibernatePostWriteRestart) {
                        // restart
                        HIBLOG("restart\n");
                        IOCPURunPlatformHaltRestartActions(kPERestartCPU);
-                       if (PE_halt_restart) (*PE_halt_restart)(kPERestartCPU);
-               }
-               else
-               {
+                       if (PE_halt_restart) {
+                               (*PE_halt_restart)(kPERestartCPU);
+                       }
+               } else {
                        // sleep
                        HIBLOG("sleep\n");
-       
+
                        // should we come back via regular wake, set the state in memory.
-                       cpu_datap(0)->cpu_hibernate = 0;                        
+                       cpu_datap(0)->cpu_hibernate = 0;
                }
-
        }
+
+#if CONFIG_VMX
+       vmx_suspend();
+#endif
        kdebug_enable = 0;
 
        IOCPURunPlatformQuiesceActions();
@@ -153,10 +174,7 @@ acpi_hibernate(void *refcon)
 #endif /* HIBERNATION */
 #endif /* CONFIG_SLEEP */
 
-extern void                    slave_pstart(void);
-extern void                    hibernate_rebuild_vm_structs(void);
-
-extern unsigned int            wake_nkdbufs;
+extern void                     slave_pstart(void);
 
 void
 acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
@@ -165,35 +183,42 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
        acpi_hibernate_callback_data_t data;
 #endif
        boolean_t did_hibernate;
-       unsigned int    cpu;
-       kern_return_t   rc;
-       unsigned int    my_cpu;
-       uint64_t        start;
-       uint64_t        elapsed = 0;
-       uint64_t        elapsed_trace_start = 0;
-
-       kprintf("acpi_sleep_kernel hib=%d, cpu=%d\n",
-                       current_cpu_datap()->cpu_hibernate, cpu_number());
-
-       /* Get all CPUs to be in the "off" state */
-       my_cpu = cpu_number();
+       cpu_data_t *cdp = current_cpu_datap();
+       unsigned int    cpu;
+       kern_return_t   rc;
+       unsigned int    my_cpu;
+       uint64_t        start;
+       uint64_t        elapsed = 0;
+       uint64_t        elapsed_trace_start = 0;
+
+       my_cpu = cpu_number();
+       kprintf("acpi_sleep_kernel hib=%d, cpu=%d\n", cdp->cpu_hibernate,
+           my_cpu);
+
+       /* Get all CPUs to be in the "off" state */
        for (cpu = 0; cpu < real_ncpus; cpu += 1) {
-               if (cpu == my_cpu)
+               if (cpu == my_cpu) {
                        continue;
+               }
                rc = pmCPUExitHaltToOff(cpu);
-               if (rc != KERN_SUCCESS)
+               if (rc != KERN_SUCCESS) {
                        panic("Error %d trying to transition CPU %d to OFF",
-                             rc, cpu);
+                           rc, cpu);
+               }
        }
 
        /* shutdown local APIC before passing control to firmware */
-       lapic_shutdown();
+       lapic_shutdown(true);
 
 #if HIBERNATION
        data.func = func;
        data.refcon = refcon;
 #endif
 
+#if MONOTONIC
+       mt_cpu_down(cdp);
+#endif /* MONOTONIC */
+
        /* Save power management timer state */
        pmTimerSave();
 
@@ -202,19 +227,12 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
        hv_suspend();
 #endif
 
-#if CONFIG_VMX
-       /* 
-        * Turn off VT, otherwise switching to legacy mode will fail
-        */
-       vmx_suspend();
-#endif
-
        /*
         * Enable FPU/SIMD unit for potential hibernate acceleration
         */
-       clear_ts(); 
+       clear_ts();
 
-       KERNEL_DEBUG_CONSTANT(IOKDBG_CODE(DBG_HIBERNATE, 0) | DBG_FUNC_START, 0, 0, 0, 0, 0);
+       KDBG(IOKDBG_CODE(DBG_HIBERNATE, 0) | DBG_FUNC_START);
 
        save_kdebug_enable = kdebug_enable;
        kdebug_enable = 0;
@@ -231,10 +249,19 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
 #if HIBERNATION
        acpi_sleep_cpu(acpi_hibernate, &data);
 #else
+#if CONFIG_VMX
+       vmx_suspend();
+#endif
        acpi_sleep_cpu(func, refcon);
 #endif
 
-       start = mach_absolute_time();
+       acpi_wake_abstime = mach_absolute_time();
+       /* Rebase TSC->absolute time conversion, using timestamp
+        * recorded before sleep.
+        */
+       rtc_nanotime_init(acpi_sleep_abstime);
+       acpi_wake_postrebase_abstime = start = mach_absolute_time();
+       assert(start >= acpi_sleep_abstime);
 
        x86_64_post_sleep(old_cr3);
 
@@ -245,21 +272,21 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
         * for compatibility with firewire kprintf.
         */
 
-       if (FALSE == disable_serial_output)
+       if (FALSE == disable_serial_output) {
                pal_serial_init();
+       }
 
 #if HIBERNATION
        if (current_cpu_datap()->cpu_hibernate) {
                did_hibernate = TRUE;
-
        } else
-#endif 
+#endif
        {
                did_hibernate = FALSE;
        }
 
-       /* Re-enable mode (including 64-bit if applicable) */
-       cpu_mode_init(current_cpu_datap());
+       /* Re-enable fast syscall */
+       cpu_syscall_init(current_cpu_datap());
 
 #if CONFIG_MCA
        /* Re-enable machine check handling */
@@ -271,21 +298,21 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
        mtrr_update_cpu();
 #endif
 
-       /* update CPU microcode */
-       ucode_update_wake();
-
-#if CONFIG_VMX
-       /* 
-        * Restore VT mode
-        */
-       vmx_resume();
-#endif
+       /* update CPU microcode and apply CPU workarounds */
+       ucode_update_wake_and_apply_cpu_was();
 
 #if CONFIG_MTRR
        /* set up PAT following boot processor power up */
        pat_init();
 #endif
 
+#if CONFIG_VMX
+       /*
+        * Restore VT mode
+        */
+       vmx_resume(did_hibernate);
+#endif
+
        /*
         * Go through all of the CPUs and mark them as requiring
         * a full restart.
@@ -294,29 +321,25 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
 
 
        /* re-enable and re-init local apic (prior to starting timers) */
-       if (lapic_probe())
-               lapic_configure();
+       if (lapic_probe()) {
+               lapic_configure(true);
+       }
 
-#if HIBERNATION
-       hibernate_rebuild_vm_structs();
+#if KASAN
+       /*
+        * The sleep implementation uses indirect noreturn calls, so we miss stack
+        * unpoisoning. Do it explicitly.
+        */
+       kasan_unpoison_curstack(true);
 #endif
 
        elapsed += mach_absolute_time() - start;
-       acpi_wake_abstime = mach_absolute_time();
-
-       /* let the realtime clock reset */
-       rtc_sleep_wakeup(acpi_sleep_abstime);
-       acpi_wake_postrebase_abstime = mach_absolute_time();
-       assert(mach_absolute_time() >= acpi_sleep_abstime);
 
+       rtc_decrementer_configure();
        kdebug_enable = save_kdebug_enable;
 
        if (kdebug_enable == 0) {
-               if (wake_nkdbufs) {
-                       start = mach_absolute_time();
-                       start_kern_tracing(wake_nkdbufs, TRUE);
-                       elapsed_trace_start += mach_absolute_time() - start;
-               }
+               elapsed_trace_start += kdebug_wake();
        }
        start = mach_absolute_time();
 
@@ -324,22 +347,16 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
        init_fpu();
        clear_ts();
 
-       IOCPURunPlatformActiveActions();
 
-#if HIBERNATION
-       if (did_hibernate) {
-               elapsed += mach_absolute_time() - start;
-               
-               KERNEL_DEBUG_CONSTANT(IOKDBG_CODE(DBG_HIBERNATE, 2) | DBG_FUNC_START, elapsed, elapsed_trace_start, 0, 0, 0);
-               hibernate_machine_init();
-               KERNEL_DEBUG_CONSTANT(IOKDBG_CODE(DBG_HIBERNATE, 2) | DBG_FUNC_END, 0, 0, 0, 0, 0);
+#if HYPERVISOR
+       /* Notify hypervisor that we are about to resume */
+       hv_resume();
+#endif
 
-               current_cpu_datap()->cpu_hibernate = 0;
+       IOCPURunPlatformActiveActions();
 
-               KERNEL_DEBUG_CONSTANT(IOKDBG_CODE(DBG_HIBERNATE, 0) | DBG_FUNC_END, 0, 0, 0, 0, 0);
-       } else
-#endif /* HIBERNATION */
-               KERNEL_DEBUG_CONSTANT(IOKDBG_CODE(DBG_HIBERNATE, 0) | DBG_FUNC_END, 0, 0, 0, 0, 0);
+       KDBG(IOKDBG_CODE(DBG_HIBERNATE, 0) | DBG_FUNC_END, start, elapsed,
+           elapsed_trace_start, acpi_wake_abstime);
 
        /* Restore power management register state */
        pmCPUMarkRunning(current_cpu_datap());
@@ -350,17 +367,41 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
        /* Restart timer interrupts */
        rtc_timer_start();
 
-#if HIBERNATION
+#if MONOTONIC
+       mt_cpu_up(cdp);
+#endif /* MONOTONIC */
 
+#if HIBERNATION
        kprintf("ret from acpi_sleep_cpu hib=%d\n", did_hibernate);
-#endif
+#endif /* HIBERNATION */
 
 #if CONFIG_SLEEP
        /* Becase we don't save the bootstrap page, and we share it
-        * between sleep and mp slave init, we need to recreate it 
+        * between sleep and mp slave init, we need to recreate it
         * after coming back from sleep or hibernate */
        install_real_mode_bootstrap(slave_pstart);
-#endif
+#endif /* CONFIG_SLEEP */
+}
+
+void
+ml_hibernate_active_pre(void)
+{
+#if HIBERNATION
+       hibernate_rebuild_vm_structs();
+#endif /* HIBERNATION */
+}
+
+void
+ml_hibernate_active_post(void)
+{
+#if HIBERNATION
+       if (current_cpu_datap()->cpu_hibernate) {
+               KDBG(IOKDBG_CODE(DBG_HIBERNATE, 2) | DBG_FUNC_START);
+               hibernate_machine_init();
+               KDBG(IOKDBG_CODE(DBG_HIBERNATE, 2) | DBG_FUNC_END);
+               current_cpu_datap()->cpu_hibernate = 0;
+       }
+#endif /* HIBERNATION */
 }
 
 /*
@@ -378,31 +419,41 @@ acpi_sleep_kernel(acpi_sleep_callback func, void *refcon)
 void
 acpi_idle_kernel(acpi_sleep_callback func, void *refcon)
 {
-       boolean_t       istate = ml_get_interrupts_enabled();
-       
+       boolean_t       istate = ml_get_interrupts_enabled();
+
        kprintf("acpi_idle_kernel, cpu=%d, interrupts %s\n",
-               cpu_number(), istate ? "enabled" : "disabled");
+           cpu_number(), istate ? "enabled" : "disabled");
 
        assert(cpu_number() == master_cpu);
 
-       /*
-        * Effectively set the boot cpu offline.
-        * This will stop further deadlines being set.
-        */
-       cpu_datap(master_cpu)->cpu_running = FALSE;
+#if MONOTONIC
+       mt_cpu_down(cpu_datap(0));
+#endif /* MONOTONIC */
 
        /* Cancel any pending deadline */
        setPop(0);
-       while (lapic_is_interrupting(LAPIC_TIMER_VECTOR)) {
+       while (lapic_is_interrupting(LAPIC_TIMER_VECTOR)
+#if MONOTONIC
+           || lapic_is_interrupting(LAPIC_VECTOR(PERFCNT))
+#endif /* MONOTONIC */
+           ) {
                (void) ml_set_interrupts_enabled(TRUE);
                setPop(0);
                ml_set_interrupts_enabled(FALSE);
        }
 
+       if (current_cpu_datap()->cpu_hibernate) {
+               /* Call hibernate_write_image() to put disk to low power state */
+               hibernate_write_image();
+               cpu_datap(0)->cpu_hibernate = 0;
+       }
+
        /*
         * Call back to caller to indicate that interrupts will remain
         * disabled while we deep idle, wake and return.
-        */ 
+        */
+       IOCPURunPlatformQuiesceActions();
+
        func(refcon);
 
        acpi_idle_abstime = mach_absolute_time();
@@ -431,7 +482,7 @@ acpi_idle_kernel(acpi_sleep_callback func, void *refcon)
         * Get wakeup time relative to the TSC which has progressed.
         * Then rebase nanotime to reflect time not progressing over sleep
         * - unless overriden so that tracing can occur during deep_idle.
-        */ 
+        */
        acpi_wake_abstime = mach_absolute_time();
        if (deep_idle_rebase) {
                rtc_sleep_wakeup(acpi_idle_abstime);
@@ -439,16 +490,18 @@ acpi_idle_kernel(acpi_sleep_callback func, void *refcon)
        }
        acpi_wake_postrebase_abstime = mach_absolute_time();
        assert(mach_absolute_time() >= acpi_idle_abstime);
-       cpu_datap(master_cpu)->cpu_running = TRUE;
 
        KERNEL_DEBUG_CONSTANT(
                MACHDBG_CODE(DBG_MACH_SCHED, MACH_DEEP_IDLE) | DBG_FUNC_END,
                acpi_wake_abstime, acpi_wake_abstime - acpi_idle_abstime, 0, 0, 0);
-       /* Like S3 sleep, turn on tracing if trace_wake boot-arg is present */ 
+
+#if MONOTONIC
+       mt_cpu_up(cpu_datap(0));
+#endif /* MONOTONIC */
+
+       /* Like S3 sleep, turn on tracing if trace_wake boot-arg is present */
        if (kdebug_enable == 0) {
-               if (wake_nkdbufs)
-                       start_kern_tracing(wake_nkdbufs, TRUE);
+               kdebug_wake();
        }
 
        IOCPURunPlatformActiveActions();
@@ -471,24 +524,223 @@ install_real_mode_bootstrap(void *prot_entry)
         * mode and then jumping to the common startup, _start().
         */
        bcopy_phys(kvtophys((vm_offset_t) real_mode_bootstrap_base),
-                  (addr64_t) REAL_MODE_BOOTSTRAP_OFFSET,
-                  real_mode_bootstrap_end-real_mode_bootstrap_base);
+           (addr64_t) REAL_MODE_BOOTSTRAP_OFFSET,
+           real_mode_bootstrap_end - real_mode_bootstrap_base);
 
        /*
         * Set the location at the base of the stack to point to the
         * common startup entry.
         */
        ml_phys_write_word(
-               PROT_MODE_START+REAL_MODE_BOOTSTRAP_OFFSET,
+               PROT_MODE_START + REAL_MODE_BOOTSTRAP_OFFSET,
                (unsigned int)kvtophys((vm_offset_t)prot_entry));
-       
+
        /* Flush caches */
        __asm__("wbinvd");
 }
 
 boolean_t
-ml_recent_wake(void) {
+ml_recent_wake(void)
+{
        uint64_t ctime = mach_absolute_time();
        assert(ctime > acpi_wake_postrebase_abstime);
-       return ((ctime - acpi_wake_postrebase_abstime) < 5 * NSEC_PER_SEC);
+       return (ctime - acpi_wake_postrebase_abstime) < 5 * NSEC_PER_SEC;
+}
+
+static uint8_t
+cksum8(uint8_t *ptr, uint32_t size)
+{
+       uint8_t sum = 0;
+       uint32_t i;
+
+       for (i = 0; i < size; i++) {
+               sum += ptr[i];
+       }
+
+       return sum;
+}
+
+/*
+ * Parameterized search for a specified table given an sdtp (either RSDT or XSDT).
+ * Note that efiboot does not modify the addresses of tables in the RSDT or XSDT
+ * TableOffsetEntry array, so we do not need to "convert" from efiboot virtual to
+ * physical.
+ */
+#define SEARCH_FOR_ACPI_TABLE(sdtp, signature, entry_type) \
+{                                                                                               \
+       uint32_t i, pointer_count;                                                              \
+                                                                                                \
+       /* Walk the list of tables in the *SDT, looking for the signature passed in */          \
+       pointer_count = ((sdtp)->Length - sizeof(ACPI_TABLE_HEADER)) / sizeof(entry_type);      \
+                                                                                                \
+       for (i = 0; i < pointer_count; i++) {                                                   \
+               ACPI_TABLE_HEADER *next_table =                                                 \
+                       (ACPI_TABLE_HEADER *)PHYSMAP_PTOV(                                      \
+                               (uintptr_t)(sdtp)->TableOffsetEntry[i]);                        \
+               if (strncmp(&next_table->Signature[0], (signature), 4) == 0) {                  \
+       /* \
+        * Checksum the table first, then return it if the checksum \
+        * is valid. \
+        */                                                                                     \
+                       if (cksum8((uint8_t *)next_table, next_table->Length) == 0) {           \
+                               return next_table;                                              \
+                       } else {                                                                \
+                               DBG("Invalid checksum for table [%s]@0x%lx!\n", (signature),    \
+                                   (unsigned long)(sdtp)->TableOffsetEntry[i]);                \
+                               return NULL;                                                    \
+                       }                                                                       \
+               }                                                                               \
+       }                                                                                       \
+                                                                                                \
+       return NULL;                                                                            \
+}
+
+static ACPI_TABLE_HEADER *
+acpi_find_table_via_xsdt(XSDT_DESCRIPTOR *xsdtp, const char *signature)
+{
+       SEARCH_FOR_ACPI_TABLE(xsdtp, signature, UINT64);
+}
+
+static ACPI_TABLE_HEADER *
+acpi_find_table_via_rsdt(RSDT_DESCRIPTOR *rsdtp, const char *signature)
+{
+       SEARCH_FOR_ACPI_TABLE(rsdtp, signature, UINT32);
+}
+
+/*
+ * Returns a pointer to an ACPI table header corresponding to the table
+ * whose signature is passed in, or NULL if no such table could be found.
+ */
+static ACPI_TABLE_HEADER *
+acpi_find_table(uintptr_t rsdp_physaddr, const char *signature)
+{
+       static RSDP_DESCRIPTOR *rsdp = NULL;
+       static XSDT_DESCRIPTOR *xsdtp = NULL;
+       static RSDT_DESCRIPTOR *rsdtp = NULL;
+
+       if (signature == NULL) {
+               DBG("Invalid NULL signature passed to acpi_find_table\n");
+               return NULL;
+       }
+
+       /*
+        * RSDT or XSDT is required; without it, we cannot locate other tables.
+        */
+       if (__improbable(rsdp == NULL || (rsdtp == NULL && xsdtp == NULL))) {
+               rsdp = PHYSMAP_PTOV(rsdp_physaddr);
+
+               /* Verify RSDP signature */
+               if (__improbable(strncmp((void *)rsdp, "RSD PTR ", 8) != 0)) {
+                       DBG("RSDP signature mismatch: Aborting acpi_find_table\n");
+                       rsdp = NULL;
+                       return NULL;
+               }
+
+               /* Verify RSDP checksum */
+               if (__improbable(cksum8((uint8_t *)rsdp, sizeof(RSDP_DESCRIPTOR)) != 0)) {
+                       DBG("RSDP@0x%lx signature mismatch: Aborting acpi_find_table\n",
+                           (unsigned long)rsdp_physaddr);
+                       rsdp = NULL;
+                       return NULL;
+               }
+
+               /* Ensure the revision of the RSDP indicates the presence of an RSDT or XSDT */
+               if (__improbable(rsdp->Revision >= RSDP_VERSION_ACPI20 && rsdp->XsdtPhysicalAddress == 0ULL)) {
+                       DBG("RSDP XSDT Physical Address is 0!: Aborting acpi_find_table\n");
+                       rsdp = NULL;
+                       return NULL;
+               } else if (__probable(rsdp->Revision >= RSDP_VERSION_ACPI20)) {
+                       /* XSDT (with 64-bit pointers to tables) */
+                       rsdtp = NULL;
+                       xsdtp = PHYSMAP_PTOV(rsdp->XsdtPhysicalAddress);
+                       if (cksum8((uint8_t *)xsdtp, xsdtp->Length) != 0) {
+                               DBG("ERROR: XSDT@0x%lx checksum is non-zero; not using this XSDT\n",
+                                   (unsigned long)rsdp->XsdtPhysicalAddress);
+                               xsdtp = NULL;
+                               return NULL;
+                       }
+               } else if (__improbable(rsdp->Revision == RSDP_VERSION_ACPI10 && rsdp->RsdtPhysicalAddress == 0)) {
+                       DBG("RSDP RSDT Physical Address is 0!: Aborting acpi_find_table\n");
+                       rsdp = NULL;
+                       return NULL;
+               } else if (__improbable(rsdp->Revision == RSDP_VERSION_ACPI10)) {
+                       /* RSDT (with 32-bit pointers to tables) */
+                       xsdtp = NULL;
+                       rsdtp = PHYSMAP_PTOV((uintptr_t)rsdp->RsdtPhysicalAddress);
+                       if (cksum8((uint8_t *)rsdtp, rsdtp->Length) != 0) {
+                               DBG("ERROR: RSDT@0x%lx checksum is non-zero; not using this RSDT\n",
+                                   (unsigned long)rsdp->RsdtPhysicalAddress);
+                               rsdtp = NULL;
+                               return NULL;
+                       }
+               } else {
+                       DBG("Unrecognized RSDP Revision (0x%x): Aborting acpi_find_table\n",
+                           rsdp->Revision);
+                       rsdp = NULL;
+                       return NULL;
+               }
+       }
+
+       assert(xsdtp != NULL || rsdtp != NULL);
+
+       if (__probable(xsdtp != NULL)) {
+               return acpi_find_table_via_xsdt(xsdtp, signature);
+       } else if (rsdtp != NULL) {
+               return acpi_find_table_via_rsdt(rsdtp, signature);
+       }
+
+       return NULL;
+}
+
+/*
+ * Returns the count of enabled logical processors present in the ACPI
+ * MADT, or 0 if the MADT could not be located.
+ */
+uint32_t
+acpi_count_enabled_logical_processors(void)
+{
+       MULTIPLE_APIC_TABLE *madtp;
+       void *end_ptr;
+       APIC_HEADER *next_apic_entryp;
+       uint32_t enabled_cpu_count = 0;
+       uint64_t rsdp_physaddr;
+
+       rsdp_physaddr = efi_get_rsdp_physaddr();
+       if (__improbable(rsdp_physaddr == 0)) {
+               DBG("acpi_count_enabled_logical_processors: Could not get RSDP physaddr from EFI.\n");
+               return 0;
+       }
+
+       madtp = (MULTIPLE_APIC_TABLE *)acpi_find_table(rsdp_physaddr, ACPI_SIG_MADT);
+
+       if (__improbable(madtp == NULL)) {
+               DBG("acpi_count_enabled_logical_processors: Could not find the MADT.\n");
+               return 0;
+       }
+
+       end_ptr = (void *)((uintptr_t)madtp + madtp->Length);
+       next_apic_entryp = (APIC_HEADER *)((uintptr_t)madtp + sizeof(MULTIPLE_APIC_TABLE));
+
+       while ((void *)next_apic_entryp < end_ptr) {
+               switch (next_apic_entryp->Type) {
+               case APIC_PROCESSOR:
+               {
+                       MADT_PROCESSOR_APIC *madt_procp = (MADT_PROCESSOR_APIC *)next_apic_entryp;
+                       if (madt_procp->ProcessorEnabled) {
+                               enabled_cpu_count++;
+                       }
+
+                       break;
+               }
+
+               default:
+                       DBG("Ignoring MADT entry type 0x%x length 0x%x\n", next_apic_entryp->Type,
+                           next_apic_entryp->Length);
+                       break;
+               }
+
+               next_apic_entryp = (APIC_HEADER *)((uintptr_t)next_apic_entryp + next_apic_entryp->Length);
+       }
+
+       return enabled_cpu_count;
 }