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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <efi.h>
#include <efilib.h>
#if defined(__i386__) || defined(__x86_64__)
#include <cpuid.h>
#endif
#include "ticks.h"
#if defined(__i386__) || defined(__x86_64__)
static BOOLEAN in_hypervisor(void) {
uint32_t eax, ebx, ecx, edx;
/* The TSC might or might not be virtualized in VMs (and thus might not be accurate or start at zero
* at boot), depending on hypervisor and CPU functionality. If it's not virtualized it's not useful
* for keeping time, hence don't attempt to use it.
*
* This is a dumbed down version of src/basic/virt.c's detect_vm() that safely works in the UEFI
* environment. */
if (__get_cpuid(1, &eax, &ebx, &ecx, &edx) == 0)
return FALSE;
return !!(ecx & 0x80000000U);
}
#endif
#ifdef __x86_64__
static uint64_t ticks_read(void) {
uint64_t a, d;
if (in_hypervisor())
return 0;
__asm__ volatile ("rdtsc" : "=a" (a), "=d" (d));
return (d << 32) | a;
}
#elif defined(__i386__)
static uint64_t ticks_read(void) {
uint64_t val;
if (in_hypervisor())
return 0;
__asm__ volatile ("rdtsc" : "=A" (val));
return val;
}
#elif defined(__aarch64__)
static uint64_t ticks_read(void) {
uint64_t val;
__asm__ volatile ("mrs %0, cntpct_el0" : "=r" (val));
return val;
}
#else
static uint64_t ticks_read(void) {
return 0;
}
#endif
#if defined(__aarch64__)
static uint64_t ticks_freq(void) {
uint64_t freq;
__asm__ volatile ("mrs %0, cntfrq_el0": "=r" (freq));
return freq;
}
#else
/* count TSC ticks during a millisecond delay */
static uint64_t ticks_freq(void) {
uint64_t ticks_start, ticks_end;
static uint64_t cache = 0;
if (cache != 0)
return cache;
ticks_start = ticks_read();
BS->Stall(1000);
ticks_end = ticks_read();
if (ticks_end < ticks_start) /* Check for an overflow (which is not that unlikely, given on some
* archs the value is 32bit) */
return 0;
cache = (ticks_end - ticks_start) * 1000UL;
return cache;
}
#endif
uint64_t time_usec(void) {
uint64_t ticks, freq;
ticks = ticks_read();
if (ticks == 0)
return 0;
freq = ticks_freq();
if (freq == 0)
return 0;
return 1000UL * 1000UL * ticks / freq;
}
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