rdpmc.c
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#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/mman.h>
#include "types.h"
#include "perf.h"
#include "debug.h"
#include "tests.h"
#if defined(__x86_64__) || defined(__i386__)
static u64 rdpmc(unsigned int counter)
{
unsigned int low, high;
asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter));
return low | ((u64)high) << 32;
}
static u64 rdtsc(void)
{
unsigned int low, high;
asm volatile("rdtsc" : "=a" (low), "=d" (high));
return low | ((u64)high) << 32;
}
static u64 mmap_read_self(void *addr)
{
struct perf_event_mmap_page *pc = addr;
u32 seq, idx, time_mult = 0, time_shift = 0;
u64 count, cyc = 0, time_offset = 0, enabled, running, delta;
do {
seq = pc->lock;
barrier();
enabled = pc->time_enabled;
running = pc->time_running;
if (enabled != running) {
cyc = rdtsc();
time_mult = pc->time_mult;
time_shift = pc->time_shift;
time_offset = pc->time_offset;
}
idx = pc->index;
count = pc->offset;
if (idx)
count += rdpmc(idx - 1);
barrier();
} while (pc->lock != seq);
if (enabled != running) {
u64 quot, rem;
quot = (cyc >> time_shift);
rem = cyc & ((1 << time_shift) - 1);
delta = time_offset + quot * time_mult +
((rem * time_mult) >> time_shift);
enabled += delta;
if (idx)
running += delta;
quot = count / running;
rem = count % running;
count = quot * enabled + (rem * enabled) / running;
}
return count;
}
/*
* If the RDPMC instruction faults then signal this back to the test parent task:
*/
static void segfault_handler(int sig __maybe_unused,
siginfo_t *info __maybe_unused,
void *uc __maybe_unused)
{
exit(-1);
}
static int __test__rdpmc(void)
{
volatile int tmp = 0;
u64 i, loops = 1000;
int n;
int fd;
void *addr;
struct perf_event_attr attr = {
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_INSTRUCTIONS,
.exclude_kernel = 1,
};
u64 delta_sum = 0;
struct sigaction sa;
sigfillset(&sa.sa_mask);
sa.sa_sigaction = segfault_handler;
sigaction(SIGSEGV, &sa, NULL);
fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
if (fd < 0) {
pr_err("Error: sys_perf_event_open() syscall returned "
"with %d (%s)\n", fd, strerror(errno));
return -1;
}
addr = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0);
if (addr == (void *)(-1)) {
pr_err("Error: mmap() syscall returned with (%s)\n",
strerror(errno));
goto out_close;
}
for (n = 0; n < 6; n++) {
u64 stamp, now, delta;
stamp = mmap_read_self(addr);
for (i = 0; i < loops; i++)
tmp++;
now = mmap_read_self(addr);
loops *= 10;
delta = now - stamp;
pr_debug("%14d: %14Lu\n", n, (long long)delta);
delta_sum += delta;
}
munmap(addr, page_size);
pr_debug(" ");
out_close:
close(fd);
if (!delta_sum)
return -1;
return 0;
}
int test__rdpmc(void)
{
int status = 0;
int wret = 0;
int ret;
int pid;
pid = fork();
if (pid < 0)
return -1;
if (!pid) {
ret = __test__rdpmc();
exit(ret);
}
wret = waitpid(pid, &status, 0);
if (wret < 0 || status)
return -1;
return 0;
}
#endif