branch-counter.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <linux/perf_event.h>
#include <asm/unistd.h>
#include <sys/ioctl.h>

static inline
int sys_perf_event_open(struct perf_event_attr *attr,
                pid_t pid, int cpu, int group_fd,
                unsigned long flags)
{
        attr->size = sizeof(*attr);
        return syscall(__NR_perf_event_open, attr, pid, cpu,
                        group_fd, flags);
}

static inline
void write_pmcnt_register()
{
        asm volatile ("mcr p15, 0, r0, c9, c13, 2" :: );
}

int main()
{
        struct perf_event_attr attr;

        memset(&attr, '\0', sizeof(attr));

        attr.disabled = 1;
        attr.type = PERF_TYPE_HARDWARE;
        attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;

        int fd = sys_perf_event_open(&attr, 0, -1, -1, 0);

        ioctl(fd, PERF_EVENT_IOC_ENABLE);

        write_pmcnt_register();
}