header.c

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#include <stdio.h>
#include <stdlib.h>
#include <api/fs/fs.h>
#include "header.h"

#define MIDR "/regs/identification/midr_el1"
#define MIDR_SIZE 19
#define MIDR_REVISION_MASK      0xf
#define MIDR_VARIANT_SHIFT      20
#define MIDR_VARIANT_MASK       (0xf << MIDR_VARIANT_SHIFT)

char *get_cpuid_str(struct perf_pmu *pmu)
{
    char *buf = NULL;
    char path[PATH_MAX];
    const char *sysfs = sysfs__mountpoint();
    int cpu;
    u64 midr = 0;
    struct cpu_map *cpus;
    FILE *file;

    if (!sysfs || !pmu || !pmu->cpus)
        return NULL;

    buf = malloc(MIDR_SIZE);
    if (!buf)
        return NULL;

    /* read midr from list of cpus mapped to this pmu */
    cpus = cpu_map__get(pmu->cpus);
    for (cpu = 0; cpu < cpus->nr; cpu++) {
        scnprintf(path, PATH_MAX, "%s/devices/system/cpu/cpu%d"MIDR,
                sysfs, cpus->map[cpu]);

        file = fopen(path, "r");
        if (!file) {
            pr_debug("fopen failed for file %s\n", path);
            continue;
        }

        if (!fgets(buf, MIDR_SIZE, file)) {
            fclose(file);
            continue;
        }
        fclose(file);

        /* Ignore/clear Variant[23:20] and
         * Revision[3:0] of MIDR
         */
        midr = strtoul(buf, NULL, 16);
        midr &= (~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK));
        scnprintf(buf, MIDR_SIZE, "0x%016lx", midr);
        /* got midr break loop */
        break;
    }

    if (!midr) {
        pr_err("failed to get cpuid string for PMU %s\n", pmu->name);
        free(buf);
        buf = NULL;
    }

    cpu_map__put(cpus);
    return buf;
}