perf tools riscv: Add support for get_cpuid_str function

The get_cpuid_str function returns the string that contains values of
MVENDORID, MARCHID and MIMPID in hex format separated by coma.

The values themselves are taken from first cpu entry in "/proc/cpuid"
that contains "mvendorid", "marchid" and "mimpid".
Signed-off-by: Nikita Shubin <n.shubin@yadro.com>
Tested-by: Kautuk Consul <kconsul@ventanamicro.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Anup Patel <anup@brainfault.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-riscv@lists.infradead.org
Cc: linux@yadro.com
Link: https://lore.kernel.org/r/20220815132251.25702-2-nikita.shubin@maquefel.meSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/riscv/util/Build

 perf-y += perf_regs.o
+perf-y += header.o
 
 perf-$(CONFIG_DWARF) += dwarf-regs.o
 perf-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o

tools/perf/arch/riscv/util/header.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Implementation of get_cpuid().
+ *
+ * Author: Nikita Shubin <n.shubin@yadro.com>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <api/fs/fs.h>
+#include <errno.h>
+#include "../../util/debug.h"
+#include "../../util/header.h"
+
+#define CPUINFO_MVEN	"mvendorid"
+#define CPUINFO_MARCH	"marchid"
+#define CPUINFO_MIMP	"mimpid"
+#define CPUINFO		"/proc/cpuinfo"
+
+static char *_get_field(const char *line)
+{
+	char *line2, *nl;
+
+	line2 = strrchr(line, ' ');
+	if (!line2)
+		return NULL;
+
+	line2++;
+	nl = strrchr(line, '\n');
+	if (!nl)
+		return NULL;
+
+	return strndup(line2, nl - line2);
+}
+
+static char *_get_cpuid(void)
+{
+	char *line = NULL;
+	char *mvendorid = NULL;
+	char *marchid = NULL;
+	char *mimpid = NULL;
+	char *cpuid = NULL;
+	int read;
+	unsigned long line_sz;
+	FILE *cpuinfo;
+
+	cpuinfo = fopen(CPUINFO, "r");
+	if (cpuinfo == NULL)
+		return cpuid;
+
+	while ((read = getline(&line, &line_sz, cpuinfo)) != -1) {
+		if (!strncmp(line, CPUINFO_MVEN, strlen(CPUINFO_MVEN))) {
+			mvendorid = _get_field(line);
+			if (!mvendorid)
+				goto free;
+		} else if (!strncmp(line, CPUINFO_MARCH, strlen(CPUINFO_MARCH))) {
+			marchid = _get_field(line);
+			if (!marchid)
+				goto free;
+		} else if (!strncmp(line, CPUINFO_MIMP, strlen(CPUINFO_MIMP))) {
+			mimpid = _get_field(line);
+			if (!mimpid)
+				goto free;
+
+			break;
+		}
+	}
+
+	if (!mvendorid || !marchid || !mimpid)
+		goto free;
+
+	if (asprintf(&cpuid, "%s-%s-%s", mvendorid, marchid, mimpid) < 0)
+		cpuid = NULL;
+
+free:
+	fclose(cpuinfo);
+	free(mvendorid);
+	free(marchid);
+	free(mimpid);
+
+	return cpuid;
+}
+
+int get_cpuid(char *buffer, size_t sz)
+{
+	char *cpuid = _get_cpuid();
+	int ret = 0;
+
+	if (sz < strlen(cpuid)) {
+		ret = -EINVAL;
+		goto free;
+	}
+
+	scnprintf(buffer, sz, "%s", cpuid);
+free:
+	free(cpuid);
+	return ret;
+}
+
+char *
+get_cpuid_str(struct perf_pmu *pmu __maybe_unused)
+{
+	return _get_cpuid();
+}