linux-kernel - [PATCH 2/3] perf tools arm64: implement function get_cpuid

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Date:   Tue,  4 Apr 2017 13:06:42 +0530
From:   Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Will.Deacon@....com, catalin.marinas@....com, mark.rutland@....com,
        acme@...nel.org, alexander.shishkin@...ux.intel.com,
        peterz@...radead.org, mingo@...hat.com, jnair@...iumnetworks.com,
        gpkulkarni@...il.com
Subject: [PATCH 2/3] perf tools arm64: implement function get_cpuid_str

function get_cpuid_str returns midr_el1 value from first
online cpu available.

Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>
---
 tools/perf/arch/arm64/util/Build    |  1 +
 tools/perf/arch/arm64/util/header.c | 51 +++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)
 create mode 100644 tools/perf/arch/arm64/util/header.c

diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build
index cef6fb3..b1ab72d 100644
--- a/tools/perf/arch/arm64/util/Build
+++ b/tools/perf/arch/arm64/util/Build
@@ -1,3 +1,4 @@
+libperf-y += header.o
 libperf-$(CONFIG_DWARF)     += dwarf-regs.o
 libperf-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o
 
diff --git a/tools/perf/arch/arm64/util/header.c b/tools/perf/arch/arm64/util/header.c
new file mode 100644
index 0000000..c0468fe
--- /dev/null
+++ b/tools/perf/arch/arm64/util/header.c
@@ -0,0 +1,51 @@
+#include <fnmatch.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <linux/stringify.h>
+#include "header.h"
+#include "util.h"
+
+#define LINUX_SYS_CPU_DIRECTORY "/sys/devices/system/cpu/"
+#define MIDR "/regs/identification/midr_el1"
+
+char *get_cpuid_str(void)
+{
+	char *buf = malloc(128);
+	FILE *file;
+	char *ret = NULL;
+	int cpu , nr_cpu;
+	char sys_file[256];
+
+	sprintf(sys_file, LINUX_SYS_CPU_DIRECTORY"kernel_max");
+
+	file = fopen(sys_file, "r");
+	if (!file)
+		return ret;
+
+	if (fscanf(file, "%d", &nr_cpu) != 1)
+		return ret;
+
+	/* kernel_max returns nr_cpu -1 */
+	nr_cpu++;
+
+	/*iterate till you read midr of first online cpu */
+	for(cpu = 0; cpu < nr_cpu; cpu++)
+	{
+		sprintf(sys_file, LINUX_SYS_CPU_DIRECTORY"cpu%d"MIDR, cpu);
+		file = fopen(sys_file, "r");
+		if (file) {
+			ret = fgets(buf, 128, file);
+			if (ret) {
+				buf[strlen(buf)-1] ='\0';
+				fclose(file);
+				return buf;
+			}
+			fclose(file);
+		}
+	}
+	free(buf);
+	return ret;
+}
-- 
1.8.1.4