bpf: use libbpf_num_possible_cpus internally

Use the newly added bpf_num_possible_cpus() in bpftool and selftests
and remove duplicate implementations.
Signed-off-by: Hechao Li <hechaol@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/common.c

@@ -21,6 +21,7 @@
 #include <sys/vfs.h>
 
 #include <bpf.h>
+#include <libbpf.h> /* libbpf_num_possible_cpus */
 
 #include "main.h"
 
@@ -439,57 +440,13 @@ unsigned int get_page_size(void)
 
 unsigned int get_possible_cpus(void)
 {
-	static unsigned int result;
-	char buf[128];
-	long int n;
-	char *ptr;
-	int fd;
-
-	if (result)
-		return result;
-
-	fd = open("/sys/devices/system/cpu/possible", O_RDONLY);
-	if (fd < 0) {
-		p_err("can't open sysfs possible cpus");
-		exit(-1);
-	}
-
-	n = read(fd, buf, sizeof(buf));
-	if (n < 2) {
-		p_err("can't read sysfs possible cpus");
-		exit(-1);
-	}
-	close(fd);
+	int cpus = libbpf_num_possible_cpus();
 
-	if (n == sizeof(buf)) {
-		p_err("read sysfs possible cpus overflow");
+	if (cpus < 0) {
+		p_err("Can't get # of possible cpus: %s", strerror(-cpus));
 		exit(-1);
 	}
-
-	ptr = buf;
-	n = 0;
-	while (*ptr && *ptr != '\n') {
-		unsigned int a, b;
-
-		if (sscanf(ptr, "%u-%u", &a, &b) == 2) {
-			n += b - a + 1;
-
-			ptr = strchr(ptr, '-') + 1;
-		} else if (sscanf(ptr, "%u", &a) == 1) {
-			n++;
-		} else {
-			assert(0);
-		}
-
-		while (isdigit(*ptr))
-			ptr++;
-		if (*ptr == ',')
-			ptr++;
-	}
-
-	result = n;
-
-	return result;
+	return cpus;
 }
 
 static char *

tools/testing/selftests/bpf/bpf_util.h

@@ -6,44 +6,17 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#include <libbpf.h> /* libbpf_num_possible_cpus */
 
 static inline unsigned int bpf_num_possible_cpus(void)
 {
-	static const char *fcpu = "/sys/devices/system/cpu/possible";
-	unsigned int start, end, possible_cpus = 0;
-	char buff[128];
-	FILE *fp;
-	int len, n, i, j = 0;
+	int possible_cpus = libbpf_num_possible_cpus();
 
-	fp = fopen(fcpu, "r");
-	if (!fp) {
-		printf("Failed to open %s: '%s'!\n", fcpu, strerror(errno));
+	if (possible_cpus < 0) {
+		printf("Failed to get # of possible cpus: '%s'!\n",
+		       strerror(-possible_cpus));
 		exit(1);
 	}
-
-	if (!fgets(buff, sizeof(buff), fp)) {
-		printf("Failed to read %s!\n", fcpu);
-		exit(1);
-	}
-
-	len = strlen(buff);
-	for (i = 0; i <= len; i++) {
-		if (buff[i] == ',' || buff[i] == '\0') {
-			buff[i] = '\0';
-			n = sscanf(&buff[j], "%u-%u", &start, &end);
-			if (n <= 0) {
-				printf("Failed to retrieve # possible CPUs!\n");
-				exit(1);
-			} else if (n == 1) {
-				end = start;
-			}
-			possible_cpus += end - start + 1;
-			j = i + 1;
-		}
-	}
-
-	fclose(fp);
-
 	return possible_cpus;
 }