Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/perf/lib/lib.c b/tools/perf/lib/lib.c
new file mode 100644
index 0000000..1865893
--- /dev/null
+++ b/tools/perf/lib/lib.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <unistd.h>
+#include <stdbool.h>
+#include <errno.h>
+#include <linux/kernel.h>
+#include <internal/lib.h>
+
+unsigned int page_size;
+
+static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
+{
+ void *buf_start = buf;
+ size_t left = n;
+
+ while (left) {
+ /* buf must be treated as const if !is_read. */
+ ssize_t ret = is_read ? read(fd, buf, left) :
+ write(fd, buf, left);
+
+ if (ret < 0 && errno == EINTR)
+ continue;
+ if (ret <= 0)
+ return ret;
+
+ left -= ret;
+ buf += ret;
+ }
+
+ BUG_ON((size_t)(buf - buf_start) != n);
+ return n;
+}
+
+/*
+ * Read exactly 'n' bytes or return an error.
+ */
+ssize_t readn(int fd, void *buf, size_t n)
+{
+ return ion(true, fd, buf, n);
+}
+
+/*
+ * Write exactly 'n' bytes or return an error.
+ */
+ssize_t writen(int fd, const void *buf, size_t n)
+{
+ /* ion does not modify buf. */
+ return ion(false, fd, (void *)buf, n);
+}