1 files changed, 193 insertions, 0 deletions
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
new file mode 100644
index 000000000000..9f2839e73f8a
--- /dev/null
+++ b/include/linux/seq_buf.h
@@ -0,0 +1,193 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_SEQ_BUF_H
+#define _LINUX_SEQ_BUF_H
+
+#include <linux/bug.h>
+#include <linux/minmax.h>
+#include <linux/seq_file.h>
+#include <linux/types.h>
+
+/*
+ * Trace sequences are used to allow a function to call several other functions
+ * to create a string of data to use.
+ */
+
+/**
+ * struct seq_buf - seq buffer structure
+ * @buffer:	pointer to the buffer
+ * @size:	size of the buffer
+ * @len:	the amount of data inside the buffer
+ */
+struct seq_buf {
+	char			*buffer;
+	size_t			size;
+	size_t			len;
+};
+
+#define DECLARE_SEQ_BUF(NAME, SIZE)			\
+	struct seq_buf NAME = {				\
+		.buffer = (char[SIZE]) { 0 },		\
+		.size = SIZE,				\
+	}
+
+static inline void seq_buf_clear(struct seq_buf *s)
+{
+	s->len = 0;
+	if (s->size)
+		s->buffer[0] = '\0';
+}
+
+static inline void
+seq_buf_init(struct seq_buf *s, char *buf, unsigned int size)
+{
+	s->buffer = buf;
+	s->size = size;
+	seq_buf_clear(s);
+}
+
+/*
+ * seq_buf have a buffer that might overflow. When this happens
+ * len is set to be greater than size.
+ */
+static inline bool
+seq_buf_has_overflowed(struct seq_buf *s)
+{
+	return s->len > s->size;
+}
+
+static inline void
+seq_buf_set_overflow(struct seq_buf *s)
+{
+	s->len = s->size + 1;
+}
+
+/*
+ * How much buffer is left on the seq_buf?
+ */
+static inline unsigned int
+seq_buf_buffer_left(struct seq_buf *s)
+{
+	if (seq_buf_has_overflowed(s))
+		return 0;
+
+	return s->size - s->len;
+}
+
+/* How much buffer was written? */
+static inline unsigned int seq_buf_used(struct seq_buf *s)
+{
+	return min(s->len, s->size);
+}
+
+/**
+ * seq_buf_str - get NUL-terminated C string from seq_buf
+ * @s: the seq_buf handle
+ *
+ * This makes sure that the buffer in @s is NUL-terminated and
+ * safe to read as a string.
+ *
+ * Note, if this is called when the buffer has overflowed, then
+ * the last byte of the buffer is zeroed, and the len will still
+ * point passed it.
+ *
+ * After this function is called, s->buffer is safe to use
+ * in string operations.
+ *
+ * Returns: @s->buf after making sure it is terminated.
+ */
+static inline const char *seq_buf_str(struct seq_buf *s)
+{
+	if (WARN_ON(s->size == 0))
+		return "";
+
+	if (seq_buf_buffer_left(s))
+		s->buffer[s->len] = 0;
+	else
+		s->buffer[s->size - 1] = 0;
+
+	return s->buffer;
+}
+
+/**
+ * seq_buf_get_buf - get buffer to write arbitrary data to
+ * @s: the seq_buf handle
+ * @bufp: the beginning of the buffer is stored here
+ *
+ * Returns: the number of bytes available in the buffer, or zero if
+ * there's no space.
+ */
+static inline size_t seq_buf_get_buf(struct seq_buf *s, char **bufp)
+{
+	WARN_ON(s->len > s->size + 1);
+
+	if (s->len < s->size) {
+		*bufp = s->buffer + s->len;
+		return s->size - s->len;
+	}
+
+	*bufp = NULL;
+	return 0;
+}
+
+/**
+ * seq_buf_commit - commit data to the buffer
+ * @s: the seq_buf handle
+ * @num: the number of bytes to commit
+ *
+ * Commit @num bytes of data written to a buffer previously acquired
+ * by seq_buf_get_buf(). To signal an error condition, or that the data
+ * didn't fit in the available space, pass a negative @num value.
+ */
+static inline void seq_buf_commit(struct seq_buf *s, int num)
+{
+	if (num < 0) {
+		seq_buf_set_overflow(s);
+	} else {
+		/* num must be negative on overflow */
+		BUG_ON(s->len + num > s->size);
+		s->len += num;
+	}
+}
+
+/**
+ * seq_buf_pop - pop off the last written character
+ * @s: the seq_buf handle
+ *
+ * Removes the last written character to the seq_buf @s.
+ *
+ * Returns the last character or -1 if it is empty.
+ */
+static inline int seq_buf_pop(struct seq_buf *s)
+{
+	if (!s->len)
+		return -1;
+
+	s->len--;
+	return (unsigned int)s->buffer[s->len];
+}
+
+extern __printf(2, 3)
+int seq_buf_printf(struct seq_buf *s, const char *fmt, ...);
+extern __printf(2, 0)
+int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args);
+extern int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s);
+extern int seq_buf_to_user(struct seq_buf *s, char __user *ubuf,
+			   size_t start, int cnt);
+extern int seq_buf_puts(struct seq_buf *s, const char *str);
+extern int seq_buf_putc(struct seq_buf *s, unsigned char c);
+extern int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len);
+extern int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
+			      unsigned int len);
+extern int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc);
+extern int seq_buf_hex_dump(struct seq_buf *s, const char *prefix_str,
+			    int prefix_type, int rowsize, int groupsize,
+			    const void *buf, size_t len, bool ascii);
+
+#ifdef CONFIG_BINARY_PRINTF
+__printf(2, 0)
+int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary);
+#endif
+
+void seq_buf_do_printk(struct seq_buf *s, const char *lvl);
+
+#endif /* _LINUX_SEQ_BUF_H */