This is a note to let you know that I've just added the patch titled
tracing: Move readpos from seq_buf to trace_seq
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-move-readpos-from-seq_buf-to-trace_seq.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fa373a3627724c64381e9d426f870db77f7e6846
Author: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Date: Fri Oct 20 04:35:45 2023 +0100
tracing: Move readpos from seq_buf to trace_seq
[ Upstream commit d0ed46b60396cfa7e0056f55e1ce0b43c7db57b6 ]
To make seq_buf more lightweight as a string buf, move the readpos member
from seq_buf to its container, trace_seq. That puts the responsibility
of maintaining the readpos entirely in the tracing code. If some future
users want to package up the readpos with a seq_buf, we can define a
new struct then.
Link: https://lore.kernel.org/linux-trace-kernel/20231020033545.2587554-2-willy@xxxxxxxxxxxxx
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Justin Stitt <justinstitt@xxxxxxxxxx>
Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Stable-dep-of: afd2627f727b ("tracing: Check "%s" dereference via the field and not the TP_printk format")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index 515d7fcb9634..a0fb013cebdf 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -14,19 +14,16 @@
* @buffer: pointer to the buffer
* @size: size of the buffer
* @len: the amount of data inside the buffer
- * @readpos: The next position to read in the buffer.
*/
struct seq_buf {
char *buffer;
size_t size;
size_t len;
- loff_t readpos;
};
static inline void seq_buf_clear(struct seq_buf *s)
{
s->len = 0;
- s->readpos = 0;
}
static inline void
@@ -143,7 +140,7 @@ 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,
- int cnt);
+ 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);
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 6be92bf559fe..3691e0e76a1a 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -14,6 +14,7 @@
struct trace_seq {
char buffer[PAGE_SIZE];
struct seq_buf seq;
+ size_t readpos;
int full;
};
@@ -22,6 +23,7 @@ trace_seq_init(struct trace_seq *s)
{
seq_buf_init(&s->seq, s->buffer, PAGE_SIZE);
s->full = 0;
+ s->readpos = 0;
}
/**
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 220903117c51..83f6ef4d7419 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1731,15 +1731,15 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
{
int len;
- if (trace_seq_used(s) <= s->seq.readpos)
+ if (trace_seq_used(s) <= s->readpos)
return -EBUSY;
- len = trace_seq_used(s) - s->seq.readpos;
+ len = trace_seq_used(s) - s->readpos;
if (cnt > len)
cnt = len;
- memcpy(buf, s->buffer + s->seq.readpos, cnt);
+ memcpy(buf, s->buffer + s->readpos, cnt);
- s->seq.readpos += cnt;
+ s->readpos += cnt;
return cnt;
}
@@ -7011,7 +7011,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
/* Now copy what we have to the user */
sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
- if (iter->seq.seq.readpos >= trace_seq_used(&iter->seq))
+ if (iter->seq.readpos >= trace_seq_used(&iter->seq))
trace_seq_init(&iter->seq);
/*
diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
index bac06ee3b98b..7be97229ddf8 100644
--- a/kernel/trace/trace_seq.c
+++ b/kernel/trace/trace_seq.c
@@ -370,8 +370,12 @@ EXPORT_SYMBOL_GPL(trace_seq_path);
*/
int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
{
+ int ret;
__trace_seq_init(s);
- return seq_buf_to_user(&s->seq, ubuf, cnt);
+ ret = seq_buf_to_user(&s->seq, ubuf, s->readpos, cnt);
+ if (ret > 0)
+ s->readpos += ret;
+ return ret;
}
EXPORT_SYMBOL_GPL(trace_seq_to_user);
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 45c450f423fa..b7477aefff53 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -324,23 +324,24 @@ int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
* seq_buf_to_user - copy the sequence buffer to user space
* @s: seq_buf descriptor
* @ubuf: The userspace memory location to copy to
+ * @start: The first byte in the buffer to copy
* @cnt: The amount to copy
*
* Copies the sequence buffer into the userspace memory pointed to
- * by @ubuf. It starts from the last read position (@s->readpos)
- * and writes up to @cnt characters or till it reaches the end of
- * the content in the buffer (@s->len), which ever comes first.
+ * by @ubuf. It starts from @start and writes up to @cnt characters
+ * or until it reaches the end of the content in the buffer (@s->len),
+ * whichever comes first.
*
* On success, it returns a positive number of the number of bytes
* it copied.
*
* On failure it returns -EBUSY if all of the content in the
* sequence has been already read, which includes nothing in the
- * sequence (@s->len == @s->readpos).
+ * sequence (@s->len == @start).
*
* Returns -EFAULT if the copy to userspace fails.
*/
-int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
+int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, size_t start, int cnt)
{
int len;
int ret;
@@ -350,20 +351,17 @@ int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
len = seq_buf_used(s);
- if (len <= s->readpos)
+ if (len <= start)
return -EBUSY;
- len -= s->readpos;
+ len -= start;
if (cnt > len)
cnt = len;
- ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
+ ret = copy_to_user(ubuf, s->buffer + start, cnt);
if (ret == cnt)
return -EFAULT;
- cnt -= ret;
-
- s->readpos += cnt;
- return cnt;
+ return cnt - ret;
}
/**
