| Message ID | 20240304223433.4ba47dff@gandalf.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 095fe4891282be510af0db1b03587b512c0de31d |
| Headers | show |
| Series | [v2] tracing: Limit trace_marker writes to just 4K | expand |
On 2024-03-04 22:34, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > Limit the max print event of trace_marker to just 4K string size. This must > also be less than the amount that can be held by a trace_seq along with > the text that is before the output (like the task name, PID, CPU, state, > etc). As trace_seq is made to handle large events (some greater than 4K). > Make the max size of a trace_marker write event be 4K which is guaranteed > to fit in the trace_seq buffer. > > Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> From my perspective I only attempted to clarify the point Linus made about limiting the trace_marker input to 4kB. Feel adapt the Suggested-by tag accordingly. Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Thanks, Mathieu > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > Changes since v1: https://lore.kernel.org/linux-trace-kernel/20240304192710.4c99677c@gandalf.local.home/ > > - Just make the max limit 4K and not half of the trace_seq size. > The trace_seq is already made to handle events greater than 4k. > > kernel/trace/trace.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 8198bfc54b58..d16b95ca58a7 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -7293,6 +7293,8 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp) > return 0; > } > > +#define TRACE_MARKER_MAX_SIZE 4096 > + > static ssize_t > tracing_mark_write(struct file *filp, const char __user *ubuf, > size_t cnt, loff_t *fpos) > @@ -7320,6 +7322,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > if ((ssize_t)cnt < 0) > return -EINVAL; > > + if (cnt > TRACE_MARKER_MAX_SIZE) > + cnt = TRACE_MARKER_MAX_SIZE; > + > meta_size = sizeof(*entry) + 2; /* add '\0' and possible '\n' */ > again: > size = cnt + meta_size; > @@ -7328,11 +7333,6 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > if (cnt < FAULTED_SIZE) > size += FAULTED_SIZE - cnt; > > - if (size > TRACE_SEQ_BUFFER_SIZE) { > - cnt -= size - TRACE_SEQ_BUFFER_SIZE; > - goto again; > - } > - > buffer = tr->array_buffer.buffer; > event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, > tracing_gen_ctx());
On Mon, 4 Mar 2024 22:34:33 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > Limit the max print event of trace_marker to just 4K string size. This must > also be less than the amount that can be held by a trace_seq along with > the text that is before the output (like the task name, PID, CPU, state, > etc). As trace_seq is made to handle large events (some greater than 4K). > Make the max size of a trace_marker write event be 4K which is guaranteed > to fit in the trace_seq buffer. > > Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> This looks good to me. Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thank you, > --- > Changes since v1: https://lore.kernel.org/linux-trace-kernel/20240304192710.4c99677c@gandalf.local.home/ > > - Just make the max limit 4K and not half of the trace_seq size. > The trace_seq is already made to handle events greater than 4k. > > kernel/trace/trace.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 8198bfc54b58..d16b95ca58a7 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -7293,6 +7293,8 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp) > return 0; > } > > +#define TRACE_MARKER_MAX_SIZE 4096 > + > static ssize_t > tracing_mark_write(struct file *filp, const char __user *ubuf, > size_t cnt, loff_t *fpos) > @@ -7320,6 +7322,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > if ((ssize_t)cnt < 0) > return -EINVAL; > > + if (cnt > TRACE_MARKER_MAX_SIZE) > + cnt = TRACE_MARKER_MAX_SIZE; > + > meta_size = sizeof(*entry) + 2; /* add '\0' and possible '\n' */ > again: > size = cnt + meta_size; > @@ -7328,11 +7333,6 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > if (cnt < FAULTED_SIZE) > size += FAULTED_SIZE - cnt; > > - if (size > TRACE_SEQ_BUFFER_SIZE) { > - cnt -= size - TRACE_SEQ_BUFFER_SIZE; > - goto again; > - } > - > buffer = tr->array_buffer.buffer; > event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, > tracing_gen_ctx()); > -- > 2.43.0 >
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8198bfc54b58..d16b95ca58a7 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7293,6 +7293,8 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp) return 0; } +#define TRACE_MARKER_MAX_SIZE 4096 + static ssize_t tracing_mark_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *fpos) @@ -7320,6 +7322,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if ((ssize_t)cnt < 0) return -EINVAL; + if (cnt > TRACE_MARKER_MAX_SIZE) + cnt = TRACE_MARKER_MAX_SIZE; + meta_size = sizeof(*entry) + 2; /* add '\0' and possible '\n' */ again: size = cnt + meta_size; @@ -7328,11 +7333,6 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (cnt < FAULTED_SIZE) size += FAULTED_SIZE - cnt; - if (size > TRACE_SEQ_BUFFER_SIZE) { - cnt -= size - TRACE_SEQ_BUFFER_SIZE; - goto again; - } - buffer = tr->array_buffer.buffer; event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, tracing_gen_ctx());