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authorSteven Rostedt (Google) <rostedt@goodmis.org>2024-03-04 19:13:42 -0500
committerSteven Rostedt (Google) <rostedt@goodmis.org>2024-03-06 13:27:00 -0500
commit6f42249fecb94dfb6514ed241475f748c03d62fb (patch)
treed112fcb0830155a203ba7e5bed61d6cd7bb720f9 /include/linux/trace_seq.h
parent5efd3e2aef91d2d812290dcb25b2058e6f3f532c (diff)
tracing: Limit trace_seq size to just 8K and not depend on architecture PAGE_SIZE
The trace_seq buffer is used to print out entire events. It's typically set to PAGE_SIZE * 2 as there's some events that can be quite large. As a side effect, writes to trace_marker is limited by both the size of the trace_seq buffer as well as the ring buffer's sub-buffer size (which is a power of PAGE_SIZE). By limiting the trace_seq size, it also limits the size of the largest string written to trace_marker. trace_seq does not need to be dependent on PAGE_SIZE like the ring buffer sub-buffers need to be. Hard code it to 8K which is PAGE_SIZE * 2 on most architectures. This will also limit the size of trace_marker on those architectures with greater than 4K PAGE_SIZE. Link: https://lore.kernel.org/all/20240302111244.3a1674be@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240304191342.56fb1087@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sachin Sant <sachinp@linux.ibm.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/trace_seq.h')
-rw-r--r--include/linux/trace_seq.h8
1 files changed, 7 insertions, 1 deletions
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 9ec229dfddaa..1ef95c0287f0 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -9,9 +9,15 @@
/*
* Trace sequences are used to allow a function to call several other functions
* to create a string of data to use.
+ *
+ * Have the trace seq to be 8K which is typically PAGE_SIZE * 2 on
+ * most architectures. The TRACE_SEQ_BUFFER_SIZE (which is
+ * TRACE_SEQ_SIZE minus the other fields of trace_seq), is the
+ * max size the output of a trace event may be.
*/
-#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE * 2 - \
+#define TRACE_SEQ_SIZE 8192
+#define TRACE_SEQ_BUFFER_SIZE (TRACE_SEQ_SIZE - \
(sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int)))
struct trace_seq {