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From: Steven Rostedt <rostedt@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Elijah Wright <git@elijahs.space>
Subject: [for-next][PATCH 05/11] tracing: Move buffer in trace_seq to end of struct
Date: Tue, 30 Sep 2025 13:01:40 -0400	[thread overview]
Message-ID: <20250930170302.037046621@kernel.org> (raw)
In-Reply-To: 20250930170135.285740909@kernel.org

From: Elijah Wright <git@elijahs.space>

TRACE_SEQ_BUFFER_SIZE is dependent on the architecture for its size. on 64-bit
systems, it is 8148 bytes. forced 8-byte alignment in size_t and seq_buf means
that trace_seq is 8200 bytes on 64-bit systems. moving the buffer to the end
of the struct fixes the issue. there shouldn't be any side effects, i.e.
pointer arithmetic on trace_seq

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250821053917.23301-1-git@elijahs.space
Signed-off-by: Elijah Wright <git@elijahs.space>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/linux/trace_seq.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index a93ed5ac3226..557780fe1c77 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -21,10 +21,10 @@
 	(sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int)))
 
 struct trace_seq {
-	char			buffer[TRACE_SEQ_BUFFER_SIZE];
 	struct seq_buf		seq;
 	size_t			readpos;
 	int			full;
+	char                    buffer[TRACE_SEQ_BUFFER_SIZE];
 };
 
 static inline void
-- 
2.50.1



  parent reply	other threads:[~2025-09-30 17:01 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-30 17:01 [for-next][PATCH 00/11] tracing: Updates for v6.18 Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 01/11] tracing: Replace syscall RCU pointer assignment with READ/WRITE_ONCE() Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 02/11] tracing: Have syscall trace events show "0x" for values greater than 10 Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 03/11] tracing: Use vmalloc_array() to improve code Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 04/11] tracing/osnoise: Use for_each_online_cpu() instead of for_each_cpu() Steven Rostedt
2025-09-30 17:01 ` Steven Rostedt [this message]
2025-09-30 17:01 ` [for-next][PATCH 06/11] tracing: Remove redundant 0 value initialization Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 07/11] tracing: replace use of system_wq with system_percpu_wq Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 08/11] tracing/osnoise: Replace kmalloc() + copy_from_user() with memdup_user() Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 09/11] ftrace: Fix softlockup in ftrace_module_enable Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 10/11] tracing: Ensure optimized hashing works Steven Rostedt
2025-09-30 17:01 ` [for-next][PATCH 11/11] tracing: Fix lock imbalance in s_start() memory allocation failure path Steven Rostedt

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