linux-kernel - [PATCH v2 02/27] fgraph: Use BUILD_BUG_ON() to make sure we have structures divisible by long

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Date: Sat, 01 Jun 2024 23:37:46 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>,
 Florent Revest <revest@...omium.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>,
 bpf <bpf@...r.kernel.org>,
 Sven Schnelle <svens@...ux.ibm.com>,
 Alexei Starovoitov <ast@...nel.org>,
 Jiri Olsa <jolsa@...nel.org>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Alan Maguire <alan.maguire@...cle.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Guo Ren <guoren@...nel.org>
Subject: [PATCH v2 02/27] fgraph: Use BUILD_BUG_ON() to make sure we have structures divisible
 by long

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

Instead of using "ALIGN()", use BUILD_BUG_ON() as the structures should
always be divisible by sizeof(long).

Co-developed with Masami Hiramatsu:
Link: https://lore.kernel.org/linux-trace-kernel/171509093949.162236.14518699447151894536.stgit@devnote2
Link: http://lkml.kernel.org/r/20190524111144.GI2589@hirez.programming.kicks-ass.net

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/fgraph.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index c62e6db718a0..fdb206aeffe3 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -33,7 +33,7 @@
  * SHADOW_STACK_MAX_OFFSET: The max offset of the stack for a new frame to be added
  */
 #define FGRAPH_FRAME_SIZE	sizeof(struct ftrace_ret_stack)
-#define FGRAPH_FRAME_OFFSET	(ALIGN(FGRAPH_FRAME_SIZE, sizeof(long)) / sizeof(long))
+#define FGRAPH_FRAME_OFFSET	DIV_ROUND_UP(FGRAPH_FRAME_SIZE, sizeof(long))
 #define SHADOW_STACK_SIZE (PAGE_SIZE)
 #define SHADOW_STACK_OFFSET			\
 	(ALIGN(SHADOW_STACK_SIZE, sizeof(long)) / sizeof(long))
@@ -103,6 +103,8 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
 	if (!current->ret_stack)
 		return -EBUSY;
 
+	BUILD_BUG_ON(SHADOW_STACK_SIZE % sizeof(long));
+
 	/*
 	 * We must make sure the ret_stack is tested before we read
 	 * anything else.
@@ -326,6 +328,8 @@ ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
 {
 	int index = task->curr_ret_stack;
 
+	BUILD_BUG_ON(FGRAPH_FRAME_SIZE % sizeof(long));
+
 	index -= FGRAPH_FRAME_OFFSET * (idx + 1);
 	if (index < 0)
 		return NULL;
-- 
2.43.0