linux-kernel - [PATCH] tracing: Fix compilation warning on arm32

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Message-Id: <20250526013731.1198030-1-pantaixi@huaweicloud.com>
Date: Mon, 26 May 2025 09:37:31 +0800
From: Pan Taixi <pantaixi@...weicloud.com>
To: pantaixi1@...wei.com,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com,
	aha310510@...il.com,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: yeweihua4@...wei.com
Subject: [PATCH] tracing: Fix compilation warning on arm32

On arm32, size_t is defined to be unsigned int, while PAGE_SIZE is
unsigned long. This hence triggers a compilation warning as min()
asserts the type of two operands to be equal. Casting PAGE_SIZE to size_t
solves this issue and works on other target architectures as well.

Compilation warning details:

kernel/trace/trace.c: In function 'tracing_splice_read_pipe':
./include/linux/minmax.h:20:28: warning: comparison of distinct pointer types lacks a cast
  (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
                            ^
./include/linux/minmax.h:26:4: note: in expansion of macro '__typecheck'
   (__typecheck(x, y) && __no_side_effects(x, y))
    ^~~~~~~~~~~

...

kernel/trace/trace.c:6771:8: note: in expansion of macro 'min'
        min((size_t)trace_seq_used(&iter->seq),
        ^~~

Fixes: f5178c41bb43 ("tracing: Fix oob write in trace_seq_to_buffer()")
Signed-off-by: Pan Taixi <pantaixi@...weicloud.com>
---
 kernel/trace/trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5b8db27fb6ef..766cb3cd254e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6824,7 +6824,7 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
 		ret = trace_seq_to_buffer(&iter->seq,
 					  page_address(spd.pages[i]),
 					  min((size_t)trace_seq_used(&iter->seq),
-						  PAGE_SIZE));
+						  (size_t)PAGE_SIZE));
 		if (ret < 0) {
 			__free_page(spd.pages[i]);
 			break;
-- 
2.34.1