linux-kernel - [for-next][PATCH 6/6] tracing: Have unsigned int function args displayed as hexadecimal

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Message-ID: <20250802162829.867162195@kernel.org>
Date: Sat, 02 Aug 2025 12:27:40 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Tomas Glozar <tglozar@...hat.com>,
 John Kacur <jkacur@...hat.com>,
 Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Douglas Raillard <douglas.raillard@....com>,
 Martin KaFai Lau <martin.lau@...ux.dev>,
 Yonghong Song <yonghong.song@...ux.dev>
Subject: [for-next][PATCH 6/6] tracing: Have unsigned int function args displayed as hexadecimal

From: Steven Rostedt <rostedt@...dmis.org>

Most function arguments that are passed in as unsigned int or unsigned
long are better displayed as hexadecimal than normal integer. For example,
the functions:

static void __create_object(unsigned long ptr, size_t size,
				int min_count, gfp_t gfp, unsigned int objflags);

static bool stack_access_ok(struct unwind_state *state, unsigned long _addr,
			    size_t len);

void __local_bh_disable_ip(unsigned long ip, unsigned int cnt);

Show up in the trace as:

    __create_object(ptr=-131387050520576, size=4096, min_count=1, gfp=3264, objflags=0) <-kmem_cache_alloc_noprof
    stack_access_ok(state=0xffffc9000233fc98, _addr=-60473102566256, len=8) <-unwind_next_frame
    __local_bh_disable_ip(ip=-2127311112, cnt=256) <-handle_softirqs

Instead, by displaying unsigned as hexadecimal, they look more like this:

    __create_object(ptr=0xffff8881028d2080, size=0x280, min_count=1, gfp=0x82820, objflags=0x0) <-kmem_cache_alloc_node_noprof
    stack_access_ok(state=0xffffc90000003938, _addr=0xffffc90000003930, len=0x8) <-unwind_next_frame
    __local_bh_disable_ip(ip=0xffffffff8133cef8, cnt=0x100) <-handle_softirqs

Which is much easier to understand as most unsigned longs are usually just
pointers. Even the "unsigned int cnt" in __local_bh_disable_ip() looks
better as hexadecimal as a lot of flags are passed as unsigned.

Changes since v2: https://lore.kernel.org/20250801111453.01502861@gandalf.local.home

- Use btf_int_encoding() instead of open coding it (Martin KaFai Lau)

Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Douglas Raillard <douglas.raillard@....com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Link: https://lore.kernel.org/20250801165601.7770d65c@gandalf.local.home
Acked-by: Yonghong Song <yonghong.song@...ux.dev>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_output.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 0b3db02030a7..97db0b0ccf3e 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -701,6 +701,7 @@ void print_function_args(struct trace_seq *s, unsigned long *args,
 	struct btf *btf;
 	s32 tid, nr = 0;
 	int a, p, x;
+	u16 encode;
 
 	trace_seq_printf(s, "(");
 
@@ -744,7 +745,12 @@ void print_function_args(struct trace_seq *s, unsigned long *args,
 			trace_seq_printf(s, "0x%lx", arg);
 			break;
 		case BTF_KIND_INT:
-			trace_seq_printf(s, "%ld", arg);
+			encode = btf_int_encoding(t);
+			/* Print unsigned ints as hex */
+			if (encode & BTF_INT_SIGNED)
+				trace_seq_printf(s, "%ld", arg);
+			else
+				trace_seq_printf(s, "0x%lx", arg);
 			break;
 		case BTF_KIND_ENUM:
 			trace_seq_printf(s, "%ld", arg);
-- 
2.47.2