linux-kernel - [PATCH v3] tracing: Have unsigned int function args displayed as hexadecimal

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Message-ID: <20250801165601.7770d65c@gandalf.local.home>
Date: Fri, 1 Aug 2025 16:56:01 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, bpf@...r.kernel.org, Douglas Raillard 
 <douglas.raillard@....com>, Yonghong Song <yonghong.song@...ux.dev>, Martin
 KaFai Lau <martin.lau@...ux.dev>
Subject: [PATCH v3] tracing: Have unsigned int function args displayed as
 hexadecimal

From aff4ac7a3e0bc7e7db72a0fae52f1a8b06e415f0 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <rostedt@...dmis.org>
Date: Fri, 1 Aug 2025 11:14:53 -0400
Subject: [PATCH] tracing: Have unsigned int function args displayed as
 hexadecimal

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)

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