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

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Message-ID: <20250731193126.2eeb21c6@gandalf.local.home>
Date: Thu, 31 Jul 2025 19:31:26 -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>
Subject: [PATCH] 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.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_output.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 0b3db02030a7..b18393d66a7f 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -690,6 +690,12 @@ int trace_print_lat_context(struct trace_iterator *iter)
 }
 
 #ifdef CONFIG_FUNCTION_TRACE_ARGS
+
+static u32 btf_type_int(const struct btf_type *t)
+{
+	return *(u32 *)(t + 1);
+}
+
 void print_function_args(struct trace_seq *s, unsigned long *args,
 			 unsigned long func)
 {
@@ -701,6 +707,8 @@ void print_function_args(struct trace_seq *s, unsigned long *args,
 	struct btf *btf;
 	s32 tid, nr = 0;
 	int a, p, x;
+	int int_data;
+	u16 encode;
 
 	trace_seq_printf(s, "(");
 
@@ -744,7 +752,14 @@ 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);
+			/* Get the INT encodoing */
+			int_data = btf_type_int(t);
+                        encode = BTF_INT_ENCODING(int_data);
+                        /* 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