[PATCH 1/3] perf trace: Introduce kernel symbol beautifier for virtual addresses

[Aaron Tomlin]

Currently, when 'perf trace' formats tracepoint payloads or system call
arguments containing raw kernel virtual addresses (e.g., a work item
function pointer 'work_func_t' in 'workqueue:workqueue_execute_start'),
it prints them as raw hexadecimal values (e.g., 0xffffffff81234567).
This impairs readability when tracing kernel execution flows.

Introduce a dedicated kernel symbol beautifier,
'syscall_arg__scnprintf_ksym' (i.e., SCA_KSYM), to resolve kernel
virtual addresses to human-readable symbol names and offsets
(e.g., 'flush_to_ldisc').

The beautifier looks up the virtual address in the machine kernel maps via
machine__find_kernel_symbol(). If a valid kernel symbol is found, the
symbol name and offset are printed without requiring --libtraceevent; if
the address is zero, "NULL" is rendered; otherwise, it gracefully falls
back to hexadecimal formatting.

Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxxx>
---
 tools/perf/builtin-trace.c       | 24 ++++++++++++++++++++++++
 tools/perf/trace/beauty/beauty.h |  3 +++
 2 files changed, 27 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 5a3e043b5b72..cbc5bdc0cc12 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -749,6 +749,30 @@ size_t syscall_arg__scnprintf_ptr(char *bf, size_t size, struct syscall_arg *arg
 	return syscall_arg__scnprintf_hex(bf, size, arg);
 }
 
+size_t syscall_arg__scnprintf_ksym(char *bf, size_t size, struct syscall_arg *arg)
+{
+	if (arg->val == 0)
+		return scnprintf(bf, size, "NULL");
+
+	if (arg->trace && arg->trace->host) {
+		struct map *map;
+		struct symbol *sym = machine__find_kernel_symbol(arg->trace->host,
+								 arg->val, &map);
+
+		if (sym) {
+			u64 start = map__unmap_ip(map, sym->start);
+			u64 offset = arg->val - start;
+
+			if (offset == 0)
+				return scnprintf(bf, size, "%s", sym->name);
+			return scnprintf(bf, size, "%s+0x%" PRIx64,
+					 sym->name, offset);
+		}
+	}
+
+	return syscall_arg__scnprintf_hex(bf, size, arg);
+}
+
 size_t syscall_arg__scnprintf_int(char *bf, size_t size, struct syscall_arg *arg)
 {
 	return scnprintf(bf, size, "%d", arg->val);
diff --git a/tools/perf/trace/beauty/beauty.h b/tools/perf/trace/beauty/beauty.h
index 58a3206481ae..0f4801c61a5b 100644
--- a/tools/perf/trace/beauty/beauty.h
+++ b/tools/perf/trace/beauty/beauty.h
@@ -160,6 +160,9 @@ size_t syscall_arg__scnprintf_hex(char *bf, size_t size, struct syscall_arg *arg
 size_t syscall_arg__scnprintf_ptr(char *bf, size_t size, struct syscall_arg *arg);
 #define SCA_PTR syscall_arg__scnprintf_ptr
 
+size_t syscall_arg__scnprintf_ksym(char *bf, size_t size, struct syscall_arg *arg);
+#define SCA_KSYM syscall_arg__scnprintf_ksym
+
 size_t syscall_arg__scnprintf_int(char *bf, size_t size, struct syscall_arg *arg);
 #define SCA_INT syscall_arg__scnprintf_int
 
-- 
2.55.0