[for-linus][PATCH] tracing: Fix unused tracepoints when module uses only exported ones

[Steven Rostedt <rostedt@goodmis.org>]

tracing fix for v6.19:

- Fix unused tracepoint build for modules only using exported tracepoints

  The tracepoint-update.c code that looks for unused tracepoints expects
  if tracepoints are used then it will have tracepoints defined. If
  not, it errors out which fails the build.

  In most cases this the way things work. A tracepoint can't be used if
  it is not defined. There is one exception. If a module only uses
  tracepoints that are defined in other modules or the vmlinux proper,
  where the tracepoints are exported. In this case, the
  tracepoint-update.c code thinks tracepoints are used but not defined
  and errors out, failing the build.

  When tracepoint-update.c detects this case, if it is a module that is
  being processed, exit out normally as it is a legitimate case.

  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace/fixes

Head SHA1: 0c5d252a7cb0073f475be389a523de2095973dd2


Steven Rostedt (1):
      tracing: Fix unused tracepoints when module uses only exported ones

----
 scripts/tracepoint-update.c | 3 +++
 1 file changed, 3 insertions(+)
---------------------------
commit 0c5d252a7cb0073f475be389a523de2095973dd2
Author: Steven Rostedt <rostedt@goodmis.org>
Date:   Mon Dec 8 08:53:36 2025 -0500

    tracing: Fix unused tracepoints when module uses only exported ones
    
    Building the KVM intel module failed to build with UT=1:
    
    no __tracepoint_strings in file: arch/x86/kvm/kvm-intel.o
    make[3]: *** [/work/git/test-linux.git/scripts/Makefile.modfinal:62: arch/x86/kvm/kvm-intel.ko] Error 1
    
    The reason is that the module only uses the tracepoints defined and
    exported by the main kvm module. The tracepoint-udpate.c code fails the
    build if a tracepoint is used, but there's no tracepoints defined. But
    this is acceptable in modules if the tracepoints is defined in the vmlinux
    proper or another module and exported.
    
    Do not fail to build if a tracepoint is used but no tracepoints are
    defined if the code is a module. This should still never happen for the
    vmlinux itself.
    
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Cc: Masahiro Yamada <masahiroy@kernel.org>
    Link: https://patch.msgid.link/20251208085336.6658743c@debian
    Fixes: e30f8e61e2518 ("tracing: Add a tracepoint verification check at build time")
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/scripts/tracepoint-update.c b/scripts/tracepoint-update.c
index 7f7d90df14ce..90046aedc97b 100644
--- a/scripts/tracepoint-update.c
+++ b/scripts/tracepoint-update.c
@@ -210,6 +210,9 @@ static int process_tracepoints(bool mod, void *addr, const char *fname)
 	}
 
 	if (!tracepoint_data_sec) {
+		/* A module may reference only exported tracepoints */
+		if (mod)
+			return 0;
 		fprintf(stderr,	"no __tracepoint_strings in file: %s\n", fname);
 		return -1;
 	}