+ kallsyms-cleanup-code-for-appending-the-module-buildid.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kallsyms: cleanup code for appending the module buildid
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kallsyms-cleanup-code-for-appending-the-module-buildid.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kallsyms-cleanup-code-for-appending-the-module-buildid.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Petr Mladek <pmladek@suse.com>
Subject: kallsyms: cleanup code for appending the module buildid
Date: Fri, 28 Nov 2025 14:59:17 +0100

Put the code for appending the optional "buildid" into a helper function,
It makes __sprint_symbol() better readable.

Also print a warning when the "modname" is set and the "buildid" isn't. 
It might catch a situation when some lookup function in
kallsyms_lookup_buildid() does not handle the "buildid".

Use pr_*_once() to avoid an infinite recursion when the function is called
from printk().  The recursion is rather theoretical but better be on the
safe side.

Link: https://lkml.kernel.org/r/20251128135920.217303-5-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Aaron Tomlin <atomlin@atomlin.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkman <daniel@iogearbox.net>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Luis Chamberalin <mcgrof@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Petr Pavlu <petr.pavlu@suse.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/kallsyms.c |   42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

--- a/kernel/kallsyms.c~kallsyms-cleanup-code-for-appending-the-module-buildid
+++ a/kernel/kallsyms.c
@@ -435,6 +435,37 @@ int lookup_symbol_name(unsigned long add
 	return lookup_module_symbol_name(addr, symname);
 }
 
+#ifdef CONFIG_STACKTRACE_BUILD_ID
+
+static int append_buildid(char *buffer,  const char *modname,
+			  const unsigned char *buildid)
+{
+	if (!modname)
+		return 0;
+
+	if (!buildid) {
+		pr_warn_once("Undefined buildid for the module %s\n", modname);
+		return 0;
+	}
+
+	/* build ID should match length of sprintf */
+#ifdef CONFIG_MODULES
+	static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
+#endif
+
+	return sprintf(buffer, " %20phN", buildid);
+}
+
+#else /* CONFIG_STACKTRACE_BUILD_ID */
+
+static int append_buildid(char *buffer,   const char *modname,
+			  const unsigned char *buildid)
+{
+	return 0;
+}
+
+#endif /* CONFIG_STACKTRACE_BUILD_ID */
+
 /* Look up a kernel symbol and return it in a text buffer. */
 static int __sprint_symbol(char *buffer, unsigned long address,
 			   int symbol_offset, int add_offset, int add_buildid)
@@ -457,15 +488,8 @@ static int __sprint_symbol(char *buffer,
 
 	if (modname) {
 		len += sprintf(buffer + len, " [%s", modname);
-#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
-		if (add_buildid && buildid) {
-			/* build ID should match length of sprintf */
-#if IS_ENABLED(CONFIG_MODULES)
-			static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
-#endif
-			len += sprintf(buffer + len, " %20phN", buildid);
-		}
-#endif
+		if (add_buildid)
+			len += append_buildid(buffer + len, modname, buildid);
 		len += sprintf(buffer + len, "]");
 	}
 
_

Patches currently in -mm which might be from pmladek@suse.com are

kallsyms-clean-up-namebuf-initialization-in-kallsyms_lookup_buildid.patch
kallsyms-clean-up-modname-and-modbuildid-initialization-in-kallsyms_lookup_buildid.patch
module-add-helper-function-for-reading-module_buildid.patch
kallsyms-cleanup-code-for-appending-the-module-buildid.patch
kallsyms-bpf-rename-__bpf_address_lookup-to-bpf_address_lookup.patch
kallsyms-ftrace-set-module-buildid-in-ftrace_mod_address_lookup.patch
kallsyms-prevent-module-removal-when-printing-module-name-and-buildid.patch