[PATCH v2 1/2] modules: Add __module_build_id() to find module by build_id

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add __module_build_id() to find module by build_id. This also makes
module::build_id available with CONFIG_MODULE_BUILD_ID kconfig.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 include/linux/module.h   |    8 +++++++-
 kernel/module/Kconfig    |    3 +++
 kernel/module/kallsyms.c |    4 ++--
 kernel/module/main.c     |   29 +++++++++++++++++++++++++++++
 lib/Kconfig.debug        |    1 +
 5 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index b3a643435357..e181056d6af6 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -416,7 +416,7 @@ struct module {
 	/* Unique handle for this module */
 	char name[MODULE_NAME_LEN];
 
-#ifdef CONFIG_STACKTRACE_BUILD_ID
+#ifdef CONFIG_MODULE_BUILD_ID
 	/* Module build ID */
 	unsigned char build_id[BUILD_ID_SIZE_MAX];
 #endif
@@ -622,6 +622,7 @@ static inline bool module_is_coming(struct module *mod)
 
 struct module *__module_text_address(unsigned long addr);
 struct module *__module_address(unsigned long addr);
+struct module *__module_build_id(unsigned char *build_id, int size);
 bool is_module_address(unsigned long addr);
 bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr);
 bool is_module_percpu_address(unsigned long addr);
@@ -791,6 +792,11 @@ static inline struct module *__module_text_address(unsigned long addr)
 	return NULL;
 }
 
+static inline struct module *__module_build_id(unsigned char *build_id, int size)
+{
+	return NULL;
+}
+
 static inline bool is_module_address(unsigned long addr)
 {
 	return false;
diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 7b329057997a..5e81dea1afea 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -26,6 +26,9 @@ if MODULES
 config MODULE_DEBUGFS
 	bool
 
+config MODULE_BUILD_ID
+	bool
+
 config MODULE_DEBUG
 	bool "Module debugging"
 	depends on DEBUG_FS
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index bf65e0c3c86f..98f2661c1da8 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -224,7 +224,7 @@ void add_kallsyms(struct module *mod, const struct load_info *info)
 	mod->core_kallsyms.num_symtab = ndst;
 }
 
-#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+#if IS_ENABLED(CONFIG_MODULE_BUILD_ID)
 void init_build_id(struct module *mod, const struct load_info *info)
 {
 	const Elf_Shdr *sechdr;
@@ -338,7 +338,7 @@ int module_address_lookup(unsigned long addr,
 		if (modname)
 			*modname = mod->name;
 		if (modbuildid) {
-#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+#if IS_ENABLED(CONFIG_MODULE_BUILD_ID)
 			*modbuildid = mod->build_id;
 #else
 			*modbuildid = NULL;
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 5399c182b3cb..fca9b6a692e3 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3746,6 +3746,35 @@ struct module *__module_text_address(unsigned long addr)
 	return mod;
 }
 
+/**
+ * __module_build_id() - get the module whose build_id start with an array.
+ * @build_id: the first part of the build_id.
+ * @size: the size of @build_id.
+ *
+ * Must be called with preempt disabled or module mutex held so that
+ * module doesn't get freed during this.
+ */
+struct module *__module_build_id(unsigned char *build_id, int size)
+{
+#ifdef CONFIG_MODULE_BUILD_ID
+	struct module *mod;
+
+	if (size < 0)
+		return NULL;
+
+	if (size > BUILD_ID_SIZE_MAX)
+		size = BUILD_ID_SIZE_MAX;
+
+	list_for_each_entry_rcu(mod, &modules, list) {
+		if (mod->state == MODULE_STATE_UNFORMED)
+			continue;
+		if (!memcmp(mod->build_id, build_id, size))
+			return mod;
+	}
+#endif
+	return NULL;
+}
+
 /* Don't grab lock, we're oopsing. */
 void print_modules(void)
 {
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cf2a41dc7682..2d3a2f656a86 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -38,6 +38,7 @@ config PRINTK_CALLER
 config STACKTRACE_BUILD_ID
 	bool "Show build ID information in stacktraces"
 	depends on PRINTK
+	select MODULE_BUILD_ID if MODULES
 	help
 	  Selecting this option adds build ID information for symbols in
 	  stacktraces printed with the printk format '%p[SR]b'.