[PATCH bpf-next v3 1/3] kallsyms: add space-efficient lookup in one module

[Viktor Malik <vmalik@xxxxxxxxxx>]

Until now, the only way to look up a symbol in kallsyms of a particular
module was using the "module_kallsyms_lookup_name" function with the
"module:symbol" string passed as a parameter. This syntax often requires
to build the parameter string on stack, needlessly wasting space.

This commit introduces function "kallsyms_lookup_name_in_module" which
takes the module and the symbol names as separate parameters and
therefore allows more space-efficient lookup.

Signed-off-by: Viktor Malik <vmalik@xxxxxxxxxx>
---
 include/linux/module.h   |  7 +++++++
 kernel/module/kallsyms.c | 16 ++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/module.h b/include/linux/module.h
index 35876e89eb93..a06fbcc4013c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -605,6 +605,7 @@ struct module *find_module(const char *name);
 int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 			char *name, char *module_name, int *exported);
 
+unsigned long kallsyms_lookup_name_in_module(const char *module_name, const char *name);
 /* Look for this name: can be of form module:name. */
 unsigned long module_kallsyms_lookup_name(const char *name);
 
@@ -783,6 +784,12 @@ static inline int module_get_kallsym(unsigned int symnum, unsigned long *value,
 	return -ERANGE;
 }
 
+static inline unsigned long kallsyms_lookup_name_in_module(const char *module_name,
+							   const char *name)
+{
+	return 0;
+}
+
 static inline unsigned long module_kallsyms_lookup_name(const char *name)
 {
 	return 0;
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 4523f99b0358..c6c8227c7a45 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -482,6 +482,22 @@ static unsigned long __module_kallsyms_lookup_name(const char *name)
 	return 0;
 }
 
+unsigned long kallsyms_lookup_name_in_module(const char *module_name, const char *name)
+{
+	unsigned long ret;
+	struct module *mod;
+
+	preempt_disable();
+	mod = find_module_all(module_name, strlen(module_name), false);
+	if (mod)
+		ret = find_kallsyms_symbol_value(mod, name);
+	else
+		ret = 0;
+	preempt_enable();
+	return ret;
+
+}
+
 /* Look for this name: can be of form module:name. */
 unsigned long module_kallsyms_lookup_name(const char *name)
 {
-- 
2.38.1