[RFC PATCH] gcov: add basic gcov_info validation to gcov initialization

[Luis Henriques]

Add a basic gcov_info struct validation helper to gcc to ensure we have
sane from the compiler.

Signed-off-by: Luis Henriques <lhenriques@xxxxxxx>
---
Hi!

I know this won't really validate the gcov_info struct, but it will at
least prevent kernel crashes in simple scenarios (such as the one I'm
seeing with gcc 9.3.1).

Cheers,
--
Luis

 kernel/gcov/gcc_4_7.c  | 8 ++++++++
 kernel/gcov/gcc_base.c | 5 +++++
 kernel/gcov/gcov.h     | 1 +
 3 files changed, 14 insertions(+)

diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
index 460c12b7dfea..028d9b94463d 100644
--- a/kernel/gcov/gcc_4_7.c
+++ b/kernel/gcov/gcc_4_7.c
@@ -126,6 +126,14 @@ struct gcov_info *gcov_info_next(struct gcov_info *info)
 	return info->next;
 }
 
+bool gcov_info_is_valid(struct gcov_info *info)
+{
+	if (!info || !info->functions)
+		return false;
+
+	return true;
+}
+
 /**
  * gcov_info_link - link/add profiling data set to the list
  * @info: profiling data set
diff --git a/kernel/gcov/gcc_base.c b/kernel/gcov/gcc_base.c
index 3cf736b9f880..3e02a89f69b6 100644
--- a/kernel/gcov/gcc_base.c
+++ b/kernel/gcov/gcc_base.c
@@ -13,6 +13,11 @@ void __gcov_init(struct gcov_info *info)
 {
 	static unsigned int gcov_version;
 
+	if (!gcov_info_is_valid(info)) {
+		pr_err_once("Invalid gcov_info structure\n");
+		return;
+	}
+
 	mutex_lock(&gcov_lock);
 	if (gcov_version == 0) {
 		gcov_version = gcov_info_version(info);
diff --git a/kernel/gcov/gcov.h b/kernel/gcov/gcov.h
index 912b8ea01d33..4b3d924c2031 100644
--- a/kernel/gcov/gcov.h
+++ b/kernel/gcov/gcov.h
@@ -45,6 +45,7 @@ struct gcov_info;
 const char *gcov_info_filename(struct gcov_info *info);
 unsigned int gcov_info_version(struct gcov_info *info);
 struct gcov_info *gcov_info_next(struct gcov_info *info);
+bool gcov_info_is_valid(struct gcov_info *info);
 void gcov_info_link(struct gcov_info *info);
 void gcov_info_unlink(struct gcov_info *prev, struct gcov_info *info);
 bool gcov_info_within_module(struct gcov_info *info, struct module *mod);