block alloc: add validations around cache_entry lifecyle

Add an option (controlled by an environment variable) perform extra
validations on mem_pool allocated cache entries. When set:

  1) Invalidate cache_entry memory when discarding cache_entry.

  2) When discarding index_state struct, verify that all cache_entries
     were allocated from expected mem_pool.

  3) When discarding mem_pools, invalidate mem_pool memory.

This should provide extra checks that mem_pools and their allocated
cache_entries are being used as expected.

Signed-off-by: Jameson Miller <jamill@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index c1c7e9e..a3334a7 100644
--- a/cache.h
+++ b/cache.h
@@ -381,6 +381,12 @@ struct cache_entry *make_empty_transient_cache_entry(size_t name_len);
 void discard_cache_entry(struct cache_entry *ce);
 
 /*
+ * Check configuration if we should perform extra validation on cache
+ * entries.
+ */
+int should_validate_cache_entries(void);
+
+/*
  * Duplicate a cache_entry. Allocate memory for the new entry from a
  * memory_pool. Takes into account cache_entry fields that are meant
  * for managing the underlying memory allocation of the cache_entry.