diff options
| -rw-r--r-- | scripts/gcc-plugins/randomize_layout_plugin.c | 63 |
1 files changed, 59 insertions, 4 deletions
diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c index ff65a4f87f24..1e66f45fe29b 100644 --- a/scripts/gcc-plugins/randomize_layout_plugin.c +++ b/scripts/gcc-plugins/randomize_layout_plugin.c @@ -22,7 +22,7 @@ #define ORIG_TYPE_NAME(node) \ (TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous") -#define INFORM(loc, msg, ...) inform(loc, "randstruct: " msg, ##__VA_ARGS__) +#define INFORM(loc, msg, ...) warning_at(loc, 0, "randstruct: " msg, ##__VA_ARGS__) #define MISMATCH(loc, how, ...) INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__) __visible int plugin_is_GPL_compatible; @@ -699,6 +699,63 @@ static void handle_local_var_initializers(void) } /* + * Does @container reach a field of type @member_type by a chain of + * by-value members? That is the relationship container_of() expresses -- + * its @member argument may be a dotted path, e.g. + * container_of(inode, struct ceph_inode_info, netfs.inode) -- so a cast + * from @member_type * to @container * is legitimate rather than a + * layout-confusing one. + * + * container_of() used to leave a "void *__mptr" temporary behind, and this + * pass recognised such casts by that name. Commit f9e7a7564834 + * ("container_of: remove local __mptr variable") removed it to stop nested + * container_of() shadowing itself, and the cast now folds to a bare SSA + * copy when the member sits at offset 0, leaving nothing syntactic to key + * on. Match the type relationship instead. + * + * The depth bound keeps this cheap; container_of() paths are one or two + * members deep in practice. + */ +#define CONTAINER_OF_MAX_DEPTH 4 + +static bool is_container_of_cast(const_tree container, const_tree member_type, + int depth) +{ + const_tree field; + + if (container == NULL_TREE || depth > CONTAINER_OF_MAX_DEPTH) + return false; + + if (TREE_CODE(container) != RECORD_TYPE && + TREE_CODE(container) != UNION_TYPE) + return false; + + for (field = TYPE_FIELDS(container); field; field = DECL_CHAIN(field)) { + const_tree field_type; + + if (TREE_CODE(field) != FIELD_DECL) + continue; + + /* + * Only a member at offset 0 can reach here: for any other + * offset container_of()'s subtraction survives folding, the + * cast's rhs stays void *, and the caller skipped it above. + */ + if (!integer_zerop(byte_position(field))) + continue; + + field_type = TYPE_MAIN_VARIANT(TREE_TYPE(field)); + if (field_type == member_type) + return true; + + if (is_container_of_cast(field_type, member_type, depth + 1)) + return true; + } + + return false; +} + +/* * iterate over all statements to find "bad" casts: * those where the address of the start of a structure is cast * to a pointer of a structure of a different type, or a @@ -799,10 +856,8 @@ static unsigned int find_bad_casts_execute(void) #endif MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type); } else { - const_tree ssa_name_var = SSA_NAME_VAR(rhs1); /* skip bogus type casts introduced by container_of */ - if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && - !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr")) + if (is_container_of_cast(ptr_lhs_type, ptr_rhs_type, 0)) continue; #ifndef __DEBUG_PLUGIN if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type))) |