module: preserve Elf information for livepatch modules

For livepatch modules, copy Elf section, symbol, and string information
from the load_info struct in the module loader. Persist copies of the
original symbol table and string table.

Livepatch manages its own relocation sections in order to reuse module
loader code to write relocations. Livepatch modules must preserve Elf
information such as section indices in order to apply livepatch relocation
sections using the module loader's apply_relocate_add() function.

In order to apply livepatch relocation sections, livepatch modules must
keep a complete copy of their original symbol table in memory. Normally, a
stripped down copy of a module's symbol table (containing only "core"
symbols) is made available through module->core_symtab. But for livepatch
modules, the symbol table copied into memory on module load must be exactly
the same as the symbol table produced when the patch module was compiled.
This is because the relocations in each livepatch relocation section refer
to their respective symbols with their symbol indices, and the original
symbol indices (and thus the symtab ordering) must be preserved in order
for apply_relocate_add() to find the right symbol.

Signed-off-by: Jessica Yu <jeyu@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/linux/module.h b/include/linux/module.h
index 2bb0c3085706..3daf2b3a09d2 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -330,6 +330,15 @@ struct mod_kallsyms {
 	char *strtab;
 };
 
+#ifdef CONFIG_LIVEPATCH
+struct klp_modinfo {
+	Elf_Ehdr hdr;
+	Elf_Shdr *sechdrs;
+	char *secstrings;
+	unsigned int symndx;
+};
+#endif
+
 struct module {
 	enum module_state state;
 
@@ -456,7 +465,11 @@ struct module {
 #endif
 
 #ifdef CONFIG_LIVEPATCH
+	bool klp; /* Is this a livepatch module? */
 	bool klp_alive;
+
+	/* Elf information */
+	struct klp_modinfo *klp_info;
 #endif
 
 #ifdef CONFIG_MODULE_UNLOAD
@@ -630,6 +643,18 @@ static inline bool module_requested_async_probing(struct module *module)
 	return module && module->async_probe_requested;
 }
 
+#ifdef CONFIG_LIVEPATCH
+static inline bool is_livepatch_module(struct module *mod)
+{
+	return mod->klp;
+}
+#else /* !CONFIG_LIVEPATCH */
+static inline bool is_livepatch_module(struct module *mod)
+{
+	return false;
+}
+#endif /* CONFIG_LIVEPATCH */
+
 #else /* !CONFIG_MODULES... */
 
 /* Given an address, look for it in the exception tables. */