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Date: Mon, 9 Nov 2015 23:45:52 -0500
From: Jessica Yu <jeyu@...hat.com>
To: Rusty Russell <rusty@...tcorp.com.au>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Seth Jennings <sjenning@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Vojtech Pavlik <vojtech@...e.com>,
Miroslav Benes <mbenes@...e.cz>
Cc: linux-api@...r.kernel.org, live-patching@...r.kernel.org,
x86@...nel.org, linux-kernel@...r.kernel.org,
Jessica Yu <jeyu@...hat.com>
Subject: [RFC PATCH 2/5] module: save load_info for livepatch modules
In livepatch modules, preserve section, symbol, string information from
the load_info struct in the module loader. This information is used to
patch modules that are not loaded in memory yet; specifically it is used
to resolve remaining symbols and write relocations when the target
module loads.
Signed-off-by: Jessica Yu <jeyu@...hat.com>
---
include/linux/module.h | 25 +++++++++++++++++++++++++
kernel/livepatch/core.c | 17 +++++++++++++++++
kernel/module.c | 36 ++++++++++++++++++++++--------------
3 files changed, 64 insertions(+), 14 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index 3a19c79..c8680b1 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -36,6 +36,20 @@ struct modversion_info {
char name[MODULE_NAME_LEN];
};
+struct load_info {
+ Elf_Ehdr *hdr;
+ unsigned long len;
+ Elf_Shdr *sechdrs;
+ char *secstrings, *strtab;
+ unsigned long symoffs, stroffs;
+ struct _ddebug *debug;
+ unsigned int num_debug;
+ bool sig_ok;
+ struct {
+ unsigned int sym, str, mod, vers, info, pcpu;
+ } index;
+};
+
struct module;
struct module_kobject {
@@ -462,6 +476,8 @@ struct module {
#ifdef CONFIG_LIVEPATCH
bool klp_alive;
+ /* save info to patch to-be-loaded modules */
+ struct load_info *info;
#endif
#ifdef CONFIG_MODULE_UNLOAD
@@ -635,6 +651,15 @@ static inline bool module_requested_async_probing(struct module *module)
return module && module->async_probe_requested;
}
+#ifdef CONFIG_LIVEPATCH
+extern void klp_prepare_patch_module(struct module *mod,
+ struct load_info *info);
+extern int
+apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
+ unsigned int symindex, unsigned int relsec,
+ struct module *me);
+#endif
+
#else /* !CONFIG_MODULES... */
/* Given an address, look for it in the exception tables. */
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 6e53441..087a8c7 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -1001,6 +1001,23 @@ static struct notifier_block klp_module_nb = {
.priority = INT_MIN+1, /* called late but before ftrace notifier */
};
+/*
+ * Save necessary information from info in order to be able to
+ * patch modules that might be loaded later
+ */
+void klp_prepare_patch_module(struct module *mod, struct load_info *info)
+{
+ Elf_Shdr *symsect;
+
+ symsect = info->sechdrs + info->index.sym;
+ /* update sh_addr to point to symtab */
+ symsect->sh_addr = (unsigned long)info->hdr + symsect->sh_offset;
+
+ mod->info = kzalloc(sizeof(*info), GFP_KERNEL);
+ memcpy(mod->info, info, sizeof(*info));
+
+}
+
static int __init klp_init(void)
{
int ret;
diff --git a/kernel/module.c b/kernel/module.c
index 8f051a1..8ae3ca5 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -318,20 +318,6 @@ int unregister_module_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL(unregister_module_notifier);
-struct load_info {
- Elf_Ehdr *hdr;
- unsigned long len;
- Elf_Shdr *sechdrs;
- char *secstrings, *strtab;
- unsigned long symoffs, stroffs;
- struct _ddebug *debug;
- unsigned int num_debug;
- bool sig_ok;
- struct {
- unsigned int sym, str, mod, vers, info, pcpu;
- } index;
-};
-
/* We require a truly strong try_module_get(): 0 means failure due to
ongoing or failed initialization etc. */
static inline int strong_try_module_get(struct module *mod)
@@ -2137,6 +2123,11 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
(long)sym[i].st_value);
break;
+#ifdef CONFIG_LIVEPATCH
+ case SHN_LIVEPATCH:
+ break;
+#endif
+
case SHN_UNDEF:
ksym = resolve_symbol_wait(mod, info, name);
/* Ok if resolved. */
@@ -2185,6 +2176,11 @@ static int apply_relocations(struct module *mod, const struct load_info *info)
if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC))
continue;
+#ifdef CONFIG_LIVEPATCH
+ if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH)
+ continue;
+#endif
+
if (info->sechdrs[i].sh_type == SHT_REL)
err = apply_relocate(info->sechdrs, info->strtab,
info->index.sym, i, mod);
@@ -3530,8 +3526,20 @@ static int load_module(struct load_info *info, const char __user *uargs,
if (err < 0)
goto bug_cleanup;
+#ifdef CONFIG_LIVEPATCH
+ /*
+ * Save sechdrs, indices, and other data from info
+ * in order to patch to-be-loaded modules.
+ * Do not call free_copy() for livepatch modules.
+ */
+ if (get_modinfo((struct load_info *)info, "livepatch"))
+ klp_prepare_patch_module(mod, info);
+ else
+ free_copy(info);
+#else
/* Get rid of temporary copy. */
free_copy(info);
+#endif
/* Done! */
trace_module_load(mod);
--
2.4.3
--
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