mirror of https://github.com/dynup/kpatch
kmod/core: support for patching of future loaded modules
This allows a patch module to contain patched functions for modules which haven't been loaded yet. If/when the module is loaded later, it will be patched from the module notifier function.
This commit is contained in:
Josh Poimboeuf
parent
052806fe43
commit
844af68115
175
kmod/core/core.c
175
kmod/core/core.c
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@ -201,6 +201,11 @@ static void kpatch_backtrace_address_verify(void *data, unsigned long address,
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struct kpatch_func *active_func;
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func = &kpmod->funcs[i];
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/* check if patch depends on a future module load */
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if (!func->old_addr)
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continue;
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active_func = kpatch_get_func(func->old_addr);
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if (!active_func) {
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/* patching an unpatched func */
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@ -289,8 +294,9 @@ static int kpatch_apply_patch(void *data)
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/* tentatively add the new funcs to the global func hash */
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for (i = 0; i < num_funcs; i++)
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hash_add_rcu(kpatch_func_hash, &funcs[i].node,
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funcs[i].old_addr);
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if (funcs[i].old_addr)
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hash_add_rcu(kpatch_func_hash, &funcs[i].node,
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funcs[i].old_addr);
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/* memory barrier between func hash add and state change */
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smp_wmb();
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@ -305,7 +311,8 @@ static int kpatch_apply_patch(void *data)
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/* Failed, we have to rollback patching process */
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for (i = 0; i < num_funcs; i++)
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hash_del_rcu(&funcs[i].node);
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if (funcs[i].old_addr)
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hash_del_rcu(&funcs[i].node);
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return -EBUSY;
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}
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@ -334,7 +341,8 @@ static int kpatch_remove_patch(void *data)
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/* Succeeded, remove all updating funcs from hash table */
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for (i = 0; i < num_funcs; i++)
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hash_del_rcu(&funcs[i].node);
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if (funcs[i].old_addr)
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hash_del_rcu(&funcs[i].node);
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return 0;
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}
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@ -522,7 +530,7 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod)
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unsigned long core = (unsigned long)kpmod->mod->module_core;
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unsigned long core_ro_size = kpmod->mod->core_ro_size;
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unsigned long core_size = kpmod->mod->core_size;
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unsigned long src_addr;
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unsigned long src;
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struct module *mod;
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for (i = 0; i < kpmod->dynrelas_nr; i++) {
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@ -530,49 +538,60 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod)
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if (!strcmp(dynrela->objname, "vmlinux")) {
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/* vmlinux */
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ret = kpatch_verify_symbol_match(dynrela->name, dynrela->src);
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/* check if reloc has already been written */
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if (kpmod->enabled)
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continue;
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ret = kpatch_verify_symbol_match(dynrela->name,
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dynrela->src);
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if (ret)
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return ret;
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src_addr = dynrela->src;
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} else {
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/* module, dynrela->src is not right */
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/* module, dynrela->src needs to be discovered */
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/* check if reloc has already been written */
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if (dynrela->src)
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continue;
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/* check if dynrela depends on a future loaded module */
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mutex_lock(&module_mutex);
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mod = find_module(dynrela->objname);
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mutex_unlock(&module_mutex);
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if (!mod) {
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pr_err("unable to find module '%s'\n",
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dynrela->objname);
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return -EINVAL;
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}
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src_addr = kpatch_find_module_symbol(mod, dynrela->name);
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if (!src_addr) {
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if (!mod)
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continue;
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src = kpatch_find_module_symbol(mod, dynrela->name);
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if (!src) {
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pr_err("unable to find symbol '%s' in module '%s'\n",
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dynrela->name, mod->name);
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return -EINVAL;
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}
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dynrela->src = src;
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}
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switch (dynrela->type) {
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case R_X86_64_PC32:
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loc = dynrela->dest;
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val = (u32)(src_addr + dynrela->addend -
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val = (u32)(dynrela->src + dynrela->addend -
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dynrela->dest);
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size = 4;
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break;
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case R_X86_64_32S:
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loc = dynrela->dest;
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val = (s32)src_addr + dynrela->addend;
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val = (s32)dynrela->src + dynrela->addend;
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size = 4;
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break;
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case R_X86_64_64:
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loc = dynrela->dest;
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val = src_addr;
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val = dynrela->src;
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size = 8;
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break;
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default:
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printk("unsupported rela type %ld for source %s (0x%lx <- 0x%lx) at index %d\n",
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dynrela->type, dynrela->name,
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dynrela->dest, src_addr, i);
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dynrela->dest, dynrela->src, i);
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return -EINVAL;
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}
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@ -604,21 +623,24 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod)
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return 0;
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}
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static int kpatch_calculate_old_addr(struct kpatch_func *func)
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static void kpatch_calculate_old_addr(struct kpatch_func *func)
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{
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struct module *module;
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if (!strcmp(func->patch->objname, "vmlinux")) {
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func->old_addr = func->patch->old_offset;
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return 0;
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return;
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}
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/*
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* If the module hasn't been loaded yet, we'll patch it later in
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* kpatch_module_notify().
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*/
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mutex_lock(&module_mutex);
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module = find_module(func->patch->objname);
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if (!module) {
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mutex_unlock(&module_mutex);
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pr_err("patch contains code for a module that is not loaded\n");
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return -EINVAL;
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return;
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}
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/* should never fail because we have the mutex */
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@ -628,6 +650,69 @@ static int kpatch_calculate_old_addr(struct kpatch_func *func)
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func->mod = module;
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func->old_addr = (unsigned long)module->module_core +
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func->patch->old_offset;
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}
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static int kpatch_module_notify(struct notifier_block *nb, unsigned long action,
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void *data)
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{
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struct module *mod = data;
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struct kpatch_module *kpmod;
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int printed = 0, ret = 0, i;
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if (action != MODULE_STATE_COMING)
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return ret;
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down(&kpatch_mutex);
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list_for_each_entry(kpmod, &kpmod_list, list) {
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if (!kpmod->pending)
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continue;
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/* temporarily clear pending, can be set again below */
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kpmod->pending = 0;
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for (i = 0; i < kpmod->patches_nr; i++) {
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struct kpatch_func *func = &kpmod->funcs[i];
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/* check if it has already been patched */
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if (func->old_addr)
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continue;
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/* calculate actual old location (refs if module) */
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kpatch_calculate_old_addr(func);
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if (!func->old_addr) {
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kpmod->pending = 1;
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continue;
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}
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if (!printed) {
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pr_notice("patching newly loaded module '%s'\n",
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mod->name);
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printed = 1;
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}
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ret = kpatch_ftrace_add_func(func->old_addr);
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if (ret)
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goto out;
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/* add to the global func hash */
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hash_add_rcu(kpatch_func_hash, &func->node,
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func->old_addr);
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}
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/* write any newly valid relocations */
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ret = kpatch_write_relocations(kpmod);
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if (ret)
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goto out;
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}
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out:
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up(&kpatch_mutex);
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/* no way to stop the module load on error */
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WARN(ret, "error (%d) patching newly loaded module '%s'\n", ret,
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mod->name);
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return 0;
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}
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@ -640,16 +725,15 @@ int kpatch_register(struct kpatch_module *kpmod, bool replace)
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if (!kpmod->mod || !kpmod->patches || !num_funcs)
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return -EINVAL;
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kpmod->enabled = false;
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funcs = kzalloc(sizeof(*funcs) * num_funcs, GFP_KERNEL);
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if (!funcs)
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return -ENOMEM;
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kpmod->funcs = funcs;
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down(&kpatch_mutex);
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kpmod->enabled = false;
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kpmod->pending = 0;
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kpmod->funcs = funcs;
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list_add_tail(&kpmod->list, &kpmod_list);
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if (!try_module_get(kpmod->mod)) {
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@ -665,9 +749,13 @@ int kpatch_register(struct kpatch_module *kpmod, bool replace)
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func->patch = &kpmod->patches[i];
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/* calculate actual old location (refs if module) */
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ret = kpatch_calculate_old_addr(func);
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if (ret)
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goto err_rollback;
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kpatch_calculate_old_addr(func);
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/* check if patch depends on a future loaded module */
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if (!func->old_addr) {
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kpmod->pending = 1;
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continue;
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}
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ret = kpatch_verify_symbol_match(func->patch->name,
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func->old_addr);
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@ -819,6 +907,8 @@ int kpatch_unregister(struct kpatch_module *kpmod)
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}
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for (i = 0; i < num_funcs; i++) {
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if (!funcs[i].old_addr)
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continue;
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ret = kpatch_ftrace_remove_func(funcs[i].old_addr);
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if (ret) {
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WARN(1, "can't unregister ftrace for address 0x%lx\n",
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@ -843,23 +933,44 @@ out:
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}
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EXPORT_SYMBOL(kpatch_unregister);
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static struct notifier_block kpatch_module_nb = {
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.notifier_call = kpatch_module_notify,
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.priority = INT_MIN, /* called last */
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};
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static int kpatch_init(void)
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{
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int ret;
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kpatch_root_kobj = kobject_create_and_add("kpatch", kernel_kobj);
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if (!kpatch_root_kobj)
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return -ENOMEM;
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kpatch_patches_kobj = kobject_create_and_add("patches",
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kpatch_root_kobj);
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if (!kpatch_patches_kobj)
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return -ENOMEM;
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if (!kpatch_patches_kobj) {
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ret = -ENOMEM;
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goto err_root_kobj;
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}
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ret = register_module_notifier(&kpatch_module_nb);
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if (ret)
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goto err_patches_kobj;
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return 0;
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err_patches_kobj:
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kobject_put(kpatch_patches_kobj);
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err_root_kobj:
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kobject_put(kpatch_root_kobj);
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return ret;
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}
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static void kpatch_exit(void)
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{
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WARN_ON(kpatch_num_patched != 0);
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WARN_ON(unregister_module_notifier(&kpatch_module_nb));
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kobject_put(kpatch_patches_kobj);
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kobject_put(kpatch_root_kobj);
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}
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@ -58,6 +58,7 @@ struct kpatch_module {
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/* private */
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struct list_head list;
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struct kpatch_func *funcs;
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bool pending;
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};
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extern struct kobject *kpatch_patches_kobj;
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@ -1734,7 +1734,11 @@ void kpatch_create_dynamic_rela_sections(struct kpatch_elf *kelf,
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rela->sym->name, result.value, result.size);
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/* dest filed in by rela entry below */
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dynrelas[index].src = result.value;
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if (!strcmp(objname, "vmlinux"))
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dynrelas[index].src = result.value;
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else
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/* for modules, src is discovered at runtime */
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dynrelas[index].src = 0;
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dynrelas[index].addend = rela->addend;
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dynrelas[index].type = rela->type;
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