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Diffstat (limited to 'samples/livepatch/livepatch-shadow-fix2.c')
| -rw-r--r-- | samples/livepatch/livepatch-shadow-fix2.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/samples/livepatch/livepatch-shadow-fix2.c b/samples/livepatch/livepatch-shadow-fix2.c new file mode 100644 index 000000000000..53c1794bdc5f --- /dev/null +++ b/samples/livepatch/livepatch-shadow-fix2.c @@ -0,0 +1,168 @@ +/* + * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +/* + * livepatch-shadow-fix2.c - Shadow variables, livepatch demo + * + * Purpose + * ------- + * + * Adds functionality to livepatch-shadow-mod's in-flight data + * structures through a shadow variable. The livepatch patches a + * routine that periodically inspects data structures, incrementing a + * per-data-structure counter, creating the counter if needed. + * + * + * Usage + * ----- + * + * This module is not intended to be standalone. See the "Usage" + * section of livepatch-shadow-mod.c. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/livepatch.h> +#include <linux/slab.h> + +/* Shadow variable enums */ +#define SV_LEAK 1 +#define SV_COUNTER 2 + +struct dummy { + struct list_head list; + unsigned long jiffies_expire; +}; + +bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies) +{ + int *shadow_count; + int count; + + /* + * Patch: handle in-flight dummy structures, if they do not + * already have a SV_COUNTER shadow variable, then attach a + * new one. + */ + count = 0; + shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER, + &count, sizeof(count), + GFP_NOWAIT); + if (shadow_count) + *shadow_count += 1; + + return time_after(jiffies, d->jiffies_expire); +} + +void livepatch_fix2_dummy_free(struct dummy *d) +{ + void **shadow_leak, *leak; + int *shadow_count; + + /* Patch: copy the memory leak patch from the fix1 module. */ + shadow_leak = klp_shadow_get(d, SV_LEAK); + if (shadow_leak) { + leak = *shadow_leak; + klp_shadow_free(d, SV_LEAK); + kfree(leak); + pr_info("%s: dummy @ %p, prevented leak @ %p\n", + __func__, d, leak); + } else { + pr_info("%s: dummy @ %p leaked!\n", __func__, d); + } + + /* + * Patch: fetch the SV_COUNTER shadow variable and display + * the final count. Detach the shadow variable. + */ + shadow_count = klp_shadow_get(d, SV_COUNTER); + if (shadow_count) { + pr_info("%s: dummy @ %p, check counter = %d\n", + __func__, d, *shadow_count); + klp_shadow_free(d, SV_COUNTER); + } + + kfree(d); +} + +static struct klp_func funcs[] = { + { + .old_name = "dummy_check", + .new_func = livepatch_fix2_dummy_check, + }, + { + .old_name = "dummy_free", + .new_func = livepatch_fix2_dummy_free, + }, { } +}; + +static struct klp_object objs[] = { + { + .name = "livepatch_shadow_mod", + .funcs = funcs, + }, { } +}; + +static struct klp_patch patch = { + .mod = THIS_MODULE, + .objs = objs, +}; + +static int livepatch_shadow_fix2_init(void) +{ + int ret; + + if (!klp_have_reliable_stack() && !patch.immediate) { + /* + * WARNING: Be very careful when using 'patch.immediate' in + * your patches. It's ok to use it for simple patches like + * this, but for more complex patches which change function + * semantics, locking semantics, or data structures, it may not + * be safe. Use of this option will also prevent removal of + * the patch. + * + * See Documentation/livepatch/livepatch.txt for more details. + */ + patch.immediate = true; + pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n"); + } + + ret = klp_register_patch(&patch); + if (ret) + return ret; + ret = klp_enable_patch(&patch); + if (ret) { + WARN_ON(klp_unregister_patch(&patch)); + return ret; + } + return 0; +} + +static void livepatch_shadow_fix2_exit(void) +{ + /* Cleanup any existing SV_COUNTER shadow variables */ + klp_shadow_free_all(SV_COUNTER); + + WARN_ON(klp_unregister_patch(&patch)); +} + +module_init(livepatch_shadow_fix2_init); +module_exit(livepatch_shadow_fix2_exit); +MODULE_LICENSE("GPL"); +MODULE_INFO(livepatch, "Y"); |