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-rw-r--r--Documentation/ABI/testing/sysfs-kernel-livepatch44
-rw-r--r--Documentation/oops-tracing.txt2
-rw-r--r--Documentation/sysctl/kernel.txt1
-rw-r--r--MAINTAINERS15
-rw-r--r--arch/x86/Kconfig3
-rw-r--r--arch/x86/include/asm/livepatch.h46
-rw-r--r--arch/x86/kernel/Makefile1
-rw-r--r--arch/x86/kernel/livepatch.c90
-rw-r--r--include/linux/kernel.h1
-rw-r--r--include/linux/livepatch.h133
-rw-r--r--kernel/Makefile1
-rw-r--r--kernel/livepatch/Kconfig18
-rw-r--r--kernel/livepatch/Makefile3
-rw-r--r--kernel/livepatch/core.c1015
-rw-r--r--kernel/panic.c2
-rw-r--r--samples/Kconfig7
-rw-r--r--samples/Makefile2
-rw-r--r--samples/livepatch/Makefile1
-rw-r--r--samples/livepatch/livepatch-sample.c91
19 files changed, 1475 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch
new file mode 100644
index 000000000000..5bf42a840b22
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-livepatch
@@ -0,0 +1,44 @@
+What: /sys/kernel/livepatch
+Date: Nov 2014
+KernelVersion: 3.19.0
+Contact: live-patching@vger.kernel.org
+Description:
+ Interface for kernel live patching
+
+ The /sys/kernel/livepatch directory contains subdirectories for
+ each loaded live patch module.
+
+What: /sys/kernel/livepatch/<patch>
+Date: Nov 2014
+KernelVersion: 3.19.0
+Contact: live-patching@vger.kernel.org
+Description:
+ The patch directory contains subdirectories for each kernel
+ object (vmlinux or a module) in which it patched functions.
+
+What: /sys/kernel/livepatch/<patch>/enabled
+Date: Nov 2014
+KernelVersion: 3.19.0
+Contact: live-patching@vger.kernel.org
+Description:
+ A writable attribute that indicates whether the patched
+ code is currently applied. Writing 0 will disable the patch
+ while writing 1 will re-enable the patch.
+
+What: /sys/kernel/livepatch/<patch>/<object>
+Date: Nov 2014
+KernelVersion: 3.19.0
+Contact: live-patching@vger.kernel.org
+Description:
+ The object directory contains subdirectories for each function
+ that is patched within the object.
+
+What: /sys/kernel/livepatch/<patch>/<object>/<function>
+Date: Nov 2014
+KernelVersion: 3.19.0
+Contact: live-patching@vger.kernel.org
+Description:
+ The function directory contains attributes regarding the
+ properties and state of the patched function.
+
+ There are currently no such attributes.
diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
index beefb9f82902..f3ac05cc23e4 100644
--- a/Documentation/oops-tracing.txt
+++ b/Documentation/oops-tracing.txt
@@ -270,6 +270,8 @@ characters, each representing a particular tainted value.
15: 'L' if a soft lockup has previously occurred on the system.
+ 16: 'K' if the kernel has been live patched.
+
The primary reason for the 'Tainted: ' string is to tell kernel
debuggers if this is a clean kernel or if anything unusual has
occurred. Tainting is permanent: even if an offending module is
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 75511efefc64..83ab25660fc9 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -843,6 +843,7 @@ can be ORed together:
8192 - An unsigned module has been loaded in a kernel supporting module
signature.
16384 - A soft lockup has previously occurred on the system.
+32768 - The kernel has been live patched.
==============================================================
diff --git a/MAINTAINERS b/MAINTAINERS
index 54c7ce00d85f..71b6c4308119 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5853,6 +5853,21 @@ F: Documentation/misc-devices/lis3lv02d
F: drivers/misc/lis3lv02d/
F: drivers/platform/x86/hp_accel.c
+LIVE PATCHING
+M: Josh Poimboeuf <jpoimboe@redhat.com>
+M: Seth Jennings <sjenning@redhat.com>
+M: Jiri Kosina <jkosina@suse.cz>
+M: Vojtech Pavlik <vojtech@suse.cz>
+S: Maintained
+F: kernel/livepatch/
+F: include/linux/livepatch.h
+F: arch/x86/include/asm/livepatch.h
+F: arch/x86/kernel/livepatch.c
+F: Documentation/ABI/testing/sysfs-kernel-livepatch
+F: samples/livepatch/
+L: live-patching@vger.kernel.org
+T: git git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching.git
+
LLC (802.2)
M: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
S: Maintained
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 019f4e5c2b75..33ce9a344e38 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -17,6 +17,7 @@ config X86_64
depends on 64BIT
select X86_DEV_DMA_OPS
select ARCH_USE_CMPXCHG_LOCKREF
+ select HAVE_LIVEPATCH
### Arch settings
config X86
@@ -2028,6 +2029,8 @@ config CMDLINE_OVERRIDE
This is used to work around broken boot loaders. This should
be set to 'N' under normal conditions.
+source "kernel/livepatch/Kconfig"
+
endmenu
config ARCH_ENABLE_MEMORY_HOTPLUG
diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h
new file mode 100644
index 000000000000..a455a53d789a
--- /dev/null
+++ b/arch/x86/include/asm/livepatch.h
@@ -0,0 +1,46 @@
+/*
+ * livepatch.h - x86-specific Kernel Live Patching Core
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ * Copyright (C) 2014 SUSE
+ *
+ * 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/>.
+ */
+
+#ifndef _ASM_X86_LIVEPATCH_H
+#define _ASM_X86_LIVEPATCH_H
+
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#ifdef CONFIG_LIVEPATCH
+static inline int klp_check_compiler_support(void)
+{
+#ifndef CC_USING_FENTRY
+ return 1;
+#endif
+ return 0;
+}
+extern int klp_write_module_reloc(struct module *mod, unsigned long type,
+ unsigned long loc, unsigned long value);
+
+static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
+{
+ regs->ip = ip;
+}
+#else
+#error Live patching support is disabled; check CONFIG_LIVEPATCH
+#endif
+
+#endif /* _ASM_X86_LIVEPATCH_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 5d4502c8b983..732223496968 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o
obj-y += apic/
obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
+obj-$(CONFIG_LIVEPATCH) += livepatch.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
obj-$(CONFIG_X86_TSC) += trace_clock.o
diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
new file mode 100644
index 000000000000..ff3c3101d003
--- /dev/null
+++ b/arch/x86/kernel/livepatch.c
@@ -0,0 +1,90 @@
+/*
+ * livepatch.c - x86-specific Kernel Live Patching Core
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ * Copyright (C) 2014 SUSE
+ *
+ * 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/>.
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+#include <asm/page_types.h>
+#include <asm/elf.h>
+#include <asm/livepatch.h>
+
+/**
+ * klp_write_module_reloc() - write a relocation in a module
+ * @mod: module in which the section to be modified is found
+ * @type: ELF relocation type (see asm/elf.h)
+ * @loc: address that the relocation should be written to
+ * @value: relocation value (sym address + addend)
+ *
+ * This function writes a relocation to the specified location for
+ * a particular module.
+ */
+int klp_write_module_reloc(struct module *mod, unsigned long type,
+ unsigned long loc, unsigned long value)
+{
+ int ret, numpages, size = 4;
+ bool readonly;
+ unsigned long val;
+ unsigned long core = (unsigned long)mod->module_core;
+ unsigned long core_ro_size = mod->core_ro_size;
+ unsigned long core_size = mod->core_size;
+
+ switch (type) {
+ case R_X86_64_NONE:
+ return 0;
+ case R_X86_64_64:
+ val = value;
+ size = 8;
+ break;
+ case R_X86_64_32:
+ val = (u32)value;
+ break;
+ case R_X86_64_32S:
+ val = (s32)value;
+ break;
+ case R_X86_64_PC32:
+ val = (u32)(value - loc);
+ break;
+ default:
+ /* unsupported relocation type */
+ return -EINVAL;
+ }
+
+ if (loc < core || loc >= core + core_size)
+ /* loc does not point to any symbol inside the module */
+ return -EINVAL;
+
+ if (loc < core + core_ro_size)
+ readonly = true;
+ else
+ readonly = false;
+
+ /* determine if the relocation spans a page boundary */
+ numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
+
+ if (readonly)
+ set_memory_rw(loc & PAGE_MASK, numpages);
+
+ ret = probe_kernel_write((void *)loc, &val, size);
+
+ if (readonly)
+ set_memory_ro(loc & PAGE_MASK, numpages);
+
+ return ret;
+}
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 64ce58bee6f5..e42e7dc34c68 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -471,6 +471,7 @@ extern enum system_states {
#define TAINT_OOT_MODULE 12
#define TAINT_UNSIGNED_MODULE 13
#define TAINT_SOFTLOCKUP 14
+#define TAINT_LIVEPATCH 15
extern const char hex_asc[];
#define hex_asc_lo(x) hex_asc[((x) & 0x0f)]
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
new file mode 100644
index 000000000000..95023fd8b00d
--- /dev/null
+++ b/include/linux/livepatch.h
@@ -0,0 +1,133 @@
+/*
+ * livepatch.h - Kernel Live Patching Core
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ * Copyright (C) 2014 SUSE
+ *
+ * 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/>.
+ */
+
+#ifndef _LINUX_LIVEPATCH_H_
+#define _LINUX_LIVEPATCH_H_
+
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#if IS_ENABLED(CONFIG_LIVEPATCH)
+
+#include <asm/livepatch.h>
+
+enum klp_state {
+ KLP_DISABLED,
+ KLP_ENABLED
+};
+
+/**
+ * struct klp_func - function structure for live patching
+ * @old_name: name of the function to be patched
+ * @new_func: pointer to the patched function code
+ * @old_addr: a hint conveying at what address the old function
+ * can be found (optional, vmlinux patches only)
+ * @kobj: kobject for sysfs resources
+ * @state: tracks function-level patch application state
+ * @stack_node: list node for klp_ops func_stack list
+ */
+struct klp_func {
+ /* external */
+ const char *old_name;
+ void *new_func;
+ /*
+ * The old_addr field is optional and can be used to resolve
+ * duplicate symbol names in the vmlinux object. If this
+ * information is not present, the symbol is located by name
+ * with kallsyms. If the name is not unique and old_addr is
+ * not provided, the patch application fails as there is no
+ * way to resolve the ambiguity.
+ */
+ unsigned long old_addr;
+
+ /* internal */
+ struct kobject kobj;
+ enum klp_state state;
+ struct list_head stack_node;
+};
+
+/**
+ * struct klp_reloc - relocation structure for live patching
+ * @loc: address where the relocation will be written
+ * @val: address of the referenced symbol (optional,
+ * vmlinux patches only)
+ * @type: ELF relocation type
+ * @name: name of the referenced symbol (for lookup/verification)
+ * @addend: offset from the referenced symbol
+ * @external: symbol is either exported or within the live patch module itself
+ */
+struct klp_reloc {
+ unsigned long loc;
+ unsigned long val;
+ unsigned long type;
+ const char *name;
+ int addend;
+ int external;
+};
+
+/**
+ * struct klp_object - kernel object structure for live patching
+ * @name: module name (or NULL for vmlinux)
+ * @relocs: relocation entries to be applied at load time
+ * @funcs: function entries for functions to be patched in the object
+ * @kobj: kobject for sysfs resources
+ * @mod: kernel module associated with the patched object
+ * (NULL for vmlinux)
+ * @state: tracks object-level patch application state
+ */
+struct klp_object {
+ /* external */
+ const char *name;
+ struct klp_reloc *relocs;
+ struct klp_func *funcs;
+
+ /* internal */
+ struct kobject *kobj;
+ struct module *mod;
+ enum klp_state state;
+};
+
+/**
+ * struct klp_patch - patch structure for live patching
+ * @mod: reference to the live patch module
+ * @objs: object entries for kernel objects to be patched
+ * @list: list node for global list of registered patches
+ * @kobj: kobject for sysfs resources
+ * @state: tracks patch-level application state
+ */
+struct klp_patch {
+ /* external */
+ struct module *mod;
+ struct klp_object *objs;
+
+ /* internal */
+ struct list_head list;
+ struct kobject kobj;
+ enum klp_state state;
+};
+
+extern int klp_register_patch(struct klp_patch *);
+extern int klp_unregister_patch(struct klp_patch *);
+extern int klp_enable_patch(struct klp_patch *);
+extern int klp_disable_patch(struct klp_patch *);
+
+#endif /* CONFIG_LIVEPATCH */
+
+#endif /* _LINUX_LIVEPATCH_H_ */
diff --git a/kernel/Makefile b/kernel/Makefile
index a59481a3fa6c..616994f0a76f 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -26,6 +26,7 @@ obj-y += power/
obj-y += printk/
obj-y += irq/
obj-y += rcu/
+obj-y += livepatch/
obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
obj-$(CONFIG_FREEZER) += freezer.o
diff --git a/kernel/livepatch/Kconfig b/kernel/livepatch/Kconfig
new file mode 100644
index 000000000000..045022557936
--- /dev/null
+++ b/kernel/livepatch/Kconfig
@@ -0,0 +1,18 @@
+config HAVE_LIVEPATCH
+ bool
+ help
+ Arch supports kernel live patching
+
+config LIVEPATCH
+ bool "Kernel Live Patching"
+ depends on DYNAMIC_FTRACE_WITH_REGS
+ depends on MODULES
+ depends on SYSFS
+ depends on KALLSYMS_ALL
+ depends on HAVE_LIVEPATCH
+ help
+ Say Y here if you want to support kernel live patching.
+ This option has no runtime impact until a kernel "patch"
+ module uses the interface provided by this option to register
+ a patch, causing calls to patched functions to be redirected
+ to new function code contained in the patch module.
diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile
new file mode 100644
index 000000000000..e8780c0901d9
--- /dev/null
+++ b/kernel/livepatch/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_LIVEPATCH) += livepatch.o
+
+livepatch-objs := core.o
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
new file mode 100644
index 000000000000..ff7f47d026ac
--- /dev/null
+++ b/kernel/livepatch/core.c
@@ -0,0 +1,1015 @@
+/*
+ * core.c - Kernel Live Patching Core
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ * Copyright (C) 2014 SUSE
+ *
+ * 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/>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/ftrace.h>
+#include <linux/list.h>
+#include <linux/kallsyms.h>
+#include <linux/livepatch.h>
+
+/**
+ * struct klp_ops - structure for tracking registered ftrace ops structs
+ *
+ * A single ftrace_ops is shared between all enabled replacement functions
+ * (klp_func structs) which have the same old_addr. This allows the switch
+ * between function versions to happen instantaneously by updating the klp_ops
+ * struct's func_stack list. The winner is the klp_func at the top of the
+ * func_stack (front of the list).
+ *
+ * @node: node for the global klp_ops list
+ * @func_stack: list head for the stack of klp_func's (active func is on top)
+ * @fops: registered ftrace ops struct
+ */
+struct klp_ops {
+ struct list_head node;
+ struct list_head func_stack;
+ struct ftrace_ops fops;
+};
+
+/*
+ * The klp_mutex protects the global lists and state transitions of any
+ * structure reachable from them. References to any structure must be obtained
+ * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
+ * ensure it gets consistent data).
+ */
+static DEFINE_MUTEX(klp_mutex);
+
+static LIST_HEAD(klp_patches);
+static LIST_HEAD(klp_ops);
+
+static struct kobject *klp_root_kobj;
+
+static struct klp_ops *klp_find_ops(unsigned long old_addr)
+{
+ struct klp_ops *ops;
+ struct klp_func *func;
+
+ list_for_each_entry(ops, &klp_ops, node) {
+ func = list_first_entry(&ops->func_stack, struct klp_func,
+ stack_node);
+ if (func->old_addr == old_addr)
+ return ops;
+ }
+
+ return NULL;
+}
+
+static bool klp_is_module(struct klp_object *obj)
+{
+ return obj->name;
+}
+
+static bool klp_is_object_loaded(struct klp_object *obj)
+{
+ return !obj->name || obj->mod;
+}
+
+/* sets obj->mod if object is not vmlinux and module is found */
+static void klp_find_object_module(struct klp_object *obj)
+{
+ if (!klp_is_module(obj))
+ return;
+
+ mutex_lock(&module_mutex);
+ /*
+ * We don't need to take a reference on the module here because we have
+ * the klp_mutex, which is also taken by the module notifier. This
+ * prevents any module from unloading until we release the klp_mutex.
+ */
+ obj->mod = find_module(obj->name);
+ mutex_unlock(&module_mutex);
+}
+
+/* klp_mutex must be held by caller */
+static bool klp_is_patch_registered(struct klp_patch *patch)
+{
+ struct klp_patch *mypatch;
+
+ list_for_each_entry(mypatch, &klp_patches, list)
+ if (mypatch == patch)
+ return true;
+
+ return false;
+}
+
+static bool klp_initialized(void)
+{
+ return klp_root_kobj;
+}
+
+struct klp_find_arg {
+ const char *objname;
+ const char *name;
+ unsigned long addr;
+ /*
+ * If count == 0, the symbol was not found. If count == 1, a unique
+ * match was found and addr is set. If count > 1, there is
+ * unresolvable ambiguity among "count" number of symbols with the same
+ * name in the same object.
+ */
+ unsigned long count;
+};
+
+static int klp_find_callback(void *data, const char *name,
+ struct module *mod, unsigned long addr)
+{
+ struct klp_find_arg *args = data;
+
+ if ((mod && !args->objname) || (!mod && args->objname))
+ return 0;
+
+ if (strcmp(args->name, name))
+ return 0;
+
+ if (args->objname && strcmp(args->objname, mod->name))
+ return 0;
+
+ /*
+ * args->addr might be overwritten if another match is found
+ * but klp_find_object_symbol() handles this and only returns the
+ * addr if count == 1.
+ */
+ args->addr = addr;
+ args->count++;
+
+ return 0;
+}
+
+static int klp_find_object_symbol(const char *objname, const char *name,
+ unsigned long *addr)
+{
+ struct klp_find_arg args = {
+ .objname = objname,
+ .name = name,
+ .addr = 0,
+ .count = 0
+ };
+
+ kallsyms_on_each_symbol(klp_find_callback, &args);
+
+ if (args.count == 0)
+ pr_err("symbol '%s' not found in symbol table\n", name);
+ else if (args.count > 1)
+ pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n",
+ args.count, name, objname);
+ else {
+ *addr = args.addr;
+ return 0;
+ }
+
+ *addr = 0;
+ return -EINVAL;
+}
+
+struct klp_verify_args {
+ const char *name;
+ const unsigned long addr;
+};
+
+static int klp_verify_callback(void *data, const char *name,
+ struct module *mod, unsigned long addr)
+{
+ struct klp_verify_args *args = data;
+
+ if (!mod &&
+ !strcmp(args->name, name) &&
+ args->addr == addr)
+ return 1;
+
+ return 0;
+}
+
+static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
+{
+ struct klp_verify_args args = {
+ .name = name,
+ .addr = addr,
+ };
+
+ if (kallsyms_on_each_symbol(klp_verify_callback, &args))
+ return 0;
+
+ pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
+ name, addr);
+ return -EINVAL;
+}
+
+static int klp_find_verify_func_addr(struct klp_object *obj,
+ struct klp_func *func)
+{
+ int ret;
+
+#if defined(CONFIG_RANDOMIZE_BASE)
+ /* KASLR is enabled, disregard old_addr from user */
+ func->old_addr = 0;
+#endif
+
+ if (!func->old_addr || klp_is_module(obj))
+ ret = klp_find_object_symbol(obj->name, func->old_name,
+ &func->old_addr);
+ else
+ ret = klp_verify_vmlinux_symbol(func->old_name,
+ func->old_addr);
+
+ return ret;
+}
+
+/*
+ * external symbols are located outside the parent object (where the parent
+ * object is either vmlinux or the kmod being patched).
+ */
+static int klp_find_external_symbol(struct module *pmod, const char *name,
+ unsigned long *addr)
+{
+ const struct kernel_symbol *sym;
+
+ /* first, check if it's an exported symbol */
+ preempt_disable();
+ sym = find_symbol(name, NULL, NULL, true, true);
+ preempt_enable();
+ if (sym) {
+ *addr = sym->value;
+ return 0;
+ }
+
+ /* otherwise check if it's in another .o within the patch module */
+ return klp_find_object_symbol(pmod->name, name, addr);
+}
+
+static int klp_write_object_relocations(struct module *pmod,
+ struct klp_object *obj)
+{
+ int ret;
+ struct klp_reloc *reloc;
+
+ if (WARN_ON(!klp_is_object_loaded(obj)))
+ return -EINVAL;
+
+ if (WARN_ON(!obj->relocs))
+ return -EINVAL;
+
+ for (reloc = obj->relocs; reloc->name; reloc++) {
+ if (!klp_is_module(obj)) {
+ ret = klp_verify_vmlinux_symbol(reloc->name,
+ reloc->val);
+ if (ret)
+ return ret;
+ } else {
+ /* module, reloc->val needs to be discovered */
+ if (reloc->external)
+ ret = klp_find_external_symbol(pmod,
+ reloc->name,
+ &reloc->val);
+ else
+ ret = klp_find_object_symbol(obj->mod->name,
+ reloc->name,
+ &reloc->val);
+ if (ret)
+ return ret;
+ }
+ ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
+ reloc->val + reloc->addend);
+ if (ret) {
+ pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
+ reloc->name, reloc->val, ret);
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static void notrace klp_ftrace_handler(unsigned long ip,
+ unsigned long parent_ip,
+ struct ftrace_ops *fops,
+ struct pt_regs *regs)
+{
+ struct klp_ops *ops;
+ struct klp_func *func;
+
+ ops = container_of(fops, struct klp_ops, fops);
+
+ rcu_read_lock();
+ func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
+ stack_node);
+ rcu_read_unlock();
+
+ if (WARN_ON_ONCE(!func))
+ return;
+
+ klp_arch_set_pc(regs, (unsigned long)func->new_func);
+}
+
+static int klp_disable_func(struct klp_func *func)
+{
+ struct klp_ops *ops;
+ int ret;
+
+ if (WARN_ON(func->state != KLP_ENABLED))
+ return -EINVAL;
+
+ if (WARN_ON(!func->old_addr))
+ return -EINVAL;
+
+ ops = klp_find_ops(func->old_addr);
+ if (WARN_ON(!ops))
+ return -EINVAL;
+
+ if (list_is_singular(&ops->func_stack)) {
+ ret = unregister_ftrace_function(&ops->fops);
+ if (ret) {
+ pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
+ func->old_name, ret);
+ return ret;
+ }
+
+ ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
+ if (ret)
+ pr_warn("function unregister succeeded but failed to clear the filter\n");
+
+ list_del_rcu(&func->stack_node);
+ list_del(&ops->node);
+ kfree(ops);
+ } else {
+ list_del_rcu(&func->stack_node);
+ }
+
+ func->state = KLP_DISABLED;
+
+ return 0;
+}
+
+static int klp_enable_func(struct klp_func *func)
+{
+ struct klp_ops *ops;
+ int ret;
+
+ if (WARN_ON(!func->old_addr))
+ return -EINVAL;
+
+ if (WARN_ON(func->state != KLP_DISABLED))
+ return -EINVAL;
+
+ ops = klp_find_ops(func->old_addr);
+ if (!ops) {
+ ops = kzalloc(sizeof(*ops), GFP_KERNEL);
+ if (!ops)
+ return -ENOMEM;
+
+ ops->fops.func = klp_ftrace_handler;
+ ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
+ FTRACE_OPS_FL_DYNAMIC |
+ FTRACE_OPS_FL_IPMODIFY;
+
+ list_add(&ops->node, &klp_ops);
+
+ INIT_LIST_HEAD(&ops->func_stack);
+ list_add_rcu(&func->stack_node, &ops->func_stack);
+
+ ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
+ if (ret) {
+ pr_err("failed to set ftrace filter for function '%s' (%d)\n",
+ func->old_name, ret);
+ goto err;
+ }
+
+ ret = register_ftrace_function(&ops->fops);
+ if (ret) {
+ pr_err("failed to register ftrace handler for function '%s' (%d)\n",
+ func->old_name, ret);
+ ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
+ goto err;
+ }
+
+
+ } else {
+ list_add_rcu(&func->stack_node, &ops->func_stack);
+ }
+
+ func->state = KLP_ENABLED;
+
+ return 0;
+
+err:
+ list_del_rcu(&func->stack_node);
+ list_del(&ops->node);
+ kfree(ops);
+ return ret;
+}
+
+static int klp_disable_object(struct klp_object *obj)
+{
+ struct klp_func *func;
+ int ret;
+
+ for (func = obj->funcs; func->old_name; func++) {
+ if (func->state != KLP_ENABLED)
+ continue;
+
+ ret = klp_disable_func(func);
+ if (ret)
+ return ret;
+ }
+
+ obj->state = KLP_DISABLED;
+
+ return 0;
+}
+
+static int klp_enable_object(struct klp_object *obj)
+{
+ struct klp_func *func;
+ int ret;
+
+ if (WARN_ON(obj->state != KLP_DISABLED))
+ return -EINVAL;
+
+ if (WARN_ON(!klp_is_object_loaded(obj)))
+ return -EINVAL;
+
+ for (func = obj->funcs; func->old_name; func++) {
+ ret = klp_enable_func(func);
+ if (ret)
+ goto unregister;
+ }
+ obj->state = KLP_ENABLED;
+
+ return 0;
+
+unregister:
+ WARN_ON(klp_disable_object(obj));
+ return ret;
+}
+
+static int __klp_disable_patch(struct klp_patch *patch)
+{
+ struct klp_object *obj;
+ int ret;
+
+ /* enforce stacking: only the last enabled patch can be disabled */
+ if (!list_is_last(&patch->list, &klp_patches) &&
+ list_next_entry(patch, list)->state == KLP_ENABLED)
+ return -EBUSY;
+
+ pr_notice("disabling patch '%s'\n", patch->mod->name);
+
+ for (obj = patch->objs; obj->funcs; obj++) {
+ if (obj->state != KLP_ENABLED)
+ continue;
+
+ ret = klp_disable_object(obj);
+ if (ret)
+ return ret;
+ }
+
+ patch->state = KLP_DISABLED;
+
+ return 0;
+}
+
+/**
+ * klp_disable_patch() - disables a registered patch
+ * @patch: The registered, enabled patch to be disabled
+ *
+ * Unregisters the patched functions from ftrace.
+ *
+ * Return: 0 on success, otherwise error
+ */
+int klp_disable_patch(struct klp_patch *patch)
+{
+ int ret;
+
+ mutex_lock(&klp_mutex);
+
+ if (!klp_is_patch_registered(patch)) {
+ ret = -EINVAL;
+ goto err;
+ }
+
+ if (patch->state == KLP_DISABLED) {
+ ret = -EINVAL;
+ goto err;
+ }
+
+ ret = __klp_disable_patch(patch);
+
+err:
+ mutex_unlock(&klp_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(klp_disable_patch);
+
+static int __klp_enable_patch(struct klp_patch *patch)
+{
+ struct klp_object *obj;
+ int ret;
+
+ if (WARN_ON(patch->state != KLP_DISABLED))
+ return -EINVAL;
+
+ /* enforce stacking: only the first disabled patch can be enabled */
+ if (patch->list.prev != &klp_patches &&
+ list_prev_entry(patch, list)->state == KLP_DISABLED)
+ return -EBUSY;
+
+ pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
+ add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
+
+ pr_notice("enabling patch '%s'\n", patch->mod->name);
+
+ for (obj = patch->objs; obj->funcs; obj++) {
+ klp_find_object_module(obj);
+
+ if (!klp_is_object_loaded(obj))
+ continue;
+
+ ret = klp_enable_object(obj);
+ if (ret)
+ goto unregister;
+ }
+
+ patch->state = KLP_ENABLED;
+
+ return 0;
+
+unregister:
+ WARN_ON(__klp_disable_patch(patch));
+ return ret;
+}
+
+/**
+ * klp_enable_patch() - enables a registered patch
+ * @patch: The registered, disabled patch to be enabled
+ *
+ * Performs the needed symbol lookups and code relocations,
+ * then registers the patched functions with ftrace.
+ *
+ * Return: 0 on success, otherwise error
+ */
+int klp_enable_patch(struct klp_patch *patch)
+{
+ int ret;
+
+ mutex_lock(&klp_mutex);
+
+ if (!klp_is_patch_registered(patch)) {
+ ret = -EINVAL;
+ goto err;
+ }
+
+ ret = __klp_enable_patch(patch);
+
+err:
+ mutex_unlock(&klp_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(klp_enable_patch);
+
+/*
+ * Sysfs Interface
+ *
+ * /sys/kernel/livepatch
+ * /sys/kernel/livepatch/<patch>
+ * /sys/kernel/livepatch/<patch>/enabled
+ * /sys/kernel/livepatch/<patch>/<object>
+ * /sys/kernel/livepatch/<patch>/<object>/<func>
+ */
+
+static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct klp_patch *patch;
+ int ret;
+ unsigned long val;
+
+ ret = kstrtoul(buf, 10, &val);
+ if (ret)
+ return -EINVAL;
+
+ if (val != KLP_DISABLED && val != KLP_ENABLED)
+ return -EINVAL;
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+
+ mutex_lock(&klp_mutex);
+
+ if (val == patch->state) {
+ /* already in requested state */
+ ret = -EINVAL;
+ goto err;
+ }
+
+ if (val == KLP_ENABLED) {
+ ret = __klp_enable_patch(patch);
+ if (ret)
+ goto err;
+ } else {
+ ret = __klp_disable_patch(patch);
+ if (ret)
+ goto err;
+ }
+
+ mutex_unlock(&klp_mutex);
+
+ return count;
+
+err:
+ mutex_unlock(&klp_mutex);
+ return ret;
+}
+
+static ssize_t enabled_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct klp_patch *patch;
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
+}
+
+static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
+static struct attribute *klp_patch_attrs[] = {
+ &enabled_kobj_attr.attr,
+ NULL
+};
+
+static void klp_kobj_release_patch(struct kobject *kobj)
+{
+ /*
+ * Once we have a consistency model we'll need to module_put() the
+ * patch module here. See klp_register_patch() for more details.
+ */
+}
+
+static struct kobj_type klp_ktype_patch = {
+ .release = klp_kobj_release_patch,
+ .sysfs_ops = &kobj_sysfs_ops,
+ .default_attrs = klp_patch_attrs,
+};
+
+static void klp_kobj_release_func(struct kobject *kobj)
+{
+}
+
+static struct kobj_type klp_ktype_func = {
+ .release = klp_kobj_release_func,
+ .sysfs_ops = &kobj_sysfs_ops,
+};
+
+/*
+ * Free all functions' kobjects in the array up to some limit. When limit is
+ * NULL, all kobjects are freed.
+ */
+static void klp_free_funcs_limited(struct klp_object *obj,
+ struct klp_func *limit)
+{
+ struct klp_func *func;
+
+ for (func = obj->funcs; func->old_name && func != limit; func++)
+ kobject_put(&func->kobj);
+}
+
+/* Clean up when a patched object is unloaded */
+static void klp_free_object_loaded(struct klp_object *obj)
+{
+ struct klp_func *func;
+
+ obj->mod = NULL;
+
+ for (func = obj->funcs; func->old_name; func++)
+ func->old_addr = 0;
+}
+
+/*
+ * Free all objects' kobjects in the array up to some limit. When limit is
+ * NULL, all kobjects are freed.
+ */
+static void klp_free_objects_limited(struct klp_patch *patch,
+ struct klp_object *limit)
+{
+ struct klp_object *obj;
+
+ for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
+ klp_free_funcs_limited(obj, NULL);
+ kobject_put(obj->kobj);
+ }
+}
+
+static void klp_free_patch(struct klp_patch *patch)
+{
+ klp_free_objects_limited(patch, NULL);
+ if (!list_empty(&patch->list))
+ list_del(&patch->list);
+ kobject_put(&patch->kobj);
+}
+
+static int klp_init_func(struct klp_object *obj, struct klp_func *func)
+{
+ INIT_LIST_HEAD(&func->stack_node);
+ func->state = KLP_DISABLED;
+
+ return kobject_init_and_add(&func->kobj, &klp_ktype_func,
+ obj->kobj, func->old_name);
+}
+
+/* parts of the initialization that is done only when the object is loaded */
+static int klp_init_object_loaded(struct klp_patch *patch,
+ struct klp_object *obj)
+{
+ struct klp_func *func;
+ int ret;
+
+ if (obj->relocs) {
+ ret = klp_write_object_relocations(patch->mod, obj);
+ if (ret)
+ return ret;
+ }
+
+ for (func = obj->funcs; func->old_name; func++) {
+ ret = klp_find_verify_func_addr(obj, func);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
+{
+ struct klp_func *func;
+ int ret;
+ const char *name;
+
+ if (!obj->funcs)
+ return -EINVAL;
+
+ obj->state = KLP_DISABLED;
+
+ klp_find_object_module(obj);
+
+ name = klp_is_module(obj) ? obj->name : "vmlinux";
+ obj->kobj = kobject_create_and_add(name, &patch->kobj);
+ if (!obj->kobj)
+ return -ENOMEM;
+
+ for (func = obj->funcs; func->old_name; func++) {
+ ret = klp_init_func(obj, func);
+ if (ret)
+ goto free;
+ }
+
+ if (klp_is_object_loaded(obj)) {
+ ret = klp_init_object_loaded(patch, obj);
+ if (ret)
+ goto free;
+ }
+
+ return 0;
+
+free:
+ klp_free_funcs_limited(obj, func);
+ kobject_put(obj->kobj);
+ return ret;
+}
+
+static int klp_init_patch(struct klp_patch *patch)
+{
+ struct klp_object *obj;
+ int ret;
+
+ if (!patch->objs)
+ return -EINVAL;
+
+ mutex_lock(&klp_mutex);
+
+ patch->state = KLP_DISABLED;
+
+ ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
+ klp_root_kobj, patch->mod->name);
+ if (ret)
+ goto unlock;
+
+ for (obj = patch->objs; obj->funcs; obj++) {
+ ret = klp_init_object(patch, obj);
+ if (ret)
+ goto free;
+ }
+
+ list_add_tail(&patch->list, &klp_patches);
+
+ mutex_unlock(&klp_mutex);
+
+ return 0;
+
+free:
+ klp_free_objects_limited(patch, obj);
+ kobject_put(&patch->kobj);
+unlock:
+ mutex_unlock(&klp_mutex);
+ return ret;
+}
+
+/**
+ * klp_unregister_patch() - unregisters a patch
+ * @patch: Disabled patch to be unregistered
+ *
+ * Frees the data structures and removes the sysfs interface.
+ *
+ * Return: 0 on success, otherwise error
+ */
+int klp_unregister_patch(struct klp_patch *patch)
+{
+ int ret = 0;
+
+ mutex_lock(&klp_mutex);
+
+ if (!klp_is_patch_registered(patch)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (patch->state == KLP_ENABLED) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ klp_free_patch(patch);
+
+out:
+ mutex_unlock(&klp_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(klp_unregister_patch);
+
+/**
+ * klp_register_patch() - registers a patch
+ * @patch: Patch to be registered
+ *
+ * Initializes the data structure associated with the patch and
+ * creates the sysfs interface.
+ *
+ * Return: 0 on success, otherwise error
+ */
+int klp_register_patch(struct klp_patch *patch)
+{
+ int ret;
+
+ if (!klp_initialized())
+ return -ENODEV;
+
+ if (!patch || !patch->mod)
+ return -EINVAL;
+
+ /*
+ * A reference is taken on the patch module to prevent it from being
+ * unloaded. Right now, we don't allow patch modules to unload since
+ * there is currently no method to determine if a thread is still
+ * running in the patched code contained in the patch module once
+ * the ftrace registration is successful.
+ */
+ if (!try_module_get(patch->mod))
+ return -ENODEV;
+
+ ret = klp_init_patch(patch);
+ if (ret)
+ module_put(patch->mod);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(klp_register_patch);
+
+static void klp_module_notify_coming(struct klp_patch *patch,
+ struct klp_object *obj)
+{
+ struct module *pmod = patch->mod;
+ struct module *mod = obj->mod;
+ int ret;
+
+ ret = klp_init_object_loaded(patch, obj);
+ if (ret)
+ goto err;
+
+ if (patch->state == KLP_DISABLED)
+ return;
+
+ pr_notice("applying patch '%s' to loading module '%s'\n",
+ pmod->name, mod->name);
+
+ ret = klp_enable_object(obj);
+ if (!ret)
+ return;
+
+err:
+ pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
+ pmod->name, mod->name, ret);
+}
+
+static void klp_module_notify_going(struct klp_patch *patch,
+ struct klp_object *obj)
+{
+ struct module *pmod = patch->mod;
+ struct module *mod = obj->mod;
+ int ret;
+
+ if (patch->state == KLP_DISABLED)
+ goto disabled;
+
+ pr_notice("reverting patch '%s' on unloading module '%s'\n",
+ pmod->name, mod->name);
+
+ ret = klp_disable_object(obj);
+ if (ret)
+ pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
+ pmod->name, mod->name, ret);
+
+disabled:
+ klp_free_object_loaded(obj);
+}
+
+static int klp_module_notify(struct notifier_block *nb, unsigned long action,
+ void *data)
+{
+ struct module *mod = data;
+ struct klp_patch *patch;
+ struct klp_object *obj;
+
+ if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
+ return 0;
+
+ mutex_lock(&klp_mutex);
+
+ list_for_each_entry(patch, &klp_patches, list) {
+ for (obj = patch->objs; obj->funcs; obj++) {
+ if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
+ continue;
+
+ if (action == MODULE_STATE_COMING) {
+ obj->mod = mod;
+ klp_module_notify_coming(patch, obj);
+ } else /* MODULE_STATE_GOING */
+ klp_module_notify_going(patch, obj);
+
+ break;
+ }
+ }
+
+ mutex_unlock(&klp_mutex);
+
+ return 0;
+}
+
+static struct notifier_block klp_module_nb = {
+ .notifier_call = klp_module_notify,
+ .priority = INT_MIN+1, /* called late but before ftrace notifier */
+};
+
+static int klp_init(void)
+{
+ int ret;
+
+ ret = klp_check_compiler_support();
+ if (ret) {
+ pr_info("Your compiler is too old; turning off.\n");
+ return -EINVAL;
+ }
+
+ ret = register_module_notifier(&klp_module_nb);
+ if (ret)
+ return ret;
+
+ klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
+ if (!klp_root_kobj) {
+ ret = -ENOMEM;
+ goto unregister;
+ }
+
+ return 0;
+
+unregister:
+ unregister_module_notifier(&klp_module_nb);
+ return ret;
+}
+
+module_init(klp_init);
diff --git a/kernel/panic.c b/kernel/panic.c
index 4d8d6f906dec..8136ad76e5fd 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -226,6 +226,7 @@ static const struct tnt tnts[] = {
{ TAINT_OOT_MODULE, 'O', ' ' },
{ TAINT_UNSIGNED_MODULE, 'E', ' ' },
{ TAINT_SOFTLOCKUP, 'L', ' ' },
+ { TAINT_LIVEPATCH, 'K', ' ' },
};
/**
@@ -246,6 +247,7 @@ static const struct tnt tnts[] = {
* 'O' - Out-of-tree module has been loaded.
* 'E' - Unsigned module has been loaded.
* 'L' - A soft lockup has previously occurred.
+ * 'K' - Kernel has been live patched.
*
* The string is overwritten by the next call to print_tainted().
*/
diff --git a/samples/Kconfig b/samples/Kconfig
index 6181c2cc9ca0..224ebb46bed5 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -63,4 +63,11 @@ config SAMPLE_RPMSG_CLIENT
to communicate with an AMP-configured remote processor over
the rpmsg bus.
+config SAMPLE_LIVEPATCH
+ tristate "Build live patching sample -- loadable modules only"
+ depends on LIVEPATCH && m
+ help
+ Builds a sample live patch that replaces the procfs handler
+ for /proc/cmdline to print "this has been live patched".
+
endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index 1a60c62e2045..f00257bcc5a7 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,4 @@
# Makefile for Linux samples code
-obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ \
+obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \
hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/
diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile
new file mode 100644
index 000000000000..10319d7ea0b1
--- /dev/null
+++ b/samples/livepatch/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o
diff --git a/samples/livepatch/livepatch-sample.c b/samples/livepatch/livepatch-sample.c
new file mode 100644
index 000000000000..fb8c8614e728
--- /dev/null
+++ b/samples/livepatch/livepatch-sample.c
@@ -0,0 +1,91 @@
+/*
+ * livepatch-sample.c - Kernel Live Patching Sample Module
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@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/>.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/livepatch.h>
+
+/*
+ * This (dumb) live patch overrides the function that prints the
+ * kernel boot cmdline when /proc/cmdline is read.
+ *
+ * Example:
+ *
+ * $ cat /proc/cmdline
+ * <your cmdline>
+ *
+ * $ insmod livepatch-sample.ko
+ * $ cat /proc/cmdline
+ * this has been live patched
+ *
+ * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
+ * $ cat /proc/cmdline
+ * <your cmdline>
+ */
+
+#include <linux/seq_file.h>
+static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
+{
+ seq_printf(m, "%s\n", "this has been live patched");
+ return 0;
+}
+
+static struct klp_func funcs[] = {
+ {
+ .old_name = "cmdline_proc_show",
+ .new_func = livepatch_cmdline_proc_show,
+ }, { }
+};
+
+static struct klp_object objs[] = {
+ {
+ /* name being NULL means vmlinux */
+ .funcs = funcs,
+ }, { }
+};
+
+static struct klp_patch patch = {
+ .mod = THIS_MODULE,
+ .objs = objs,
+};
+
+static int livepatch_init(void)
+{
+ int ret;
+
+ 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_exit(void)
+{
+ WARN_ON(klp_disable_patch(&patch));
+ WARN_ON(klp_unregister_patch(&patch));
+}
+
+module_init(livepatch_init);
+module_exit(livepatch_exit);
+MODULE_LICENSE("GPL");