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Message-ID: <546EA5DC.6000207@hitachi.com>
Date: Fri, 21 Nov 2014 11:39:24 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Seth Jennings <sjenning@...hat.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>,
Jiri Kosina <jkosina@...e.cz>,
Vojtech Pavlik <vojtech@...e.cz>,
Steven Rostedt <rostedt@...dmis.org>,
Petr Mladek <pmladek@...e.cz>, Miroslav Benes <mbenes@...e.cz>,
Christoph Hellwig <hch@...radead.org>,
Greg KH <gregkh@...uxfoundation.org>,
Andy Lutomirski <luto@...capital.net>,
live-patching@...r.kernel.org, x86@...nel.org, kpatch@...hat.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 2/3] kernel: add support for live patching
(2014/11/21 7:29), Seth Jennings wrote:
> This commit introduces code for the live patching core. It implements
> an ftrace-based mechanism and kernel interface for doing live patching
> of kernel and kernel module functions.
>
> It represents the greatest common functionality set between kpatch and
> kgraft and can accept patches built using either method.
>
> This first version does not implement any consistency mechanism that
> ensures that old and new code do not run together. In practice, ~90% of
> CVEs are safe to apply in this way, since they simply add a conditional
> check. However, any function change that can not execute safely with
> the old version of the function can _not_ be safely applied in this
> version.
Thanks for updating :)
BTW, this still have some LPC_XXX macros, those should be KLP_XXX.
Also, as I sent a series of IPMODIFY patches (just now), could you consider
to use the flag? :)
Thank you,
>
> Signed-off-by: Seth Jennings <sjenning@...hat.com>
> ---
> MAINTAINERS | 12 +
> arch/x86/Kconfig | 3 +
> arch/x86/include/asm/livepatch.h | 37 ++
> arch/x86/kernel/Makefile | 1 +
> arch/x86/kernel/livepatch.c | 74 ++++
> include/linux/livepatch.h | 96 +++++
> kernel/Makefile | 1 +
> kernel/livepatch/Kconfig | 18 +
> kernel/livepatch/Makefile | 3 +
> kernel/livepatch/core.c | 828 +++++++++++++++++++++++++++++++++++++++
> 10 files changed, 1073 insertions(+)
> create mode 100644 arch/x86/include/asm/livepatch.h
> create mode 100644 arch/x86/kernel/livepatch.c
> create mode 100644 include/linux/livepatch.h
> create mode 100644 kernel/livepatch/Kconfig
> create mode 100644 kernel/livepatch/Makefile
> create mode 100644 kernel/livepatch/core.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4861577..c7f49ae 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5715,6 +5715,18 @@ F: Documentation/misc-devices/lis3lv02d
> F: drivers/misc/lis3lv02d/
> F: drivers/platform/x86/hp_accel.c
>
> +LIVE PATCHING
> +M: Josh Poimboeuf <jpoimboe@...hat.com>
> +M: Seth Jennings <sjenning@...hat.com>
> +M: Jiri Kosina <jkosina@...e.cz>
> +M: Vojtech Pavlik <vojtech@...e.cz>
> +S: Maintained
> +F: kernel/livepatch/
> +F: include/linux/livepatch.h
> +F: arch/x86/include/asm/livepatch.h
> +F: arch/x86/kernel/livepatch.c
> +L: live-patching@...r.kernel.org
> +
> LLC (802.2)
> M: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> S: Maintained
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ec21dfd..78715fd 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 ARCH_HAVE_LIVE_PATCHING
>
> ### Arch settings
> config X86
> @@ -1991,6 +1992,8 @@ 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 0000000..2ed86ec
> --- /dev/null
> +++ b/arch/x86/include/asm/livepatch.h
> @@ -0,0 +1,37 @@
> +/*
> + * livepatch.h - x86-specific Kernel Live Patching Core
> + *
> + * Copyright (C) 2014 Seth Jennings <sjenning@...hat.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/>.
> + */
> +
> +#ifndef _ASM_X86_LIVEPATCH_H
> +#define _ASM_X86_LIVEPATCH_H
> +
> +#include <linux/module.h>
> +
> +#ifdef CONFIG_LIVE_PATCHING
> +extern int klp_write_module_reloc(struct module *mod, unsigned long type,
> + unsigned long loc, unsigned long value);
> +
> +#else
> +static int klp_write_module_reloc(struct module *mod, unsigned long type,
> + unsigned long loc, unsigned long value)
> +{
> + return -ENOSYS;
> +}
> +#endif
> +
> +#endif /* _ASM_X86_LIVEPATCH_H */
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 5d4502c..316b34e 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_LIVE_PATCHING) += 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 0000000..777a4a4
> --- /dev/null
> +++ b/arch/x86/kernel/livepatch.c
> @@ -0,0 +1,74 @@
> +/*
> + * livepatch.c - x86-specific Kernel Live Patching Core
> + *
> + * Copyright (C) 2014 Seth Jennings <sjenning@...hat.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/uaccess.h>
> +#include <asm/cacheflush.h>
> +#include <asm/page_types.h>
> +
> +int klp_write_module_reloc(struct module *mod, unsigned long type,
> + unsigned long loc, unsigned long value)
> +{
> + int ret, readonly, numpages, size = 4;
> + 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_ro_size)
> + readonly = 1;
> + else if (loc >= core + core_ro_size && loc < core + core_size)
> + readonly = 0;
> + else
> + /* loc not in expected range */
> + return -EINVAL;
> +
> + 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/livepatch.h b/include/linux/livepatch.h
> new file mode 100644
> index 0000000..eab84df
> --- /dev/null
> +++ b/include/linux/livepatch.h
> @@ -0,0 +1,96 @@
> +/*
> + * livepatch.h - Kernel Live Patching Core
> + *
> + * Copyright (C) 2014 Seth Jennings <sjenning@...hat.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/>.
> + */
> +
> +#ifndef _LINUX_LIVEPATCH_H_
> +#define _LINUX_LIVEPATCH_H_
> +
> +#include <linux/module.h>
> +#include <linux/ftrace.h>
> +
> +#if IS_ENABLED(CONFIG_LIVE_PATCHING)
> +
> +#include <asm/livepatch.h>
> +
> +/* TODO: add kernel-doc for structures once agreed upon */
> +
> +enum klp_state {
> + LPC_DISABLED,
> + LPC_ENABLED
> +};
> +
> +struct klp_func {
> + /* external */
> + const char *old_name; /* function to be patched */
> + void *new_func; /* replacement function in patch module */
> + /*
> + * 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;
> + struct ftrace_ops fops;
> + enum klp_state state;
> +};
> +
> +struct klp_reloc {
> + unsigned long dest;
> + unsigned long src;
> + unsigned long type;
> + const char *name;
> + int addend;
> + int external;
> +};
> +
> +struct klp_object {
> + /* external */
> + const char *name; /* "vmlinux" or module name */
> + struct klp_reloc *relocs;
> + struct klp_func *funcs;
> +
> + /* internal */
> + struct kobject *kobj;
> + struct module *mod; /* module associated with object */
> + enum klp_state state;
> +};
> +
> +struct klp_patch {
> + /* external */
> + struct module *mod; /* module containing the patch */
> + 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_LIVE_PATCHING */
> +
> +#endif /* _LINUX_LIVEPATCH_H_ */
> diff --git a/kernel/Makefile b/kernel/Makefile
> index a59481a..616994f 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-$(CONFIG_FREEZER) += freezer.o
> diff --git a/kernel/livepatch/Kconfig b/kernel/livepatch/Kconfig
> new file mode 100644
> index 0000000..96da00f
> --- /dev/null
> +++ b/kernel/livepatch/Kconfig
> @@ -0,0 +1,18 @@
> +config ARCH_HAVE_LIVE_PATCHING
> + boolean
> + help
> + Arch supports kernel live patching
> +
> +config LIVE_PATCHING
> + boolean "Kernel Live Patching"
> + depends on DYNAMIC_FTRACE_WITH_REGS
> + depends on MODULES
> + depends on SYSFS
> + depends on KALLSYMS_ALL
> + depends on ARCH_HAVE_LIVE_PATCHING
> + help
> + Say Y here if you want to support kernel live patching.
> + This option has no runtime impact until a kernel "patch"
> + module uses the interface provided by this option to register
> + a patch, causing calls to patched functions to be redirected
> + to new function code contained in the patch module.
> diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile
> new file mode 100644
> index 0000000..7c1f008
> --- /dev/null
> +++ b/kernel/livepatch/Makefile
> @@ -0,0 +1,3 @@
> +obj-$(CONFIG_LIVE_PATCHING) += livepatch.o
> +
> +livepatch-objs := core.o
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> new file mode 100644
> index 0000000..9140e42
> --- /dev/null
> +++ b/kernel/livepatch/core.c
> @@ -0,0 +1,828 @@
> +/*
> + * core.c - Kernel Live Patching Core
> + *
> + * Copyright (C) 2014 Seth Jennings <sjenning@...hat.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/>.
> + */
> +
> +#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>
> +
> +/*************************************
> + * Core structures
> + ************************************/
> +
> +static DEFINE_MUTEX(klp_mutex);
> +static LIST_HEAD(klp_patches);
> +
> +/*******************************************
> + * Helpers
> + *******************************************/
> +
> +/* sets obj->mod if object is not vmlinux and module is found */
> +static bool klp_find_object_module(struct klp_object *obj)
> +{
> + if (!strcmp(obj->name, "vmlinux"))
> + return 1;
> +
> + 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);
> +
> + return !!obj->mod;
> +}
> +
> +/************************************
> + * kallsyms
> + ***********************************/
> +
> +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_symbol() handles this and only returns the
> + * addr if count == 1.
> + */
> + args->addr = addr;
> + args->count++;
> +
> + return 0;
> +}
> +
> +static int klp_find_symbol(const char *objname, const char *name,
> + unsigned long *addr)
> +{
> + struct klp_find_arg args = {
> + .objname = objname,
> + .name = name,
> + .addr = 0,
> + .count = 0
> + };
> +
> + if (objname && !strcmp(objname, "vmlinux"))
> + args.objname = NULL;
> +
> + 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?",
> + name, addr);
> + return -EINVAL;
> +}
> +
> +static int klp_find_verify_func_addr(struct klp_func *func, const char *objname)
> +{
> + int ret;
> +
> +#if defined(CONFIG_RANDOMIZE_BASE)
> + /* KASLR is enabled, disregard old_addr from user */
> + func->old_addr = 0;
> +#endif
> +
> + if (func->old_addr && strcmp(objname, "vmlinux")) {
> + pr_err("old address specified for module symbol\n");
> + return -EINVAL;
> + }
> +
> + if (func->old_addr)
> + ret = klp_verify_vmlinux_symbol(func->old_name,
> + func->old_addr);
> + else
> + ret = klp_find_symbol(objname, func->old_name,
> + &func->old_addr);
> +
> + return ret;
> +}
> +
> +/****************************************
> + * dynamic relocations (load-time linker)
> + ****************************************/
> +
> +/*
> + * 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_symbol(pmod->name, name, addr);
> +}
> +
> +static int klp_write_object_relocations(struct module *pmod,
> + struct klp_object *obj)
> +{
> + int ret;
> + struct klp_reloc *reloc;
> +
> + for (reloc = obj->relocs; reloc->name; reloc++) {
> + if (!strcmp(obj->name, "vmlinux")) {
> + ret = klp_verify_vmlinux_symbol(reloc->name,
> + reloc->src);
> + if (ret)
> + return ret;
> + } else {
> + /* module, reloc->src needs to be discovered */
> + if (reloc->external)
> + ret = klp_find_external_symbol(pmod,
> + reloc->name,
> + &reloc->src);
> + else
> + ret = klp_find_symbol(obj->mod->name,
> + reloc->name,
> + &reloc->src);
> + if (ret)
> + return ret;
> + }
> + ret = klp_write_module_reloc(pmod, reloc->type, reloc->dest,
> + reloc->src + reloc->addend);
> + if (ret) {
> + pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
> + reloc->name, reloc->src, ret);
> + return ret;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/***********************************
> + * ftrace registration
> + **********************************/
> +
> +static void klp_ftrace_handler(unsigned long ip, unsigned long parent_ip,
> + struct ftrace_ops *ops, struct pt_regs *regs)
> +{
> + struct klp_func *func = ops->private;
> +
> + regs->ip = (unsigned long)func->new_func;
> +}
> +
> +static int klp_enable_func(struct klp_func *func)
> +{
> + int ret;
> +
> + if (WARN_ON(!func->old_addr || func->state != LPC_DISABLED))
> + return -EINVAL;
> +
> + ret = ftrace_set_filter_ip(&func->fops, func->old_addr, 0, 0);
> + if (ret) {
> + pr_err("failed to set ftrace filter for function '%s' (%d)\n",
> + func->old_name, ret);
> + return ret;
> + }
> + ret = register_ftrace_function(&func->fops);
> + if (ret) {
> + pr_err("failed to register ftrace handler for function '%s' (%d)\n",
> + func->old_name, ret);
> + ftrace_set_filter_ip(&func->fops, func->old_addr, 1, 0);
> + } else
> + func->state = LPC_ENABLED;
> +
> + return ret;
> +}
> +
> +static int klp_disable_func(struct klp_func *func)
> +{
> + int ret;
> +
> + if (WARN_ON(func->state != LPC_ENABLED))
> + return -EINVAL;
> +
> + if (!func->old_addr)
> + /* parent object is not loaded */
> + return 0;
> + ret = unregister_ftrace_function(&func->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(&func->fops, func->old_addr, 1, 0);
> + if (ret)
> + pr_warn("function unregister succeeded but failed to clear the filter\n");
> + func->state = LPC_DISABLED;
> +
> + return 0;
> +}
> +
> +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 != LPC_ENABLED)
> + continue;
> + ret = klp_disable_func(func);
> + if (ret)
> + return ret;
> + if (strcmp(obj->name, "vmlinux"))
> + func->old_addr = 0;
> + }
> + obj->state = LPC_DISABLED;
> +
> + return 0;
> +}
> +
> +static int klp_enable_object(struct module *pmod, struct klp_object *obj)
> +{
> + struct klp_func *func;
> + int ret;
> +
> + if (WARN_ON(!obj->mod && strcmp(obj->name, "vmlinux")))
> + return -EINVAL;
> +
> + if (obj->relocs) {
> + ret = klp_write_object_relocations(pmod, obj);
> + if (ret)
> + goto unregister;
> + }
> +
> + for (func = obj->funcs; func->old_name; func++) {
> + ret = klp_find_verify_func_addr(func, obj->name);
> + if (ret)
> + goto unregister;
> +
> + ret = klp_enable_func(func);
> + if (ret)
> + goto unregister;
> + }
> + obj->state = LPC_ENABLED;
> +
> + return 0;
> +unregister:
> + WARN_ON(klp_disable_object(obj));
> + return ret;
> +}
> +
> +/******************************
> + * enable/disable
> + ******************************/
> +
> +static int __klp_disable_patch(struct klp_patch *patch)
> +{
> + struct klp_object *obj;
> + int ret;
> +
> + pr_notice("disabling patch '%s'\n", patch->mod->name);
> +
> + for (obj = patch->objs; obj->name; obj++) {
> + if (obj->state != LPC_ENABLED)
> + continue;
> + ret = klp_disable_object(obj);
> + if (ret)
> + return ret;
> + }
> + patch->state = LPC_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);
> + ret = __klp_disable_patch(patch);
> + 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 != LPC_DISABLED))
> + return -EINVAL;
> +
> + 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->name; obj++) {
> + if (!klp_find_object_module(obj))
> + continue;
> + ret = klp_enable_object(patch->mod, obj);
> + if (ret)
> + goto unregister;
> + }
> + patch->state = LPC_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);
> + ret = __klp_enable_patch(patch);
> + mutex_unlock(&klp_mutex);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(klp_enable_patch);
> +
> +/******************************
> + * module notifier
> + *****************************/
> +
> +static void klp_module_notify_coming(struct module *pmod,
> + struct klp_object *obj)
> +{
> + struct module *mod = obj->mod;
> + int ret;
> +
> + pr_notice("applying patch '%s' to loading module '%s'\n",
> + pmod->name, mod->name);
> + obj->mod = mod;
> + ret = klp_enable_object(pmod, obj);
> + if (ret)
> + pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
> + pmod->name, mod->name, ret);
> +}
> +
> +static void klp_module_notify_going(struct module *pmod,
> + struct klp_object *obj)
> +{
> + struct module *mod = obj->mod;
> + int ret;
> +
> + 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);
> + obj->mod = NULL;
> +}
> +
> +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) {
> + if (patch->state == LPC_DISABLED)
> + continue;
> + for (obj = patch->objs; obj->name; obj++) {
> + if (strcmp(obj->name, mod->name))
> + continue;
> + if (action == MODULE_STATE_COMING) {
> + obj->mod = mod;
> + klp_module_notify_coming(patch->mod, obj);
> + } else /* MODULE_STATE_GOING */
> + klp_module_notify_going(patch->mod, 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 */
> +};
> +
> +/********************************************
> + * 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 != LPC_DISABLED && val != LPC_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 == LPC_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 struct kobject *klp_root_kobj;
> +
> +static int klp_create_root_kobj(void)
> +{
> + klp_root_kobj =
> + kobject_create_and_add("livepatch", kernel_kobj);
> + if (!klp_root_kobj)
> + return -ENOMEM;
> + return 0;
> +}
> +
> +static void klp_remove_root_kobj(void)
> +{
> + kobject_put(klp_root_kobj);
> +}
> +
> +static void klp_kobj_release_patch(struct kobject *kobj)
> +{
> + struct klp_patch *patch;
> +
> + patch = container_of(kobj, struct klp_patch, kobj);
> + if (!list_empty(&patch->list))
> + list_del(&patch->list);
> +}
> +
> +static struct kobj_type klp_ktype_patch = {
> + .release = klp_kobj_release_patch,
> + .sysfs_ops = &kobj_sysfs_ops,
> + .default_attrs = klp_patch_attrs
> +};
> +
> +/*********************************
> + * structure allocation
> + ********************************/
> +
> +/*
> + * 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);
> +}
> +
> +/*
> + * 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->name && 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);
> + kobject_put(&patch->kobj);
> +}
> +
> +static int klp_init_funcs(struct klp_object *obj)
> +{
> + struct klp_func *func;
> + struct ftrace_ops *ops;
> +
> + for (func = obj->funcs; func->old_name; func++) {
> + func->state = LPC_DISABLED;
> + ops = &func->fops;
> + ops->private = func;
> + ops->func = klp_ftrace_handler;
> + ops->flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_DYNAMIC;
> +
> + /* sysfs */
> + func->kobj = kobject_create_and_add(func->old_name, obj->kobj);
> + if (!func->kobj)
> + goto free;
> + }
> +
> + return 0;
> +free:
> + klp_free_funcs_limited(obj, func);
> + return -ENOMEM;
> +}
> +
> +static int klp_init_objects(struct klp_patch *patch)
> +{
> + struct klp_object *obj;
> + int ret;
> +
> + for (obj = patch->objs; obj->name; obj++) {
> + /* obj->mod set by klp_object_module_get() */
> + obj->state = LPC_DISABLED;
> +
> + /* sysfs */
> + obj->kobj = kobject_create_and_add(obj->name, &patch->kobj);
> + if (!obj->kobj)
> + goto free;
> +
> + /* init functions */
> + ret = klp_init_funcs(obj);
> + if (ret) {
> + kobject_put(obj->kobj);
> + goto free;
> + }
> + }
> +
> + return 0;
> +free:
> + klp_free_objects_limited(patch, obj);
> + return -ENOMEM;
> +}
> +
> +static int klp_init_patch(struct klp_patch *patch)
> +{
> + int ret;
> +
> + mutex_lock(&klp_mutex);
> +
> + /* init */
> + patch->state = LPC_DISABLED;
> +
> + /* sysfs */
> + ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
> + klp_root_kobj, patch->mod->name);
> + if (ret)
> + return ret;
> +
> + /* create objects */
> + ret = klp_init_objects(patch);
> + if (ret) {
> + kobject_put(&patch->kobj);
> + return ret;
> + }
> +
> + /* add to global list of patches */
> + list_add(&patch->list, &klp_patches);
> +
> + mutex_unlock(&klp_mutex);
> +
> + return 0;
> +}
> +
> +/************************************
> + * register/unregister
> + ***********************************/
> +
> +/**
> + * 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 (!patch || !patch->mod || !patch->objs)
> + 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);
> +
> +/**
> + * 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 (patch->state == LPC_ENABLED) {
> + ret = -EINVAL;
> + goto out;
> + }
> + klp_free_patch(patch);
> +out:
> + mutex_unlock(&klp_mutex);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(klp_unregister_patch);
> +
> +/************************************
> + * entry/exit
> + ************************************/
> +
> +static int klp_init(void)
> +{
> + int ret;
> +
> + ret = register_module_notifier(&klp_module_nb);
> + if (ret)
> + return ret;
> +
> + ret = klp_create_root_kobj();
> + if (ret)
> + goto unregister;
> +
> + return 0;
> +unregister:
> + unregister_module_notifier(&klp_module_nb);
> + return ret;
> +}
> +
> +static void klp_exit(void)
> +{
> + klp_remove_root_kobj();
> + unregister_module_notifier(&klp_module_nb);
> +}
> +
> +module_init(klp_init);
> +module_exit(klp_exit);
> +MODULE_DESCRIPTION("Live Kernel Patching Core");
> +MODULE_LICENSE("GPL");
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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