Based on ftrace with regs, do the usual thing. (see Documentation/livepatch/livepatch.txt) Use task flag bit 6 to track patch transisiton state for the consistency model. Add it to the work mask so it gets cleared on all kernel exits to userland. Tell livepatch regs->pc is the place to change the return address. Make sure the graph tracer call hook is only called on the final function entry in case regs->pc gets modified after an interception. Signed-off-by: Torsten Duwe <duwe@xxxxxxx> --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -142,6 +142,7 @@ config ARM64 select HAVE_GENERIC_DMA_COHERENT select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_IRQ_TIME_ACCOUNTING + select HAVE_LIVEPATCH select HAVE_MEMBLOCK_NODE_MAP if NUMA select HAVE_NMI select HAVE_PATA_PLATFORM @@ -1503,3 +1504,5 @@ source "arch/arm64/kvm/Kconfig" if CRYPTO source "arch/arm64/crypto/Kconfig" endif + +source "kernel/livepatch/Kconfig" --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -87,6 +87,7 @@ void arch_release_task_struct(struct tas #define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */ #define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */ #define TIF_FSCHECK 5 /* Check FS is USER_DS on return */ +#define TIF_PATCH_PENDING 6 #define TIF_NOHZ 7 #define TIF_SYSCALL_TRACE 8 #define TIF_SYSCALL_AUDIT 9 @@ -105,6 +106,7 @@ void arch_release_task_struct(struct tas #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE) +#define _TIF_PATCH_PENDING (1 << TIF_PATCH_PENDING) #define _TIF_NOHZ (1 << TIF_NOHZ) #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) @@ -117,7 +119,8 @@ void arch_release_task_struct(struct tas #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \ - _TIF_UPROBE | _TIF_FSCHECK) + _TIF_UPROBE | _TIF_FSCHECK | \ + _TIF_PATCH_PENDING) #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \ --- /dev/null +++ b/arch/arm64/include/asm/livepatch.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 + * + * livepatch.h - arm64-specific Kernel Live Patching Core + * + * Copyright (C) 2016,2018 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_ARM64_LIVEPATCH_H +#define _ASM_ARM64_LIVEPATCH_H + +#include <asm/ptrace.h> + +static inline int klp_check_compiler_support(void) +{ + return 0; +} + +static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip) +{ + regs->pc = ip; +} + +#endif /* _ASM_ARM64_LIVEPATCH_H */ --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S @@ -244,6 +244,9 @@ ENDPROC(ftrace_caller) ENTRY(ftrace_common) +#if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER) + mov x28, lr /* remember old return address */ +#endif mov x3, sp /* pt_regs are @sp */ ldr_l x2, function_trace_op, x0 mov x1, x9 /* parent IP */ @@ -253,6 +256,16 @@ GLOBAL(ftrace_call) bl ftrace_stub #ifdef CONFIG_FUNCTION_GRAPH_TRACER +#ifdef CONFIG_LIVEPATCH + /* Is the trace function a live patcher an has messed with + * the return address? + */ + ldr x0, [sp, #S_PC] + cmp x0, x28 /* compare with the value we remembered */ + /* to not call graph tracer's "call" mechanism twice! */ + b.ne ftrace_common_return +#endif + GLOBAL(ftrace_graph_call) // ftrace_graph_caller(); nop // If enabled, this will be replaced // "b ftrace_graph_caller" --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -29,6 +29,7 @@ #include <linux/sizes.h> #include <linux/string.h> #include <linux/tracehook.h> +#include <linux/livepatch.h> #include <linux/ratelimit.h> #include <linux/syscalls.h> @@ -937,6 +938,9 @@ asmlinkage void do_notify_resume(struct if (thread_flags & _TIF_UPROBE) uprobe_notify_resume(regs); + if (thread_flags & _TIF_PATCH_PENDING) + klp_update_patch_state(current); + if (thread_flags & _TIF_SIGPENDING) do_signal(regs);
