On 26 October 2018 at 16:21, Torsten Duwe <duwe@xxxxxx> wrote: > 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 > @@ -120,6 +120,7 @@ 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 > select HAVE_MEMBLOCK_NODE_MAP if NUMA > select HAVE_NMI > @@ -1350,4 +1351,6 @@ if CRYPTO > source "arch/arm64/crypto/Kconfig" > endif > > +source "kernel/livepatch/Kconfig" > + > source "lib/Kconfig" > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -76,6 +76,7 @@ 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 > @@ -94,6 +95,7 @@ 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) > @@ -106,7 +108,8 @@ 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 > @@ -226,6 +226,7 @@ ftrace_common: > > /* The program counter just after the ftrace call site */ > str lr, [x9, #S_PC] > + > /* The stack pointer as it was on ftrace_caller entry... */ > add x28, fp, #16 > str x28, [x9, #S_SP] Please drop this hunk > @@ -233,6 +234,10 @@ ftrace_common: > ldr x28, [fp, 8] > str x28, [x9, #S_LR] /* to pt_regs.r[30] */ > > +#if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER) > + mov x28, lr /* remember old return address */ > +#endif > + > ldr_l x2, function_trace_op, x0 > ldr x1, [fp, #8] > sub x0, lr, #8 /* function entry == IP */ > @@ -245,6 +250,17 @@ ftrace_call: > > bl ftrace_stub > > +#if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER) > + /* Is the trace function a live patcher an has messed with > + * the return address? > + */ > + add x9, sp, #16 /* advance to pt_regs for restore */ > + ldr x0, [x9, #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 Is ftrace_common_return guaranteed to be in range? Conditional branches have only -/+ 1 MB range IIRC. Better to do b.eq ftrace_graph_call b ftrace_common_return to be sure > +#endif > + > #ifdef CONFIG_FUNCTION_GRAPH_TRACER Can we fold these #ifdef blocks together (i.e, incorporate the conditional livepatch sequence here) > .global ftrace_graph_call > ftrace_graph_call: // 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> > > @@ -934,6 +935,9 @@ 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); >
