On Mon, 1 Oct 2018, Torsten Duwe wrote: > Based on ftrace with regs, do the usual thing. Also allocate a > task flag for whatever consistency handling will be used. > Watch out for interactions with the graph tracer. Similar to what Mark wrote about 2/4, I'd appreciate a better commit log. Could you explain traditional "what/why/how", please? > Signed-off-by: Torsten Duwe <duwe@xxxxxxx> > > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -119,6 +119,7 @@ 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 > @@ -1349,4 +1350,6 @@ 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) Could you add a note to the changelog what this means? My ability to read arm64 entry.S is very limited, but I can see that _TIF_WORK_MASK is process in a syscall exit and irq return paths. That's good. It is also called (via "b ret_to_user") in a couple of different places (el0_* labels). I guess those are returns from exception handling. A comment about it in the changelog would be appreciated. > #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 +1,36 @@ > +/* 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 <linux/module.h> > +#include <linux/ftrace.h> I think that only #include <asm/ptrace.h> is in fact needed, because of "struct pt_regs". Ad relocations. I checked that everything in struct mod_arch_specific stays after the module is load. Both core and init get SHF_ALLOC set (mod->arch.core.plt->sh_flags in module_frob_arch_sections(). It is important because apply_relocate_add() may use those sections through module_emit_plt_entry() call. ftrace_trampoline section gets SHF_ALLOC as well. Btw, don't you want to do something similar for new ftrace_regs_trampoline in module_frob_arch_sections()? Perhaps even edit arch/arm64/kernel/module.lds? I'm completely clueless here, so it may be ok. And it applies to 2/4 patch. The last thing is count_plts() function called from module_frob_arch_sections(). It needed to be changed in 2016 as well. See Jessica's patch (20160713001113.GA30925@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx). The logic in the function has changed since then. If I am not mistaken, count_plts() is fine as it is right now. It does not consider SHN_UNDEF anymore, it looks at the destination section (where a symbol should resolved to) only. Jessica, could you doublecheck, please? Torsten, please doublecheck all this as well and add a comment about all this to the changelog, so we don't have to analyze it from the beginning again in the future. Thanks, Miroslav
