Re: [PATCH v2 2/2] arm64: implement live patching

From: Paul Gortmaker
Date: Fri Jul 15 2016 - 12:03:46 EST


On Mon, Jun 27, 2016 at 11:17 AM, Torsten Duwe <duwe@xxxxxx> wrote:
> On top of FTRACE_WITH_REGS and the klp changes that go into v4.7
> this is straightforward.
>
> Signed-off-by: Torsten Duwe <duwe@xxxxxxx>
> ---
> arch/arm64/Kconfig | 3 +++
> arch/arm64/include/asm/livepatch.h | 37 +++++++++++++++++++++++++++++++++++++
> arch/arm64/kernel/entry-ftrace.S | 13 +++++++++++++
> 3 files changed, 53 insertions(+)
> create mode 100644 arch/arm64/include/asm/livepatch.h
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 36a0e26..cb5adf3 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -80,6 +80,7 @@ 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_PATA_PLATFORM
> @@ -1042,4 +1043,6 @@ if CRYPTO
> source "arch/arm64/crypto/Kconfig"
> endif
>
> +source "kernel/livepatch/Kconfig"
> +
> source "lib/Kconfig"
> diff --git a/arch/arm64/include/asm/livepatch.h b/arch/arm64/include/asm/livepatch.h
> new file mode 100644
> index 0000000..6b9a3d1
> --- /dev/null
> +++ b/arch/arm64/include/asm/livepatch.h
> @@ -0,0 +1,37 @@
> +/*
> + * livepatch.h - arm64-specific Kernel Live Patching Core
> + *
> + * Copyright (C) 2016 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>

These includes don't look right. It would seem all you need is the one
for struct pt_regs.

Paul.
--

> +
> +#ifdef CONFIG_LIVEPATCH
> +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 /* CONFIG_LIVEPATCH */
> +
> +#endif /* _ASM_ARM64_LIVEPATCH_H */
> diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
> index 3ebe791..b166cbf 100644
> --- a/arch/arm64/kernel/entry-ftrace.S
> +++ b/arch/arm64/kernel/entry-ftrace.S
> @@ -204,6 +204,9 @@ ENTRY(ftrace_caller)
> str x9, [sp, #S_LR]
> /* The program counter just after the ftrace call site */
> str lr, [sp, #S_PC]
> +#if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER)
> + mov x19,lr /* remember old return address */
> +#endif
> /* The stack pointer as it was on ftrace_caller entry... */
> add x29, sp, #S_FRAME_SIZE+16 /* ...is also our new FP */
> str x29, [sp, #S_SP]
> @@ -219,6 +222,16 @@ 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?
> + */
> + ldr x9, [sp, #S_PC]
> + cmp x9, x19 /* compare with the value we remembered */
> + /* to not call graph tracer's "call" mechanism twice! */
> + b.eq ftrace_regs_return
> +#endif
> +
> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> .global ftrace_graph_call
> ftrace_graph_call: // ftrace_graph_caller();
> --
> 2.6.6
>
> --
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