Hi Russell,
On Tue, Aug 06, 2019 at 06:00:15PM +0800, Leo Yan wrote:
> This patch implements arm specific functions regs_set_return_value() and
> override_function_with_return() to support function error injection.
>
> In the exception flow, it updates pt_regs::ARM_pc with pt_regs::ARM_lr
> so can override the probed function return.
Gentle ping ... Could you review this patch?
Thanks,
Leo.
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
> arch/arm/Kconfig | 1 +
> arch/arm/include/asm/ptrace.h | 5 +++++
> arch/arm/lib/Makefile | 2 ++
> arch/arm/lib/error-inject.c | 19 +++++++++++++++++++
> 4 files changed, 27 insertions(+)
> create mode 100644 arch/arm/lib/error-inject.c
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 33b00579beff..2d3d44a037f6 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -77,6 +77,7 @@ config ARM
> select HAVE_EXIT_THREAD
> select HAVE_FAST_GUP if ARM_LPAE
> select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
> + select HAVE_FUNCTION_ERROR_INJECTION if !THUMB2_KERNEL
> select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
> select HAVE_FUNCTION_TRACER if !XIP_KERNEL
> select HAVE_GCC_PLUGINS
> diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
> index 91d6b7856be4..3b41f37b361a 100644
> --- a/arch/arm/include/asm/ptrace.h
> +++ b/arch/arm/include/asm/ptrace.h
> @@ -89,6 +89,11 @@ static inline long regs_return_value(struct pt_regs *regs)
> return regs->ARM_r0;
> }
>
> +static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
> +{
> + regs->ARM_r0 = rc;
> +}
> +
> #define instruction_pointer(regs) (regs)->ARM_pc
>
> #ifdef CONFIG_THUMB2_KERNEL
> diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
> index b25c54585048..8f56484a7156 100644
> --- a/arch/arm/lib/Makefile
> +++ b/arch/arm/lib/Makefile
> @@ -42,3 +42,5 @@ ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
> CFLAGS_xor-neon.o += $(NEON_FLAGS)
> obj-$(CONFIG_XOR_BLOCKS) += xor-neon.o
> endif
> +
> +obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
> diff --git a/arch/arm/lib/error-inject.c b/arch/arm/lib/error-inject.c
> new file mode 100644
> index 000000000000..2d696dc94893
> --- /dev/null
> +++ b/arch/arm/lib/error-inject.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/error-injection.h>
> +#include <linux/kprobes.h>
> +
> +void override_function_with_return(struct pt_regs *regs)
> +{
> + /*
> + * 'regs' represents the state on entry of a predefined function in
> + * the kernel/module and which is captured on a kprobe.
> + *
> + * 'regs->ARM_lr' contains the the link register for the probed
> + * function, when kprobe returns back from exception it will override
> + * the end of probed function and directly return to the predefined
> + * function's caller.
> + */
> + instruction_pointer_set(regs, regs->ARM_lr);
> +}
> +NOKPROBE_SYMBOL(override_function_with_return);
> --
> 2.17.1
>
