[PATCH v2 3/3] arm: Add support for function error injection
From: Leo Yan <hidden>
Date: 2019-08-06 10:01:24
Also in:
bpf, linux-arch, linux-arm-kernel, linuxppc-dev, lkml
Subsystem:
arm port, ptrace support, the rest · Maintainers:
Russell King, Oleg Nesterov, Linus Torvalds
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. Signed-off-by: Leo Yan <redacted> --- 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