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From: Leo Yan <leo.yan@linaro.org>
To: Russell King <linux@armlinux.org.uk>,
	Oleg Nesterov <oleg@redhat.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Arnd Bergmann <arnd@arndb.de>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org, Masami Hiramatsu <mhiramat@kernel.org>,
	Justin He <Justin.He@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Subject: [PATCH 2/2] arm: Add support for function error injection
Date: Tue, 16 Jul 2019 19:13:01 +0800
Message-ID: <20190716111301.1855-3-leo.yan@linaro.org> (raw)
In-Reply-To: <20190716111301.1855-1-leo.yan@linaro.org>

This patch implement regs_set_return_value() and
override_function_with_return() to support function error injection
for arm.

In the exception flow, we can update pt_regs::ARM_pc with
pt_regs::ARM_lr so that can override the probed function return.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 arch/arm/Kconfig                       |  1 +
 arch/arm/include/asm/error-injection.h | 13 +++++++++++++
 arch/arm/include/asm/ptrace.h          |  5 +++++
 arch/arm/lib/Makefile                  |  2 ++
 arch/arm/lib/error-inject.c            | 19 +++++++++++++++++++
 5 files changed, 40 insertions(+)
 create mode 100644 arch/arm/include/asm/error-injection.h
 create mode 100644 arch/arm/lib/error-inject.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 8869742a85df..f7932a5e29ea 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -74,6 +74,7 @@ config ARM
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
 	select HAVE_EXIT_THREAD
 	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/error-injection.h b/arch/arm/include/asm/error-injection.h
new file mode 100644
index 000000000000..da057e8ed224
--- /dev/null
+++ b/arch/arm/include/asm/error-injection.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef __ASM_ERROR_INJECTION_H_
+#define __ASM_ERROR_INJECTION_H_
+
+#include <linux/compiler.h>
+#include <linux/linkage.h>
+#include <asm/ptrace.h>
+#include <asm-generic/error-injection.h>
+
+void override_function_with_return(struct pt_regs *regs);
+
+#endif /* __ASM_ERROR_INJECTION_H_ */
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 0bff0176db2c..d3d7430ecd76 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -43,3 +43,5 @@ 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..96319d017114
--- /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 and assign it to 'regs->ARM_pc', so when kprobe returns
+	 * back from exception it will override the end of probed function
+	 * and drirectly return to the predefined function's caller.
+	 */
+	regs->ARM_pc = regs->ARM_lr;
+}
+NOKPROBE_SYMBOL(override_function_with_return);
-- 
2.17.1


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  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-16 11:12 [PATCH 0/2] arm/arm64: " Leo Yan
2019-07-16 11:13 ` [PATCH 1/2] arm64: " Leo Yan
2019-07-25  1:42   ` Leo Yan
2019-07-31 16:08   ` Will Deacon
2019-07-31 16:58     ` Leo Yan
2019-07-16 11:13 ` Leo Yan [this message]
2019-07-25  1:48   ` [PATCH 2/2] arm: " Leo Yan
2019-07-17  7:52 ` [PATCH 0/2] arm/arm64: " Masami Hiramatsu
2019-07-17  8:14   ` Leo Yan

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