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Subject[PATCH v4 8/9] riscv: Add support for function error injection
Date
From: Guo Ren <guoren@linux.alibaba.com>

Inspired by the commit 42d038c4fb00 ("arm64: Add support for function
error injection"), this patch supports function error injection for
riscv.

This patch mainly support two functions: one is regs_set_return_value()
which is used to overwrite the return value; the another function is
override_function_with_return() which is to override the probed
function returning and jump to its caller.

Test log:
cd /sys/kernel/debug/fail_function
echo sys_clone > inject
echo 100 > probability
echo 1 > interval
ls /
[ 313.176875] FAULT_INJECTION: forcing a failure.
[ 313.176875] name fail_function, interval 1, probability 100, space 0, times 1
[ 313.184357] CPU: 0 PID: 87 Comm: sh Not tainted 5.8.0-rc5-00007-g6a758cc #117
[ 313.187616] Call Trace:
[ 313.189100] [<ffffffe0002036b6>] walk_stackframe+0x0/0xc2
[ 313.191626] [<ffffffe00020395c>] show_stack+0x40/0x4c
[ 313.193927] [<ffffffe000556c60>] dump_stack+0x7c/0x96
[ 313.194795] [<ffffffe0005522e8>] should_fail+0x140/0x142
[ 313.195923] [<ffffffe000299ffc>] fei_kprobe_handler+0x2c/0x5a
[ 313.197687] [<ffffffe0009e2ec4>] kprobe_breakpoint_handler+0xb4/0x18a
[ 313.200054] [<ffffffe00020357e>] do_trap_break+0x36/0xca
[ 313.202147] [<ffffffe000201bca>] ret_from_exception+0x0/0xc
[ 313.204556] [<ffffffe000201bbc>] ret_from_syscall+0x0/0x2
-sh: can't fork: Invalid argument

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/ptrace.h | 6 ++++++
arch/riscv/lib/Makefile | 2 ++
arch/riscv/lib/error-inject.c | 10 ++++++++++
4 files changed, 19 insertions(+)
create mode 100644 arch/riscv/lib/error-inject.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 4081ecf..3d094fd 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -66,6 +66,7 @@ config RISCV
select HAVE_EBPF_JIT if MMU
select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_GCC_PLUGINS
+ select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_GENERIC_VDSO if MMU && 64BIT
select HAVE_KPROBES
select HAVE_KPROBES_ON_FTRACE
diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
index 23372bb..cb4abb6 100644
--- a/arch/riscv/include/asm/ptrace.h
+++ b/arch/riscv/include/asm/ptrace.h
@@ -109,6 +109,12 @@ static inline unsigned long regs_return_value(struct pt_regs *regs)
return regs->a0;
}

+static inline void regs_set_return_value(struct pt_regs *regs,
+ unsigned long val)
+{
+ regs->a0 = val;
+}
+
extern int regs_query_register_offset(const char *name);
extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
unsigned int n);
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 0d0db80..04baa93 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -4,3 +4,5 @@ lib-y += memcpy.o
lib-y += memset.o
lib-y += uaccess.o
lib-$(CONFIG_64BIT) += tishift.o
+
+obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
diff --git a/arch/riscv/lib/error-inject.c b/arch/riscv/lib/error-inject.c
new file mode 100644
index 00000000..d667ade
--- /dev/null
+++ b/arch/riscv/lib/error-inject.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/error-injection.h>
+#include <linux/kprobes.h>
+
+void override_function_with_return(struct pt_regs *regs)
+{
+ instruction_pointer_set(regs, regs->ra);
+}
+NOKPROBE_SYMBOL(override_function_with_return);
--
2.7.4
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