On Tue, Jul 16, 2019 at 07:13:00PM +0800, Leo Yan wrote:
> This patch implement regs_set_return_value() and
> override_function_with_return() to support function error injection
> for arm64.
>
> In the exception flow, arm64's general register x30 contains the value
> for the link register; so we can just update pt_regs::pc with it rather
> than redirecting execution to a dummy function that returns.
>
> This patch is heavily inspired by the commit 7cd01b08d35f ("powerpc:
> Add support for function error injection").
>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/error-injection.h | 13 +++++++++++++
> arch/arm64/include/asm/ptrace.h | 5 +++++
> arch/arm64/lib/Makefile | 2 ++
> arch/arm64/lib/error-inject.c | 19 +++++++++++++++++++
> 5 files changed, 40 insertions(+)
> create mode 100644 arch/arm64/include/asm/error-injection.h
> create mode 100644 arch/arm64/lib/error-inject.c
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 697ea0510729..a6d9e622977d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -142,6 +142,7 @@ config ARM64
> select HAVE_EFFICIENT_UNALIGNED_ACCESS
> select HAVE_FTRACE_MCOUNT_RECORD
> select HAVE_FUNCTION_TRACER
> + select HAVE_FUNCTION_ERROR_INJECTION
> select HAVE_FUNCTION_GRAPH_TRACER
> select HAVE_GCC_PLUGINS
> select HAVE_HW_BREAKPOINT if PERF_EVENTS
> diff --git a/arch/arm64/include/asm/error-injection.h b/arch/arm64/include/asm/error-injection.h
> new file mode 100644
> index 000000000000..da057e8ed224
> --- /dev/null
> +++ b/arch/arm64/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_ */
Why isn't this prototype in the asm-generic header? Seems weird to have to
duplicate it for each architecture.
> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
> index dad858b6adc6..3aafbbe218a2 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -294,6 +294,11 @@ static inline unsigned long regs_return_value(struct pt_regs *regs)
> return regs->regs[0];
> }
>
> +static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
> +{
> + regs->regs[0] = rc;
> +}
> +
> /**
> * regs_get_kernel_argument() - get Nth function argument in kernel
> * @regs: pt_regs of that context
> diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
> index 33c2a4abda04..f182ccb0438e 100644
> --- a/arch/arm64/lib/Makefile
> +++ b/arch/arm64/lib/Makefile
> @@ -33,3 +33,5 @@ UBSAN_SANITIZE_atomic_ll_sc.o := n
> lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o
>
> obj-$(CONFIG_CRC32) += crc32.o
> +
> +obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
> diff --git a/arch/arm64/lib/error-inject.c b/arch/arm64/lib/error-inject.c
> new file mode 100644
> index 000000000000..35661c2de4b0
> --- /dev/null
> +++ b/arch/arm64/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->regs[30]' contains the the link register for the probed
extra "the"
> + * function and assign it to 'regs->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.
directly
> + */
> + regs->pc = regs->regs[30];
I suppose we could be all fancy and do:
instruction_pointer_set(regs, procedure_link_pointer(regs));
How about that?
Will
