[PATCH v2 3/3] arm: Add support for function error injection

[Leo Yan]

Hi Russell,

On Thu, Aug 29, 2019 at 07:57:29AM +0100, Russell King - ARM Linux admin wrote:
> I'm sorry, I can't apply this, it produces loads of:
> 
> include/linux/error-injection.h:7:10: fatal error: asm/error-injection.h: No such file or directory
> 
> Since your patch 1 has been merged by the ARM64 people, I can't take
> it until next cycle.

For this case, do you want me to resend this patch in next merge
window?  Or you have picked up this patch but will send PR in next
cycle?

Thanks,
Leo Yan

> On Mon, Aug 19, 2019 at 05:18:08PM +0800, Leo Yan wrote:
> > 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 at linaro.org>
> > > ---
> > >  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
> > > 
> > 
> 
> -- 
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