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From:   Huacai Chen <chenhuacai@kernel.org>
Date:   Sat, 11 Mar 2023 09:15:59 +0800
Message-ID: <CAAhV-H4wQyam2YoGZFnw8Z-tLZJvEHrdfNu1+Yb6Cbs1aKi=bQ@mail.gmail.com>
Subject: Re: [PATCH] LoongArch: Add support for function error injection
To:     Masami Hiramatsu <mhiramat@kernel.org>
Cc:     Tiezhu Yang <yangtiezhu@loongson.cn>,
        WANG Xuerui <kernel@xen0n.name>, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org, loongson-kernel@lists.loongnix.cn
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Queued for loongarch-next, thanks.

Huacai

On Fri, Mar 10, 2023 at 11:22=E2=80=AFPM Masami Hiramatsu <mhiramat@kernel.=
org> wrote:
>
> On Fri, 10 Mar 2023 10:07:09 +0800
> Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> > This feature is related with kprobes, add Masami to CC.
> >
> > On 03/07/2023 03:10 PM, Tiezhu Yang wrote:
> > > Inspired by the commit 42d038c4fb00 ("arm64: Add support for function=
 error
> > > injection") and commit ee55ff803b38 ("riscv: Add support for function=
 error
> > > injection"), support function error injection for LoongArch.
> > >
> > > Mainly implement two functions:
> > > (1) regs_set_return_value() which is used to overwrite the return val=
ue,
> > > (2) override_function_with_return() which is used to override the pro=
bed
> > > function returning and jump to its caller.
> > >
> > > Here is a simple test under CONFIG_FUNCTION_ERROR_INJECTION and
> > > CONFIG_FAIL_FUNCTION:
> > >
> > >   # echo sys_clone > /sys/kernel/debug/fail_function/inject
> > >   # echo 100 > /sys/kernel/debug/fail_function/probability
> > >   # dmesg
> > >   bash: fork: Invalid argument
> > >   # dmesg
> > >   ...
> > >   FAULT_INJECTION: forcing a failure.
> > >   name fail_function, interval 1, probability 100, space 0, times 1
> > >   ...
> > >   Call Trace:
> > >   [<90000000002238f4>] show_stack+0x5c/0x180
> > >   [<90000000012e384c>] dump_stack_lvl+0x60/0x88
> > >   [<9000000000b1879c>] should_fail_ex+0x1b0/0x1f4
> > >   [<900000000032ead4>] fei_kprobe_handler+0x28/0x6c
> > >   [<9000000000230970>] kprobe_breakpoint_handler+0xf0/0x118
> > >   [<90000000012e3e60>] do_bp+0x2c4/0x358
> > >   [<9000000002241924>] exception_handlers+0x1924/0x10000
> > >   [<900000000023b7d0>] sys_clone+0x0/0x4
> > >   [<90000000012e4744>] do_syscall+0x7c/0x94
> > >   [<9000000000221e44>] handle_syscall+0xc4/0x160
> > >
> > > Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
>
> Thanks for porting! This looks good to me.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Thanks!
>
> > > ---
> > >  arch/loongarch/Kconfig              |  1 +
> > >  arch/loongarch/include/asm/ptrace.h |  6 ++++++
> > >  arch/loongarch/lib/Makefile         |  2 ++
> > >  arch/loongarch/lib/error-inject.c   | 10 ++++++++++
> > >  4 files changed, 19 insertions(+)
> > >  create mode 100644 arch/loongarch/lib/error-inject.c
> > >
> > > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> > > index 7fd5125..b16ff7e 100644
> > > --- a/arch/loongarch/Kconfig
> > > +++ b/arch/loongarch/Kconfig
> > > @@ -99,6 +99,7 @@ config LOONGARCH
> > >     select HAVE_FAST_GUP
> > >     select HAVE_FTRACE_MCOUNT_RECORD
> > >     select HAVE_FUNCTION_ARG_ACCESS_API
> > > +   select HAVE_FUNCTION_ERROR_INJECTION
> > >     select HAVE_FUNCTION_GRAPH_TRACER
> > >     select HAVE_FUNCTION_TRACER
> > >     select HAVE_GENERIC_VDSO
> > > diff --git a/arch/loongarch/include/asm/ptrace.h b/arch/loongarch/inc=
lude/asm/ptrace.h
> > > index d761db9..db7332a 100644
> > > --- a/arch/loongarch/include/asm/ptrace.h
> > > +++ b/arch/loongarch/include/asm/ptrace.h
> > > @@ -154,6 +154,12 @@ static inline long regs_return_value(struct pt_r=
egs *regs)
> > >     return regs->regs[4];
> > >  }
> > >
> > > +static inline void regs_set_return_value(struct pt_regs *regs,
> > > +                                    unsigned long val)
> > > +{
> > > +   regs->regs[4] =3D val;
> > > +}
> > > +
> > >  #define instruction_pointer(regs) ((regs)->csr_era)
> > >  #define profile_pc(regs) instruction_pointer(regs)
> > >
> > > diff --git a/arch/loongarch/lib/Makefile b/arch/loongarch/lib/Makefil=
e
> > > index 40bde63..30b1595 100644
> > > --- a/arch/loongarch/lib/Makefile
> > > +++ b/arch/loongarch/lib/Makefile
> > > @@ -5,3 +5,5 @@
> > >
> > >  lib-y      +=3D delay.o memset.o memcpy.o memmove.o \
> > >        clear_user.o copy_user.o dump_tlb.o unaligned.o
> > > +
> > > +obj-$(CONFIG_FUNCTION_ERROR_INJECTION) +=3D error-inject.o
> > > diff --git a/arch/loongarch/lib/error-inject.c b/arch/loongarch/lib/e=
rror-inject.c
> > > new file mode 100644
> > > index 0000000..afc9e1c
> > > --- /dev/null
> > > +++ b/arch/loongarch/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->regs[1]);
> > > +}
> > > +NOKPROBE_SYMBOL(override_function_with_return);
> > >
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>