linux-kernel - Re: [PATCH v2] riscv: fix kprobe __user string arg print fault issue

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Message-ID: <87cz3g39we.fsf@all.your.base.are.belong.to.us>
Date:   Thu, 04 May 2023 08:09:37 +0200
From:   Björn Töpel <bjorn@...nel.org>
To:     ruanjinjie <ruanjinjie@...wei.com>, paul.walmsley@...ive.com,
        palmer@...belt.com, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     ruanjinjie@...wei.com
Subject: Re: [PATCH v2] riscv: fix kprobe __user string arg print fault issue

ruanjinjie <ruanjinjie@...wei.com> writes:

> On riscv qemu platform, when add kprobe event on do_sys_open() to show
> filename string arg, it just print fault as follow:
>
> echo 'p:myprobe do_sys_open dfd=$arg1 filename=+0($arg2):string flags=$arg3
> mode=$arg4' > kprobe_events
>
> bash-166     [000] ...1.   360.195367: myprobe: (do_sys_open+0x0/0x84)
> dfd=0xffffffffffffff9c filename=(fault) flags=0x8241 mode=0x1b6
>
> bash-166     [000] ...1.   360.219369: myprobe: (do_sys_open+0x0/0x84)
> dfd=0xffffffffffffff9c filename=(fault) flags=0x8241 mode=0x1b6
>
> bash-191     [000] ...1.   360.378827: myprobe: (do_sys_open+0x0/0x84)
> dfd=0xffffffffffffff9c filename=(fault) flags=0x98800 mode=0x0
>
> As riscv do not select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE,
> the +0($arg2) addr is processed as a kernel address though it is a
> userspace address, cause the above filename=(fault) print. So select
> ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE to avoid the issue, after that the
> kprobe trace is ok as below:
>
> bash-166     [000] ...1.    96.767641: myprobe: (do_sys_open+0x0/0x84)
> dfd=0xffffffffffffff9c filename="/dev/null" flags=0x8241 mode=0x1b6
>
> bash-166     [000] ...1.    96.793751: myprobe: (do_sys_open+0x0/0x84)
> dfd=0xffffffffffffff9c filename="/dev/null" flags=0x8241 mode=0x1b6
>
> bash-177     [000] ...1.    96.962354: myprobe: (do_sys_open+0x0/0x84)
> dfd=0xffffffffffffff9c filename="/sys/kernel/debug/tracing/events/kprobes/"
> flags=0x98800 mode=0x0
>
> Signed-off-by: ruanjinjie <ruanjinjie@...wei.com>

Please use your full name.

> ---
> v2:
> - add the config in alphabetical order
> ---
>  arch/riscv/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index eb7f29a412f8..b462ed7d41fe 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -25,6 +25,7 @@ config RISCV
>  	select ARCH_HAS_GIGANTIC_PAGE
>  	select ARCH_HAS_KCOV
>  	select ARCH_HAS_MMIOWB
> +	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE

After adding proper name in SoB, feel free to add:

Acked-by: Björn Töpel <bjorn@...osinc.com>

>  	select ARCH_HAS_PMEM_API
>  	select ARCH_HAS_PTE_SPECIAL
>  	select ARCH_HAS_SET_DIRECT_MAP if MMU
> -- 
> 2.25.1