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From:   Vitaly Wool <vitaly.wool@konsulko.com>
Date:   Mon, 10 May 2021 20:19:30 +0200
Message-ID: <CAM4kBBJqF=AxTu50PF=EshLSyqn0=yeC2dwf4JJj_Grsi_Tccg@mail.gmail.com>
Subject: Re: [PATCH] riscv: code patching only works on !XIP_KERNEL
To:     Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, May 10, 2021 at 6:35 PM Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:
>
> From: Jisheng Zhang <jszhang@kernel.org>
>
> Some features which need code patching such as KPROBES, DYNAMIC_FTRACE
> KGDB can only work on !XIP_KERNEL. Add dependencies for these features
> that rely on code patching.

Since we can define extra RW sections to place some tiny code bits in
RAM, I would suggest that you hold back this patch for a while.
I am not going to support the idea of e. g. compiling KGDB support
into a XIP kernel, but disabling the whole HAVE_ARCH_JUMP_LABEL is
hardly the way to go.

Best regards,
   Vitaly

> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> Hi,
>
> Currently, the RISCV_ERRATA_ALTERNATIVE also only works on !XIP_KERNEL
> but from the maillist it seem there's effort to make the co-exist, so
> I drop RISCV_ERRATA_ALTERNATIVE dependency on !XIP_KERNEL.
>
> Thanks
>
>  arch/riscv/Kconfig | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index a8ad8eb76120..61320b94ef97 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -60,11 +60,11 @@ config RISCV
>         select GENERIC_TIME_VSYSCALL if MMU && 64BIT
>         select HANDLE_DOMAIN_IRQ
>         select HAVE_ARCH_AUDITSYSCALL
> -       select HAVE_ARCH_JUMP_LABEL
> -       select HAVE_ARCH_JUMP_LABEL_RELATIVE
> +       select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
> +       select HAVE_ARCH_JUMP_LABEL_RELATIVE if !XIP_KERNEL
>         select HAVE_ARCH_KASAN if MMU && 64BIT
>         select HAVE_ARCH_KASAN_VMALLOC if MMU && 64BIT
> -       select HAVE_ARCH_KGDB
> +       select HAVE_ARCH_KGDB if !XIP_KERNEL
>         select HAVE_ARCH_KGDB_QXFER_PKT
>         select HAVE_ARCH_MMAP_RND_BITS if MMU
>         select HAVE_ARCH_SECCOMP_FILTER
> @@ -79,9 +79,9 @@ config RISCV
>         select HAVE_GCC_PLUGINS
>         select HAVE_GENERIC_VDSO if MMU && 64BIT
>         select HAVE_IRQ_TIME_ACCOUNTING
> -       select HAVE_KPROBES
> -       select HAVE_KPROBES_ON_FTRACE
> -       select HAVE_KRETPROBES
> +       select HAVE_KPROBES if !XIP_KERNEL
> +       select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL
> +       select HAVE_KRETPROBES if !XIP_KERNEL
>         select HAVE_PCI
>         select HAVE_PERF_EVENTS
>         select HAVE_PERF_REGS
> @@ -230,11 +230,11 @@ config ARCH_RV64I
>         bool "RV64I"
>         select 64BIT
>         select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && GCC_VERSION >= 50000
> -       select HAVE_DYNAMIC_FTRACE if MMU && $(cc-option,-fpatchable-function-entry=8)
> +       select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8)
>         select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
> -       select HAVE_FTRACE_MCOUNT_RECORD
> +       select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>         select HAVE_FUNCTION_GRAPH_TRACER
> -       select HAVE_FUNCTION_TRACER
> +       select HAVE_FUNCTION_TRACER if !XIP_KERNEL
>         select SWIOTLB if MMU
>
>  endchoice
> --
> 2.31.0
>
>
>
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