Re: [PATCH V2 1/3] riscv: Fixup static_obj() fail

From: Guo Ren <guoren@kernel.org>
To: Atish Patra <atishp@atishpatra.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
	Tycho Andersen <tycho@tycho.ws>,
	Albert Ou <aou@eecs.berkeley.edu>, Nick Hu <nickhu@andestech.com>,
	Anup Patel <anup@brainfault.org>,
	Palmer Dabbelt <palmerdabbelt@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-csky@vger.kernel.org, Guo Ren <guoren@linux.alibaba.com>,
	Zong Li <zong.li@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Greentime Hu <greentime.hu@sifive.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-riscv <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH V2 1/3] riscv: Fixup static_obj() fail
Date: Wed, 7 Oct 2020 00:46:40 +0800	[thread overview]
Message-ID: <CAJF2gTRc-RUBiQ=ZE7BT8tABHu3=Bcmuc+ADyBLZ7r7fozwahg@mail.gmail.com> (raw)
In-Reply-To: <CAOnJCUJhb2K89pRETbfTJ=5jHQhWfyfrOUu8zOE77j+id6OpSA@mail.gmail.com>

On Tue, Oct 6, 2020 at 3:14 AM Atish Patra <atishp@atishpatra.org> wrote:
>
> On Thu, Sep 24, 2020 at 9:19 AM Guo Ren <guoren@kernel.org> wrote:
> >
> > How about this, revert the commit and don't free INIT_DATA_SECTION. I
> > think the solution is safe enough, but wast a little memory.
> >
> > diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> > index f3586e3..34d00d9 100644
> > --- a/arch/riscv/kernel/vmlinux.lds.S
> > +++ b/arch/riscv/kernel/vmlinux.lds.S
> > @@ -22,13 +22,11 @@ SECTIONS
> >         /* Beginning of code and text segment */
> >         . = LOAD_OFFSET;
> >         _start = .;
> > -       _stext = .;
> >         HEAD_TEXT_SECTION
> >         . = ALIGN(PAGE_SIZE);
> >
> >         __init_begin = .;
> >         INIT_TEXT_SECTION(PAGE_SIZE)
> > -       INIT_DATA_SECTION(16)
> >         . = ALIGN(8);
> >         __soc_early_init_table : {
> >                 __soc_early_init_table_start = .;
> > @@ -55,6 +53,7 @@ SECTIONS
> >         . = ALIGN(SECTION_ALIGN);
> >         .text : {
> >                 _text = .;
> > +               _stext = .;
> >                 TEXT_TEXT
> >                 SCHED_TEXT
> >                 CPUIDLE_TEXT
> > @@ -67,6 +66,8 @@ SECTIONS
> >                 _etext = .;
> >         }
> >
> > +       INIT_DATA_SECTION(16)
> > +
>
> I think you need to move EXIT_DATA as well. Currently, we have init
> data & text in one section.
It's not related to this issue. There is two check code problem:
 1.     static int static_obj(const void *obj)
    {
            unsigned long start = (unsigned long) &_stext,
                          end   = (unsigned long) &_end,
                          addr  = (unsigned long) obj;

            /*
             * static variable?
             */
            if ((addr >= start) && (addr < end))
                    return 1;

 2.     /* Is this address range in the kernel text area? */
    static inline void check_kernel_text_object(const unsigned long ptr,
                                                unsigned long n, bool to_user)
    {
            unsigned long textlow = (unsigned long)_stext;
            unsigned long texthigh = (unsigned long)_etext;
            unsigned long textlow_linear, texthigh_linear;

            if (overlaps(ptr, n, textlow, texthigh))
                    usercopy_abort("kernel text", NULL, to_user, ptr -
textlow, n);

The patch of commit: a0fa4027dc911 (riscv: Fixup static_obj() fail) broke 2th.

> In general it is better idea to separate those similar to ARM64.
> Additionally, ARM64 applies different mapping for init data & text
> as the init data section is marked as non-executable[1]
Yes, it's safer to protect init text & init data, but it's should be
another patch.

>
> However, we don't modify any permission for any init sections. Should
> we do that as well ?
Agree, we should do that.

>
> [1] https://patchwork.kernel.org/patch/9572869/
>
> >         /* Start of data section */
> >         _sdata = .;
> >         RO_DATA(SECTION_ALIGN)
> >
> > On Thu, Sep 24, 2020 at 3:36 PM Andreas Schwab <schwab@linux-m68k.org> wrote:
> > >
> > > On Sep 14 2020, Aurelien Jarno wrote:
> > >
> > > > How should we proceed to get that fixed in time for 5.9? For the older
> > > > branches where it has been backported (so far 5.7 and 5.8), should we
> > > > just get that commit reverted instead?
> > >
> > > Can this please be resolved ASAP?
> > >
> > > Andreas.
> > >
> > > --
> > > Andreas Schwab, schwab@linux-m68k.org
> > > GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
> > > "And now for something completely different."
> >
> >
> >
> > --
> > Best Regards
> >  Guo Ren
> >
> > ML: https://lore.kernel.org/linux-csky/
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
>
>
>
> --
> Regards,
> Atish

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/