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

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