kernel hangs after running program that uses a custom SIGSEGV handler

[Zong Li]

Alexandre Ghiti <alex at ghiti.fr> 於 2018年4月13日 週五 下午6:14寫道：

> Hi Stef,

> I'm happy to see there are solutions to this problem: I have a working
> port of hugetlb for riscv-linux and I was wondering how to support
> PROT_NONE.
> Can you share a link to the patches you mention please ?

> Thanks,

> Alex


> On 04/12/2018 02:14 AM, Stef O'Rear wrote:
> > On Wed, Apr 11, 2018 at 6:10 PM, Bruno Haible <bruno at clisp.org> wrote:
> >> Hi,
> >>
> >> $ uname
> >> Linux stage4.fedoraproject.org 4.16.0-rc2-00328-gebea62367bc4 #4 SMP
Mon Feb 26 16:05:16 GMT 2018 riscv64 riscv64 riscv64 GNU/Linux
> >>
> >> This kernel either hangs or prints "BUG" messages when running a
program that
> >> installs a SIGSEGV handler. That handler uses mprotect to change the
access
> >> permissions of memory pages. It is known to work fine on all other
Linux
> >> architectures that I tested.
> > The bug is caused by mishandling of PROT_NONE (failing to distinguish
> > between PROT_NONE and non-present pages), not by the segfault handler.
> > I sent a patch for this to Andrew and Richard a few weeks ago but
> > haven't had a chance to follow up.
> >
> > -s
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv


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Is there any update? I also encounter this issue, and I change the
permission like below.
Where is the patch as Stef O'Rear mention before?

diff --git a/arch/riscv/include/asm/pgtable.h
b/arch/riscv/include/asm/pgtable.h
index 16301966d65b..578f31510501 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -44,7 +44,7 @@
  /* Page protection bits */
  #define _PAGE_BASE     (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER)

-#define PAGE_NONE              __pgprot(0)
+#define PAGE_NONE              __pgprot(_PAGE_BASE)