[External] Re: [PATCH] riscv/mm/fault: add show_pte() before die()

[yunhui cui]

Hi drew,

On Fri, Jul 19, 2024 at 10:33 PM Andrew Jones <ajones at ventanamicro.com> wrote:
>
> On Thu, Jul 18, 2024 at 10:09:35AM GMT, Yunhui Cui wrote:
> > When the kernel displays "Unable to handle kernel paging request at
> > virtual address", we would like to confirm the status of the virtual
> > address in the page table. So add show_pte() before die().
> >
> > Signed-off-by: Yunhui Cui <cuiyunhui at bytedance.com>
> > ---
> >  arch/riscv/mm/fault.c | 47 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 47 insertions(+)
> >
> > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> > index 90d4ba36d1d0..dfe3ce38e16b 100644
> > --- a/arch/riscv/mm/fault.c
> > +++ b/arch/riscv/mm/fault.c
> > @@ -22,6 +22,52 @@
> >
> >  #include "../kernel/head.h"
> >
> > +static void show_pte(unsigned long addr)
> > +{
> > +     pgd_t *pgdp, pgd;
> > +     p4d_t *p4dp, p4d;
> > +     pud_t *pudp, pud;
> > +     pmd_t *pmdp, pmd;
> > +     pte_t *ptep, pte;
> > +     struct mm_struct *mm = current->mm;
> > +
> > +     if (!mm)
> > +             mm = &init_mm;
>
> arm64 show_pte starts with a summary line where the pgtable type (swapper
> vs. user), number of VA bits, and physical address of the pgd are
> displayed. Should we add that too?
Oaky， I will add it in v2.

>
> Thanks,
> drew
>
> > +     pgdp = pgd_offset(mm, addr);
> > +     pgd = READ_ONCE(*pgdp);
> > +     pr_alert("[%016lx] pgd=%016lx", addr, pgd_val(pgd));
> > +     if (pgd_none(pgd) || pgd_bad(pgd))
> > +             goto out;
> > +
> > +     p4dp = p4d_offset(pgdp, addr);
> > +     p4d = READ_ONCE(*p4dp);
> > +     pr_cont(", p4d=%016lx", p4d_val(p4d));
> > +     if (p4d_none(p4d) || p4d_bad(p4d))
> > +             goto out;
> > +
> > +     pudp = pud_offset(p4dp, addr);
> > +     pud = READ_ONCE(*pudp);
> > +     pr_cont(", pud=%016lx", pud_val(pud));
> > +     if (pud_none(pud) || pud_bad(pud))
> > +             goto out;
> > +
> > +     pmdp = pmd_offset(pudp, addr);
> > +     pmd = READ_ONCE(*pmdp);
> > +     pr_cont(", pmd=%016lx", pmd_val(pmd));
> > +     if (pmd_none(pmd) || pmd_bad(pmd))
> > +             goto out;
> > +
> > +     ptep = pte_offset_map(pmdp, addr);
> > +     if (!ptep)
> > +             goto out;
> > +
> > +     pte = READ_ONCE(*ptep);
> > +     pr_cont(", pte=%016lx", pte_val(pte));
> > +     pte_unmap(ptep);
> > +out:
> > +     pr_cont("\n");
> > +}
> > +
> >  static void die_kernel_fault(const char *msg, unsigned long addr,
> >               struct pt_regs *regs)
> >  {
> > @@ -31,6 +77,7 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
> >               addr);
> >
> >       bust_spinlocks(0);
> > +     show_pte(addr);
> >       die(regs, "Oops");
> >       make_task_dead(SIGKILL);
> >  }
> > --
> > 2.39.2
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

Thanks，
Yunhui