Re: [External] Re: [PATCH v2] riscv/mm/fault: add show_pte() before die()

[yunhui cui]

Hi drew,

On Tue, Jul 23, 2024 at 12:56 AM Andrew Jones <ajones@xxxxxxxxxxxxxxxx> wrote:
>
> On Mon, Jul 22, 2024 at 12:20:37PM 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@xxxxxxxxxxxxx>
> > Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> > ---
> >  arch/riscv/mm/fault.c | 53 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >
> > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> > index 5224f3733802..666d282a8bf4 100644
> > --- a/arch/riscv/mm/fault.c
> > +++ b/arch/riscv/mm/fault.c
> > @@ -22,6 +22,58 @@
> >
> >  #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;
> > +
> > +     pr_alert("Current %s pgtable: %luK pagesize, %d-bit VAs, pgdp=0x%016lx\n",
> > +              current->comm, PAGE_SIZE/SZ_1K, VA_BITS,
> > +              (mm == &init_mm ? __pa_symbol(mm->pgd) :
> > +              (unsigned long)virt_to_phys(mm->pgd)));
>
> nit: unnecessary () around the ternary.
Okay, I'll update it in v3.

>
> > +
> > +     pgdp = pgd_offset(mm, addr);
> > +     pgd = pgdp_get(pgdp);
> > +     pr_alert("[%016lx] pgd=%016lx", addr, pgd_val(pgd));
> > +     if (pgd_none(pgd) || pgd_bad(pgd) || pgd_leaf(pgd))
> > +             goto out;
> > +
> > +     p4dp = p4d_offset(pgdp, addr);
> > +     p4d = p4dp_get(p4dp);
> > +     pr_cont(", p4d=%016lx", p4d_val(p4d));
> > +     if (p4d_none(p4d) || p4d_bad(p4d) || p4d_leaf(p4d))
> > +             goto out;
> > +
> > +     pudp = pud_offset(p4dp, addr);
> > +     pud = pudp_get(pudp);
> > +     pr_cont(", pud=%016lx", pud_val(pud));
> > +     if (pud_none(pud) || pud_bad(pud) || pud_leaf(pud))
> > +             goto out;
> > +
> > +     pmdp = pmd_offset(pudp, addr);
> > +     pmd = pmdp_get(pmdp);
> > +     pr_cont(", pmd=%016lx", pmd_val(pmd));
> > +     if (pmd_none(pmd) || pmd_bad(pmd) || pmd_leaf(pmd))
> > +             goto out;
> > +
> > +     ptep = pte_offset_map(pmdp, addr);
> > +     if (!ptep)
> > +             goto out;
> > +
> > +     pte = ptep_get(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 +83,7 @@ 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
> >
> >
>
> Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
>
> Thanks,
> drew

Thanks,
Yunhui