linux-kernel - Re: [PATCH v3 2/2] riscv: Cleanup KASAN

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Message-ID: <CAMuHMdXdhTUKuvJkJGUm=ESpwA6R06eKV5q6wFOJftJ1p3R7nw@mail.gmail.com>
Date:   Tue, 30 Mar 2021 11:47:30 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     alex@...ti.fr, Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>, nylon7@...estech.com,
        Nick Hu <nickhu@...estech.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 2/2] riscv: Cleanup KASAN_VMALLOC support

Hi Palmer,

On Tue, Mar 30, 2021 at 7:08 AM Palmer Dabbelt <palmer@...belt.com> wrote:
> On Sat, 13 Mar 2021 00:45:05 PST (-0800), alex@...ti.fr wrote:
> > When KASAN vmalloc region is populated, there is no userspace process and
> > the page table in use is swapper_pg_dir, so there is no need to read
> > SATP. Then we can use the same scheme used by kasan_populate_p*d
> > functions to go through the page table, which harmonizes the code.
> >
> > In addition, make use of set_pgd that goes through all unused page table
> > levels, contrary to p*d_populate functions, which makes this function work
> > whatever the number of page table levels.
> >
> > Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
> > Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> > ---
> >  arch/riscv/mm/kasan_init.c | 59 ++++++++++++--------------------------
> >  1 file changed, 18 insertions(+), 41 deletions(-)
> >
> > diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> > index 57bf4ae09361..c16178918239 100644
> > --- a/arch/riscv/mm/kasan_init.c
> > +++ b/arch/riscv/mm/kasan_init.c
> > @@ -11,18 +11,6 @@
> >  #include <asm/fixmap.h>
> >  #include <asm/pgalloc.h>
> >
> > -static __init void *early_alloc(size_t size, int node)
> > -{
> > -     void *ptr = memblock_alloc_try_nid(size, size,
> > -             __pa(MAX_DMA_ADDRESS), MEMBLOCK_ALLOC_ACCESSIBLE, node);
> > -
> > -     if (!ptr)
> > -             panic("%pS: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
> > -                     __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
> > -
> > -     return ptr;
> > -}
> > -
> >  extern pgd_t early_pg_dir[PTRS_PER_PGD];
> >  asmlinkage void __init kasan_early_init(void)
> >  {
> > @@ -155,38 +143,27 @@ static void __init kasan_populate(void *start, void *end)
> >       memset(start, KASAN_SHADOW_INIT, end - start);
> >  }
> >
> > -void __init kasan_shallow_populate(void *start, void *end)
> > +static void __init kasan_shallow_populate_pgd(unsigned long vaddr, unsigned long end)
> >  {
> > -     unsigned long vaddr = (unsigned long)start & PAGE_MASK;
> > -     unsigned long vend = PAGE_ALIGN((unsigned long)end);
> > -     unsigned long pfn;
> > -     int index;
> > +     unsigned long next;
> >       void *p;
> > -     pud_t *pud_dir, *pud_k;
> > -     pgd_t *pgd_dir, *pgd_k;
> > -     p4d_t *p4d_dir, *p4d_k;
> > -
> > -     while (vaddr < vend) {
> > -             index = pgd_index(vaddr);
> > -             pfn = csr_read(CSR_SATP) & SATP_PPN;
> > -             pgd_dir = (pgd_t *)pfn_to_virt(pfn) + index;
> > -             pgd_k = init_mm.pgd + index;
> > -             pgd_dir = pgd_offset_k(vaddr);
> > -             set_pgd(pgd_dir, *pgd_k);
> > -
> > -             p4d_dir = p4d_offset(pgd_dir, vaddr);
> > -             p4d_k  = p4d_offset(pgd_k, vaddr);
> > -
> > -             vaddr = (vaddr + PUD_SIZE) & PUD_MASK;
> > -             pud_dir = pud_offset(p4d_dir, vaddr);
> > -             pud_k = pud_offset(p4d_k, vaddr);
> > -
> > -             if (pud_present(*pud_dir)) {
> > -                     p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
> > -                     pud_populate(&init_mm, pud_dir, p);
> > +     pgd_t *pgd_k = pgd_offset_k(vaddr);
> > +
> > +     do {
> > +             next = pgd_addr_end(vaddr, end);
> > +             if (pgd_page_vaddr(*pgd_k) == (unsigned long)lm_alias(kasan_early_shadow_pmd)) {
> > +                     p = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> > +                     set_pgd(pgd_k, pfn_pgd(PFN_DOWN(__pa(p)), PAGE_TABLE));
> >               }
> > -             vaddr += PAGE_SIZE;
> > -     }
> > +     } while (pgd_k++, vaddr = next, vaddr != end);
> > +}
> > +
> > +static void __init kasan_shallow_populate(void *start, void *end)
> > +{
> > +     unsigned long vaddr = (unsigned long)start & PAGE_MASK;
> > +     unsigned long vend = PAGE_ALIGN((unsigned long)end);
> > +
> > +     kasan_shallow_populate_pgd(vaddr, vend);
> >
> >       local_flush_tlb_all();
> >  }
>
> Thanks, this is on for-next.

Your for-next does not include your fixes branch, hence they now conflict,
and for-next lacks the local_flush_tlb_all().

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds