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Message-ID: <mhng-93309746-0fd6-42ec-b574-bf1ce486f34a@palmerdabbelt-glaptop>
Date: Wed, 14 Apr 2021 23:16:24 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: geert@...ux-m68k.org
CC: alex@...ti.fr, Paul Walmsley <paul.walmsley@...ive.com>,
aou@...s.berkeley.edu, nylon7@...estech.com, nickhu@...estech.com,
aryabinin@...tuozzo.com, glider@...gle.com, dvyukov@...gle.com,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 2/2] riscv: Cleanup KASAN_VMALLOC support
On Tue, 30 Mar 2021 02:47:30 PDT (-0700), geert@...ux-m68k.org wrote:
> 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().
This came up before and I don't think we ever sorted out what the right
thing to do is. Right now I'm keeping for-next pinned an at early RC,
but fast-forwarding fixes to the latest RC every time I sent a PR. I
don't have fixes merged back into for-next because I don't want those
merges to show up when I send my merge window PRs.
For this one I purposefully left out the local_flush_tlb_all() whene I
pulled in this patch, and was planning on fixing it up along with any
other merge conflicts when I send along the PR. It does all seem like a
bit of a song and dance here, though, so I'm open to suggestions as to
how to run this better -- though last time I went through that exercise
it seemed like everyone had their own way of doing it, they all had a
different set of issues, and I was at least familiar with this flavor of
craziness.
I was kind of tempted to convert for-next over into a branch that only
contains merges, though, which would make it a bit easier to merge fixes
in.
>
> Gr{oetje,eeting}s,
>
> Geert
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