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Date: Wed, 22 Jul 2015 17:25:08 +0300
From: Alexey Klimov <klimov.linux@...il.com>
To: Andrey Ryabinin <a.ryabinin@...sung.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
linux-arm-kernel@...ts.infradead.org,
Arnd Bergmann <arnd@...db.de>, linux-mm@...ck.org,
Linus Walleij <linus.walleij@...aro.org>, x86@...nel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
David Keitel <dkeitel@...eaurora.org>,
Ingo Molnar <mingo@...hat.com>,
Alexander Potapenko <glider@...gle.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Dmitry Vyukov <dvyukov@...gle.com>,
Yury Norov <yury.norov@...il.com>
Subject: Re: [PATCH v3 1/5] mm: kasan: introduce generic kasan_populate_zero_shadow()
Hi Andrey,
Could you please check minor comments below?
On Wed, Jul 22, 2015 at 1:30 PM, Andrey Ryabinin <a.ryabinin@...sung.com> wrote:
> Introduce generic kasan_populate_zero_shadow(start, end).
> This function maps kasan_zero_page to the [start, end] addresses.
>
> In follow on patches it will be used for ARMv8 (and maybe other
> architectures) and will replace x86_64 specific populate_zero_shadow().
>
> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
> ---
> arch/x86/mm/kasan_init_64.c | 8 +--
> include/linux/kasan.h | 8 +++
> mm/kasan/Makefile | 2 +-
> mm/kasan/kasan_init.c | 142 ++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 155 insertions(+), 5 deletions(-)
> create mode 100644 mm/kasan/kasan_init.c
>
[..]
> diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
> new file mode 100644
> index 0000000..37fb46a
> --- /dev/null
> +++ b/mm/kasan/kasan_init.c
> @@ -0,0 +1,142 @@
> +#include <linux/bootmem.h>
> +#include <linux/init.h>
> +#include <linux/kasan.h>
> +#include <linux/kernel.h>
> +#include <linux/memblock.h>
> +#include <linux/pfn.h>
> +
> +#include <asm/page.h>
> +#include <asm/pgalloc.h>
> +
Are you releasing code under GPL?
Shouldn't there be any license header in such new file?
> +static __init void *early_alloc(size_t size, int node)
> +{
> + return memblock_virt_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
> + BOOTMEM_ALLOC_ACCESSIBLE, node);
> +}
> +
> +static int __init zero_pte_populate(pmd_t *pmd, unsigned long addr,
> + unsigned long end)
> +{
> + pte_t *pte = pte_offset_kernel(pmd, addr);
> + pte_t zero_pte;
> +
> + zero_pte = pfn_pte(PFN_DOWN(__pa(kasan_zero_page)), PAGE_KERNEL);
> + zero_pte = pte_wrprotect(zero_pte);
> +
> + while (addr + PAGE_SIZE <= end) {
> + set_pte_at(&init_mm, addr, pte, zero_pte);
> + addr += PAGE_SIZE;
> + pte = pte_offset_kernel(pmd, addr);
> + }
> + return 0;
> +}
> +
> +static int __init zero_pmd_populate(pud_t *pud, unsigned long addr,
> + unsigned long end)
> +{
> + int ret = 0;
> + pmd_t *pmd = pmd_offset(pud, addr);
> + unsigned long next;
> +
> + do {
> + next = pmd_addr_end(addr, end);
> +
> + if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
> + pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
> + continue;
> + }
> +
> + if (pmd_none(*pmd)) {
> + void *p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
> + if (!p)
> + return -ENOMEM;
> + pmd_populate_kernel(&init_mm, pmd, p);
> + }
> + zero_pte_populate(pmd, addr, pmd_addr_end(addr, end));
> + } while (pmd++, addr = next, addr != end);
> +
> + return ret;
In zero_{pgd, pud, pmd}_populate you're not resetting ret variable
used as return value inside function so maybe you don't need ret
variable at all. What about return 0 in the end and -ENOMEM in error
case?
> +}
> +
> +static int __init zero_pud_populate(pgd_t *pgd, unsigned long addr,
> + unsigned long end)
> +{
> + int ret = 0;
> + pud_t *pud = pud_offset(pgd, addr);
> + unsigned long next;
> +
> + do {
> + next = pud_addr_end(addr, end);
> + if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
> + pmd_t *pmd;
> +
> + pud_populate(&init_mm, pud, kasan_zero_pmd);
> + pmd = pmd_offset(pud, addr);
> + pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
> + continue;
> + }
> +
> + if (pud_none(*pud)) {
> + void *p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
> + if (!p)
> + return -ENOMEM;
> + pud_populate(&init_mm, pud, p);
> + }
> + zero_pmd_populate(pud, addr, pud_addr_end(addr, end));
> + } while (pud++, addr = next, addr != end);
> +
> + return ret;
> +}
> +
> +static int __init zero_pgd_populate(unsigned long addr, unsigned long end)
> +{
> + int ret = 0;
> + pgd_t *pgd = pgd_offset_k(addr);
> + unsigned long next;
> +
> + do {
> + next = pgd_addr_end(addr, end);
> +
> + if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
> + pud_t *pud;
> + pmd_t *pmd;
> +
> + /*
> + * kasan_zero_pud should be populated with pmds
> + * at this moment.
> + * [pud,pmd]_populate*() bellow needed only for
> + * 3,2 - level page tables where we don't have
> + * puds,pmds, so pgd_populate(), pud_populate()
> + * is noops.
> + */
> + pgd_populate(&init_mm, pgd, kasan_zero_pud);
> + pud = pud_offset(pgd, addr);
> + pud_populate(&init_mm, pud, kasan_zero_pmd);
> + pmd = pmd_offset(pud, addr);
> + pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
> + continue;
> + }
> +
> + if (pgd_none(*pgd)) {
> + void *p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
> + if (!p)
> + return -ENOMEM;
> + pgd_populate(&init_mm, pgd, p);
> + }
> + zero_pud_populate(pgd, addr, next);
But you're not checking return value after zero_pud_populate() and
zero_pmd_populate() that might fail with ENOMEM.
Is it critical here on init or can they be converted to return void?
> +/**
> + * kasan_populate_zero_shadow - populate shadow memory region with
> + * kasan_zero_page
> + * @start - start of the memory range to populate
> + * @end - end of the memory range to populate
> + */
> +void __init kasan_populate_zero_shadow(const void *start, const void *end)
> +{
> + if (zero_pgd_populate((unsigned long)start, (unsigned long)end))
> + panic("kasan: unable to map zero shadow!");
> +}
> --
> 2.4.5
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
--
Best regards, Klimov Alexey
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