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Date: Tue, 31 Mar 2020 11:56:22 +0200
From: Christophe Leroy <christophe.leroy@....fr>
To: Russell Currey <ruscur@...sell.cc>, linuxppc-dev@...ts.ozlabs.org
Cc: mpe@...erman.id.au, ajd@...ux.ibm.com, dja@...ens.net, npiggin@...il.com,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v7 7/7] powerpc/32: use set_memory_attr()
Le 31/03/2020 à 06:48, Russell Currey a écrit :
> From: Christophe Leroy <christophe.leroy@....fr>
>
> Use set_memory_attr() instead of the PPC32 specific change_page_attr()
>
> change_page_attr() was checking that the address was not mapped by
> blocks and was handling highmem, but that's unneeded because the
> affected pages can't be in highmem and block mapping verification
> is already done by the callers.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
> arch/powerpc/mm/pgtable_32.c | 95 ++++--------------------------------
> 1 file changed, 10 insertions(+), 85 deletions(-)
>
> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index 5fb90edd865e..3d92eaf3ee2f 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -23,6 +23,7 @@
> #include <linux/highmem.h>
> #include <linux/memblock.h>
> #include <linux/slab.h>
> +#include <linux/set_memory.h>
>
> #include <asm/pgtable.h>
> #include <asm/pgalloc.h>
> @@ -121,99 +122,20 @@ void __init mapin_ram(void)
> }
> }
>
> -/* Scan the real Linux page tables and return a PTE pointer for
> - * a virtual address in a context.
> - * Returns true (1) if PTE was found, zero otherwise. The pointer to
> - * the PTE pointer is unmodified if PTE is not found.
> - */
> -static int
> -get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
This will conflict, get_pteptr() is gone now, see
https://github.com/linuxppc/linux/commit/2efc7c085f05870eda6f29ac71eeb83f3bd54415
Christophe
> -{
> - pgd_t *pgd;
> - pud_t *pud;
> - pmd_t *pmd;
> - pte_t *pte;
> - int retval = 0;
> -
> - pgd = pgd_offset(mm, addr & PAGE_MASK);
> - if (pgd) {
> - pud = pud_offset(pgd, addr & PAGE_MASK);
> - if (pud && pud_present(*pud)) {
> - pmd = pmd_offset(pud, addr & PAGE_MASK);
> - if (pmd_present(*pmd)) {
> - pte = pte_offset_map(pmd, addr & PAGE_MASK);
> - if (pte) {
> - retval = 1;
> - *ptep = pte;
> - if (pmdp)
> - *pmdp = pmd;
> - /* XXX caller needs to do pte_unmap, yuck */
> - }
> - }
> - }
> - }
> - return(retval);
> -}
> -
> -static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
> -{
> - pte_t *kpte;
> - pmd_t *kpmd;
> - unsigned long address;
> -
> - BUG_ON(PageHighMem(page));
> - address = (unsigned long)page_address(page);
> -
> - if (v_block_mapped(address))
> - return 0;
> - if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
> - return -EINVAL;
> - __set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
> - pte_unmap(kpte);
> -
> - return 0;
> -}
> -
> -/*
> - * Change the page attributes of an page in the linear mapping.
> - *
> - * THIS DOES NOTHING WITH BAT MAPPINGS, DEBUG USE ONLY
> - */
> -static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
> -{
> - int i, err = 0;
> - unsigned long flags;
> - struct page *start = page;
> -
> - local_irq_save(flags);
> - for (i = 0; i < numpages; i++, page++) {
> - err = __change_page_attr_noflush(page, prot);
> - if (err)
> - break;
> - }
> - wmb();
> - local_irq_restore(flags);
> - flush_tlb_kernel_range((unsigned long)page_address(start),
> - (unsigned long)page_address(page));
> - return err;
> -}
> -
> void mark_initmem_nx(void)
> {
> - struct page *page = virt_to_page(_sinittext);
> unsigned long numpages = PFN_UP((unsigned long)_einittext) -
> PFN_DOWN((unsigned long)_sinittext);
>
> if (v_block_mapped((unsigned long)_stext + 1))
> mmu_mark_initmem_nx();
> else
> - change_page_attr(page, numpages, PAGE_KERNEL);
> + set_memory_attr((unsigned long)_sinittext, numpages, PAGE_KERNEL);
> }
>
> #ifdef CONFIG_STRICT_KERNEL_RWX
> void mark_rodata_ro(void)
> {
> - struct page *page;
> unsigned long numpages;
>
> if (v_block_mapped((unsigned long)_sinittext)) {
> @@ -222,20 +144,18 @@ void mark_rodata_ro(void)
> return;
> }
>
> - page = virt_to_page(_stext);
> numpages = PFN_UP((unsigned long)_etext) -
> PFN_DOWN((unsigned long)_stext);
>
> - change_page_attr(page, numpages, PAGE_KERNEL_ROX);
> + set_memory_attr((unsigned long)_stext, numpages, PAGE_KERNEL_ROX);
> /*
> * mark .rodata as read only. Use __init_begin rather than __end_rodata
> * to cover NOTES and EXCEPTION_TABLE.
> */
> - page = virt_to_page(__start_rodata);
> numpages = PFN_UP((unsigned long)__init_begin) -
> PFN_DOWN((unsigned long)__start_rodata);
>
> - change_page_attr(page, numpages, PAGE_KERNEL_RO);
> + set_memory_attr((unsigned long)__start_rodata, numpages, PAGE_KERNEL_RO);
>
> // mark_initmem_nx() should have already run by now
> ptdump_check_wx();
> @@ -245,9 +165,14 @@ void mark_rodata_ro(void)
> #ifdef CONFIG_DEBUG_PAGEALLOC
> void __kernel_map_pages(struct page *page, int numpages, int enable)
> {
> + unsigned long addr = (unsigned long)page_address(page);
> +
> if (PageHighMem(page))
> return;
>
> - change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
> + if (enable)
> + set_memory_attr(addr, numpages, PAGE_KERNEL);
> + else
> + set_memory_attr(addr, numpages, __pgprot(0));
> }
> #endif /* CONFIG_DEBUG_PAGEALLOC */
>
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