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Message-ID: <e6651703-000b-6238-d853-d282daebba0f@c-s.fr>
Date: Wed, 1 Apr 2020 07:50:53 +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 01/04/2020 à 04:27, Russell Currey a écrit :
> On Tue, 2020-03-31 at 11:56 +0200, Christophe Leroy wrote:
>>
>> 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
>
> OK cool, so I can just drop that hunk? Will try that and make sure it
> rebases on powerpc/next
Well, you still have to remove __change_page_attr_noflush() and
change_page_attr(), everything else in this patch should still be the same.
Christophe
>
> - Russell
>
>>
>>
>>> -{
>>> - 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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