Messages in this thread Patch in this message | | | Date | Sun, 30 Apr 2006 19:29:56 +0200 | From | blaisorblade@yahoo ... | Subject | [patch 03/14] remap_file_pages protection support: handle MANYPROTS VMAs |
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Val Henson <val.henson@intel.com>
Handle the possible existance of VM_MANYPROTS vmas, without actually creating them.
* Replace old uses of pgoff_to_pte with pgoff_prot_to_pte. * Introduce the flag, use it to read permissions from the PTE rather than from the VMA flags. * Replace the linear_page_index() check with save_nonlinear_pte(), which encapsulates the check. 2.6.14+ updates: * Add VM_MANYPROTS among cases needing copying of PTE at fork time rather than faulting. * check for VM_MANYPROTS in do_file_pte before complaining for pte_file PTE * check for VM_MANYPROTS in *_populate, when we skip installing pte_file PTE's for linear areas
Below there is a long explaination of why I've added VM_MANYPROTS, rather than simply overload VM_NONLINEAR. You can freely skip that if you have real work to do :-).
However, this patch is only sufficient if VM_MANYPROTS vmas are also marked as nonlinear. Otherwise also other changes are needed.
I've implemented both solutions - I've sent only full support for the easy case, but possibly I'll afterwards reintroduce the other changes; in particular, they're needed to make this useful for general usage beyond UML.
*) remap_file_pages protection support: add VM_MANYPROTS to fix existing usage of mprotect()
Distinguish between "normal" VMA and VMA with variable protection, by adding the VM_MANYPROTS flag. This is needed for various reasons:
* notify the arch fault handlers that they must not check VMA protection for giving SIGSEGV * fixing regression of mprotect() on !VM_MANYPROTS mappings (see below) * (in next patches) giving a sensible behaviour to mprotect on VM_MANYPROTS mappings * (TODO?) avoid regression in max file offset with r_f_p() for older mappings; we could use either the old offset encoding or the new offset-prot encoding depending on this flag. It's trivial to do, just I don't know whether existing apps will overflow the new limits. They go down from 2Tb to 1Tb on i386 and 512G on PPC, and from 256G to 128G on S390/31 bits. Give me a call in case. * (TODO?) on MAP_PRIVATE mappings, especially when they are readonly, we can easily support VM_MANYPROTS. This has been explicitly requested by Ulrich Drepper for DSO handling - creating a PROT_NONE VMA for guard pages is bad. And that is worse when you have a binary with 100 DSO, or a program with really many threads - Ulrich profiled a workload where the RB-tree lookup function is a performance bottleneck.
In fact, without this flag, we'd have indeed a regression with remap_file_pages VS mprotect, on uniform nonlinear VMAs.
mprotect alters the VMA prots and walks each present PTE, ignoring installed ones, even when pte_file() is on; their saved prots will be restored on faults, ignoring VMA ones and losing the mprotect() on them. So, in do_file_page(), we must restore anyway VMA prots when the VMA is uniform, as we used to do before this trail of patches.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Index: linux-2.6.git/include/linux/mm.h =================================================================== --- linux-2.6.git.orig/include/linux/mm.h +++ linux-2.6.git/include/linux/mm.h @@ -164,7 +164,14 @@ extern unsigned int kobjsize(const void #define VM_ACCOUNT 0x00100000 /* Is a VM accounted object */ #define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */ #define VM_NONLINEAR 0x00800000 /* Is non-linear (remap_file_pages) */ + +#ifndef CONFIG_MMU #define VM_MAPPED_COPY 0x01000000 /* T if mapped copy of data (nommu mmap) */ +#else +#define VM_MANYPROTS 0x01000000 /* The VM individual pages have + different protections + (remap_file_pages)*/ +#endif #define VM_INSERTPAGE 0x02000000 /* The vma has had "vm_insert_page()" done on it */ #ifndef VM_STACK_DEFAULT_FLAGS /* arch can override this */ Index: linux-2.6.git/include/linux/pagemap.h =================================================================== --- linux-2.6.git.orig/include/linux/pagemap.h +++ linux-2.6.git/include/linux/pagemap.h @@ -165,6 +165,28 @@ static inline pgoff_t linear_page_index( return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT); } +/*** + * Checks if the PTE is nonlinear, and if yes sets it. + * @vma: the VMA in which @addr is; we don't check if it's VM_NONLINEAR, just + * if this PTE is nonlinear. + * @addr: the addr which @pte refers to. + * @pte: the old PTE value (to read its protections. + * @ptep: the PTE pointer (for setting it). + * @mm: passed to set_pte_at. + * @page: the page which was installed (to read its ->index, i.e. the old + * offset inside the file. + */ +static inline void save_nonlinear_pte(pte_t pte, pte_t * ptep, struct + vm_area_struct *vma, struct mm_struct *mm, struct page* page, + unsigned long addr) +{ + pgprot_t pgprot = pte_to_pgprot(pte); + if (linear_page_index(vma, addr) != page->index || + pgprot_val(pgprot) != pgprot_val(vma->vm_page_prot)) + set_pte_at(mm, addr, ptep, pgoff_prot_to_pte(page->index, + pgprot)); +} + extern void FASTCALL(__lock_page(struct page *page)); extern void FASTCALL(unlock_page(struct page *page)); Index: linux-2.6.git/mm/fremap.c =================================================================== --- linux-2.6.git.orig/mm/fremap.c +++ linux-2.6.git/mm/fremap.c @@ -49,7 +49,7 @@ static int zap_pte(struct mm_struct *mm, * previously existing mapping. */ int install_page(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long addr, struct page *page, pgprot_t prot) + unsigned long addr, struct page *page, pgprot_t pgprot) { struct inode *inode; pgoff_t size; @@ -79,7 +79,7 @@ int install_page(struct mm_struct *mm, s inc_mm_counter(mm, file_rss); flush_icache_page(vma, page); - set_pte_at(mm, addr, pte, mk_pte(page, prot)); + set_pte_at(mm, addr, pte, mk_pte(page, pgprot)); page_add_file_rmap(page); pte_val = *pte; update_mmu_cache(vma, addr, pte_val); @@ -96,7 +96,7 @@ EXPORT_SYMBOL(install_page); * previously existing mapping. */ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long addr, unsigned long pgoff, pgprot_t prot) + unsigned long addr, unsigned long pgoff, pgprot_t pgprot) { int err = -ENOMEM; pte_t *pte; @@ -112,7 +112,7 @@ int install_file_pte(struct mm_struct *m dec_mm_counter(mm, file_rss); } - set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); + set_pte_at(mm, addr, pte, pgoff_prot_to_pte(pgoff, pgprot)); pte_val = *pte; update_mmu_cache(vma, addr, pte_val); pte_unmap_unlock(pte, ptl); Index: linux-2.6.git/mm/memory.c =================================================================== --- linux-2.6.git.orig/mm/memory.c +++ linux-2.6.git/mm/memory.c @@ -581,7 +581,8 @@ int copy_page_range(struct mm_struct *ds * readonly mappings. The tradeoff is that copy_page_range is more * efficient than faulting. */ - if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) { + if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_MANYPROTS| + VM_PFNMAP|VM_INSERTPAGE))) { if (!vma->anon_vma) return 0; } @@ -650,11 +651,11 @@ static unsigned long zap_pte_range(struc tlb_remove_tlb_entry(tlb, pte, addr); if (unlikely(!page)) continue; - if (unlikely(details) && details->nonlinear_vma - && linear_page_index(details->nonlinear_vma, - addr) != page->index) - set_pte_at(mm, addr, pte, - pgoff_to_pte(page->index)); + if (unlikely(details) && details->nonlinear_vma) { + save_nonlinear_pte(ptent, pte, + details->nonlinear_vma, + mm, page, addr); + } if (PageAnon(page)) anon_rss--; else { @@ -2159,12 +2160,13 @@ static int do_file_page(struct mm_struct int write_access, pte_t orig_pte) { pgoff_t pgoff; + pgprot_t pgprot; int err; if (!pte_unmap_same(mm, pmd, page_table, orig_pte)) return VM_FAULT_MINOR; - if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) { + if (unlikely(!(vma->vm_flags & (VM_NONLINEAR|VM_MANYPROTS)))) { /* * Page table corrupted: show pte and kill process. */ @@ -2174,8 +2176,11 @@ static int do_file_page(struct mm_struct /* We can then assume vm->vm_ops && vma->vm_ops->populate */ pgoff = pte_to_pgoff(orig_pte); + pgprot = (vma->vm_flags & VM_MANYPROTS) ? pte_to_pgprot(orig_pte) : + vma->vm_page_prot; + err = vma->vm_ops->populate(vma, address & PAGE_MASK, PAGE_SIZE, - vma->vm_page_prot, pgoff, 0); + pgprot, pgoff, 0); if (err == -ENOMEM) return VM_FAULT_OOM; if (err) Index: linux-2.6.git/mm/rmap.c =================================================================== --- linux-2.6.git.orig/mm/rmap.c +++ linux-2.6.git/mm/rmap.c @@ -721,8 +721,7 @@ static void try_to_unmap_cluster(unsigne pteval = ptep_clear_flush(vma, address, pte); /* If nonlinear, store the file page offset in the pte. */ - if (page->index != linear_page_index(vma, address)) - set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); + save_nonlinear_pte(pteval, pte, vma, mm, page, address); /* Move the dirty bit to the physical page now the pte is gone. */ if (pte_dirty(pteval)) Index: linux-2.6.git/mm/filemap.c =================================================================== --- linux-2.6.git.orig/mm/filemap.c +++ linux-2.6.git/mm/filemap.c @@ -1587,7 +1587,7 @@ repeat: page_cache_release(page); return err; } - } else if (vma->vm_flags & VM_NONLINEAR) { + } else if (vma->vm_flags & (VM_NONLINEAR|VM_MANYPROTS)) { /* No page was found just because we can't read it in now (being * here implies nonblock != 0), but the page may exist, so set * the PTE to fault it in later. */ Index: linux-2.6.git/mm/shmem.c =================================================================== --- linux-2.6.git.orig/mm/shmem.c +++ linux-2.6.git/mm/shmem.c @@ -1275,7 +1275,7 @@ static int shmem_populate(struct vm_area page_cache_release(page); return err; } - } else if (vma->vm_flags & VM_NONLINEAR) { + } else if (vma->vm_flags & (VM_NONLINEAR|VM_MANYPROTS)) { /* No page was found just because we can't read it in * now (being here implies nonblock != 0), but the page * may exist, so set the PTE to fault it in later. */ -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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