From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo 'Blaisorblade' Giarrusso Subject: [PATCH 03/11] RFP prot support: handle MANYPROTS VMAs Date: Sat, 31 Mar 2007 02:35:25 +0200 Message-ID: <20070331003524.3415.94582.stgit@americanbeauty.home.lan> In-Reply-To: <20070331003453.3415.70825.stgit@americanbeauty.home.lan> References: <20070331003453.3415.70825.stgit@americanbeauty.home.lan> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: mingo@redhat.com, linux-mm@kvack.org, Jeff Dike , Paolo 'Blaisorblade' Giarrusso List-ID: 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 * (theoretical, rejected) 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. However this was rejected by a comment in an earlier iteration of this patch, because such applications should have moved to 64bit anyway. * (possible feature) 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 --- include/linux/mm.h | 7 +++++++ include/linux/pagemap.h | 22 ++++++++++++++++++++++ mm/fremap.c | 4 ++-- mm/memory.c | 41 +++++++++++++++++++++++++++++------------ mm/rmap.c | 3 +-- 5 files changed, 61 insertions(+), 16 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index bcea993..1959d9b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -168,7 +168,14 @@ extern int do_mprotect(unsigned long start, size_t len, unsigned long prot); #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 */ #define VM_ALWAYSDUMP 0x04000000 /* Always include in core dumps */ diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 10b96cc..acd10e8 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -155,6 +155,28 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma, 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(__lock_page_nosync(struct page *page)); extern void FASTCALL(unlock_page(struct page *page)); diff --git a/mm/fremap.c b/mm/fremap.c index 5f50d73..f571674 100644 --- a/mm/fremap.c +++ b/mm/fremap.c @@ -51,7 +51,7 @@ static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, * previously existing mapping. */ static 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; @@ -64,7 +64,7 @@ static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, if (!pte_none(*pte)) zap_pte(mm, vma, addr, pte); - set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); + set_pte_at(mm, addr, pte, pgoff_prot_to_pte(pgoff, pgprot)); /* * We don't need to run update_mmu_cache() here because the "file pte" * being installed by install_file_pte() is not a real pte - it's a diff --git a/mm/memory.c b/mm/memory.c index 57559a5..577b8bc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -597,7 +597,8 @@ int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm, * 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; } @@ -667,11 +668,11 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, 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 { @@ -2213,10 +2214,14 @@ oom: * We enter with non-exclusive mmap_sem (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. * We return with mmap_sem still held, but pte unmapped and unlocked. + * + * __do_fault_pgprot allows specifying also page protection for VM_MANYPROTS + * vmas. */ -static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma, +static int __do_fault_pgprot(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pte_t *page_table, pmd_t *pmd, - pgoff_t pgoff, unsigned int flags, pte_t orig_pte) + pgoff_t pgoff, pgprot_t pgprot, unsigned int flags, + pte_t orig_pte) { spinlock_t *ptl; struct page *page, *faulted_page; @@ -2307,7 +2312,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma, /* Only go through if we didn't race with anybody else... */ if (likely(pte_same(*page_table, orig_pte))) { flush_icache_page(vma, page); - entry = mk_pte(page, vma->vm_page_prot); + entry = mk_pte(page, pgprot); if (flags & FAULT_FLAG_WRITE) entry = maybe_mkwrite(pte_mkdirty(entry), vma); set_pte_at(mm, address, page_table, entry); @@ -2348,6 +2353,15 @@ out: return fdata.type; } +static inline int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + pgoff_t pgoff, unsigned int flags, pte_t orig_pte) +{ + return __do_fault_pgprot(mm, vma, address, page_table, pmd, pgoff, + vma->vm_page_prot, flags, orig_pte); + +} + static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pte_t *page_table, pmd_t *pmd, int write_access, pte_t orig_pte) @@ -2377,11 +2391,12 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned int flags = FAULT_FLAG_NONLINEAR | (write_access ? FAULT_FLAG_WRITE : 0); pgoff_t pgoff; + pgprot_t pgprot; 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)) || !(vma->vm_flags & VM_CAN_NONLINEAR))) { /* * Page table corrupted: show pte and kill process. @@ -2391,9 +2406,11 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma, } pgoff = pte_to_pgoff(orig_pte); + pgprot = (vma->vm_flags & VM_MANYPROTS) ? pte_file_to_pgprot(orig_pte) : + vma->vm_page_prot; - return __do_fault(mm, vma, address, page_table, pmd, pgoff, - flags, orig_pte); + return __do_fault_pgprot(mm, vma, address, page_table, pmd, pgoff, + pgprot, flags, orig_pte); } /* diff --git a/mm/rmap.c b/mm/rmap.c index 31d758d..63cd875 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -831,8 +831,7 @@ static void try_to_unmap_cluster(unsigned long cursor, 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)) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org