patch-2.4.20 linux-2.4.20/arch/i386/mm/pageattr.c

• Lines: 176
• Date: Thu Nov 28 15:53:09 2002
• Orig file: linux-2.4.19/arch/i386/mm/pageattr.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/i386/mm/pageattr.c linux-2.4.20/arch/i386/mm/pageattr.c
@@ -0,0 +1,175 @@
+/* 
+ * Copyright 2002 Andi Kleen, SuSE Labs. 
+ * Thanks to Ben LaHaise for precious feedback.
+ */ 
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+#include <asm/processor.h>
+
+/* Should move most of this stuff into the appropiate includes */
+#define LARGE_PAGE_MASK (~(LARGE_PAGE_SIZE-1))
+#define LARGE_PAGE_SIZE (1UL << PMD_SHIFT)
+
+static inline pte_t *lookup_address(unsigned long address) 
+{ 
+	pmd_t *pmd;	
+	pgd_t *pgd = pgd_offset(&init_mm, address); 
+
+	if (pgd_none(*pgd))
+		return NULL; 
+	if (pgd_val(*pgd) & _PAGE_PSE)
+		return (pte_t *)pgd; 
+	pmd = pmd_offset(pgd, address); 	       
+	if (pmd_none(*pmd))
+		return NULL; 
+	if (pmd_val(*pmd) & _PAGE_PSE) 
+		return (pte_t *)pmd; 
+    return pte_offset(pmd, address);
+} 
+
+static struct page *split_large_page(unsigned long address, pgprot_t prot)
+{ 
+	int i; 
+	unsigned long addr;
+	struct page *base = alloc_pages(GFP_KERNEL, 0);
+	pte_t *pbase;
+	if (!base) 
+		return NULL;
+	address = __pa(address);
+	addr = address & LARGE_PAGE_MASK; 
+	pbase = (pte_t *)page_address(base);
+	for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
+		pbase[i] = mk_pte_phys(addr, 
+				      addr == address ? prot : PAGE_KERNEL);
+	}
+	return base;
+} 
+
+static void flush_kernel_map(void * address) 
+{ 
+	if (!test_bit(X86_FEATURE_SELFSNOOP, boot_cpu_data.x86_capability)) {
+		/* Could use CLFLUSH here if the CPU supports it (Hammer,P4) */
+		if (boot_cpu_data.x86_model >= 4) 
+			asm volatile("wbinvd":::"memory"); 	
+	} 
+
+	/* Do global flush here to work around large page flushing errata 
+	   in some early Athlons */
+	__flush_tlb_all(); 	
+}
+
+static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte) 
+{ 
+	set_pte_atomic(kpte, pte); 	/* change init_mm */
+#ifndef CONFIG_X86_PAE
+	{
+		struct list_head *l;
+		spin_lock(&mmlist_lock);
+		list_for_each(l, &init_mm.mmlist) { 
+			struct mm_struct *mm = list_entry(l, struct mm_struct, mmlist);
+			pmd_t *pmd = pmd_offset(pgd_offset(mm, address), address);
+			set_pte_atomic((pte_t *)pmd, pte);
+		} 
+		spin_unlock(&mmlist_lock);
+	}
+#endif
+}
+
+/* no more special protections in this 2/4MB area - revert to a
+   large page again. */
+static inline void revert_page(struct page *kpte_page, unsigned long address)
+{
+	pte_t *linear = (pte_t *) 
+		pmd_offset(pgd_offset(&init_mm, address), address);
+	set_pmd_pte(linear,  address,
+		mk_pte_phys(__pa(address & LARGE_PAGE_MASK),
+			    MAKE_GLOBAL(_KERNPG_TABLE|_PAGE_PSE)));
+}	
+ 
+/*
+ * Change the page attributes of an page in the linear mapping.
+ *
+ * This should be used when a page is mapped with a different caching policy
+ * than write-back somewhere - some CPUs do not like it when mappings with
+ * different caching policies exist. This changes the page attributes of the
+ * in kernel linear mapping too.
+ * 
+ * The caller needs to ensure that there are no conflicting mappings elsewhere.
+ * This function only deals with the kernel linear map.
+ * When page is in highmem it must never be kmap'ed.
+ */
+static int 
+__change_page_attr(struct page *page, pgprot_t prot, struct page **oldpage) 
+{ 
+	pte_t *kpte; 
+	unsigned long address;
+	struct page *kpte_page;
+
+#ifdef CONFIG_HIGHMEM
+	if (page >= highmem_start_page) 
+		BUG(); 
+#endif
+	address = (unsigned long)page_address(page);
+	kpte = lookup_address(address);
+	if (!kpte) 
+		return -EINVAL; 
+	kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
+	if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) { 
+		if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
+			pte_t old = *kpte;
+			pte_t standard = mk_pte(page, PAGE_KERNEL); 
+
+			set_pte_atomic(kpte, mk_pte(page, prot)); 
+			if (pte_same(old,standard))
+				atomic_inc(&kpte_page->count);
+		} else {
+			struct page *split = split_large_page(address, prot); 
+			if (!split)
+				return -ENOMEM;
+			atomic_inc(&kpte_page->count); 	
+			set_pmd_pte(kpte,address,mk_pte(split, PAGE_KERNEL));
+		}	
+	} else if ((pte_val(*kpte) & _PAGE_PSE) == 0) { 
+		set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
+		atomic_dec(&kpte_page->count); 
+	}
+
+	if (cpu_has_pse && (atomic_read(&kpte_page->count) == 1)) { 
+		*oldpage = kpte_page;
+		revert_page(kpte_page, address);
+	} 
+	return 0;
+} 
+
+int change_page_attr(struct page *page, int numpages, pgprot_t prot)
+{
+	int err = 0; 
+	struct page *fpage; 
+	int i; 
+
+	down_write(&init_mm.mmap_sem);
+	for (i = 0; i < numpages; i++, page++) { 
+		fpage = NULL;
+		err = __change_page_attr(page, prot, &fpage); 
+		if (err) 
+			break; 
+		if (fpage || i == numpages-1) { 
+			void *address = page_address(page);
+#ifdef CONFIG_SMP 
+			smp_call_function(flush_kernel_map, address, 1, 1);
+#endif	
+			flush_kernel_map(address);
+			if (fpage)
+				__free_page(fpage);
+		} 
+	} 	
+	up_write(&init_mm.mmap_sem); 
+	return err;
+}
+
+EXPORT_SYMBOL(change_page_attr);