/* * highmem.c: virtual kernel memory mappings for high memory * * Provides kernel-static versions of atomic kmap functions originally * found as inlines in include/asm-sparc/highmem.h. These became * needed as kmap_atomic() and kunmap_atomic() started getting * called from within modules. * -- Tomas Szepe <szepe@pinerecords.com>, September 2002 * * But kmap_atomic() and kunmap_atomic() cannot be inlined in * modules because they are loaded with btfixup-ped functions. */ /* * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap * gives a more generic (and caching) interface. But kmap_atomic can * be used in IRQ contexts, so in some (very limited) cases we need it. * * XXX This is an old text. Actually, it's good to use atomic kmaps, * provided you remember that they are atomic and not try to sleep * with a kmap taken, much like a spinlock. Non-atomic kmaps are * shared by CPUs, and so precious, and establishing them requires IPI. * Atomic kmaps are lightweight and we may have NCPUS more of them. */ #include <linux/mm.h> #include <linux/highmem.h> #include <asm/pgalloc.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> #include <asm/fixmap.h> void *kmap_atomic(struct page *page, enum km_type type) { unsigned long idx; unsigned long vaddr; /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */ inc_preempt_count(); if (!PageHighMem(page)) return page_address(page); idx = type + KM_TYPE_NR*smp_processor_id(); vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); /* XXX Fix - Anton */ #if 0 __flush_cache_one(vaddr); #else flush_cache_all(); #endif #ifdef CONFIG_DEBUG_HIGHMEM BUG_ON(!pte_none(*(kmap_pte-idx))); #endif set_pte(kmap_pte-idx, mk_pte(page, kmap_prot)); /* XXX Fix - Anton */ #if 0 __flush_tlb_one(vaddr); #else flush_tlb_all(); #endif return (void*) vaddr; } void kunmap_atomic(void *kvaddr, enum km_type type) { #ifdef CONFIG_DEBUG_HIGHMEM unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK; unsigned long idx = type + KM_TYPE_NR*smp_processor_id(); if (vaddr < FIXADDR_START) { // FIXME dec_preempt_count(); preempt_check_resched(); return; } BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx)); /* XXX Fix - Anton */ #if 0 __flush_cache_one(vaddr); #else flush_cache_all(); #endif /* * force other mappings to Oops if they'll try to access * this pte without first remap it */ pte_clear(&init_mm, vaddr, kmap_pte-idx); /* XXX Fix - Anton */ #if 0 __flush_tlb_one(vaddr); #else flush_tlb_all(); #endif #endif dec_preempt_count(); preempt_check_resched(); } /* We may be fed a pagetable here by ptep_to_xxx and others. */ struct page *kmap_atomic_to_page(void *ptr) { unsigned long idx, vaddr = (unsigned long)ptr; pte_t *pte; if (vaddr < SRMMU_NOCACHE_VADDR) return virt_to_page(ptr); if (vaddr < PKMAP_BASE) return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT); BUG_ON(vaddr < FIXADDR_START); BUG_ON(vaddr > FIXADDR_TOP); idx = virt_to_fix(vaddr); pte = kmap_pte - (idx - FIX_KMAP_BEGIN); return pte_page(*pte); }