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2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc

 kernel/arch/sparc/mm/highmem.c
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+// SPDX-License-Identifier: GPL-2.0
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+/*
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+ *  highmem.c: virtual kernel memory mappings for high memory
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+ *
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+ *  Provides kernel-static versions of atomic kmap functions originally
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+ *  found as inlines in include/asm-sparc/highmem.h.  These became
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+ *  needed as kmap_atomic() and kunmap_atomic() started getting
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+ *  called from within modules.
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+ *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
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+ *
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+ *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
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+ *  modules because they are loaded with btfixup-ped functions.
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+ */
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+
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+/*
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+ * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
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+ * gives a more generic (and caching) interface. But kmap_atomic can
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+ * be used in IRQ contexts, so in some (very limited) cases we need it.
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+ *
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+ * XXX This is an old text. Actually, it's good to use atomic kmaps,
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+ * provided you remember that they are atomic and not try to sleep
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+ * with a kmap taken, much like a spinlock. Non-atomic kmaps are
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+ * shared by CPUs, and so precious, and establishing them requires IPI.
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+ * Atomic kmaps are lightweight and we may have NCPUS more of them.
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+ */
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+#include <linux/highmem.h>
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+#include <linux/export.h>
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+#include <linux/mm.h>
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+
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+#include <asm/cacheflush.h>
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+#include <asm/tlbflush.h>
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+#include <asm/vaddrs.h>
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+
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+static pte_t *kmap_pte;
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+
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+void __init kmap_init(void)
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+{
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+	unsigned long address = __fix_to_virt(FIX_KMAP_BEGIN);
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+
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+        /* cache the first kmap pte */
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+        kmap_pte = virt_to_kpte(address);
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+}
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+
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+void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
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+{
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+	unsigned long vaddr;
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+	long idx, type;
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+
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+	type = kmap_atomic_idx_push();
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+	idx = type + KM_TYPE_NR*smp_processor_id();
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+	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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+
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+/* XXX Fix - Anton */
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+#if 0
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+	__flush_cache_one(vaddr);
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+#else
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+	flush_cache_all();
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+#endif
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+
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+#ifdef CONFIG_DEBUG_HIGHMEM
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+	BUG_ON(!pte_none(*(kmap_pte-idx)));
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+#endif
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+	set_pte(kmap_pte-idx, mk_pte(page, prot));
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+/* XXX Fix - Anton */
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+#if 0
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+	__flush_tlb_one(vaddr);
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+#else
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+	flush_tlb_all();
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+#endif
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+
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+	return (void*) vaddr;
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+}
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+EXPORT_SYMBOL(kmap_atomic_high_prot);
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+
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+void kunmap_atomic_high(void *kvaddr)
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+{
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+	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
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+	int type;
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+
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+	if (vaddr < FIXADDR_START)
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+		return;
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+
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+	type = kmap_atomic_idx();
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+
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+#ifdef CONFIG_DEBUG_HIGHMEM
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+	{
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+		unsigned long idx;
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+
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+		idx = type + KM_TYPE_NR * smp_processor_id();
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+		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
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+
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+		/* XXX Fix - Anton */
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+#if 0
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+		__flush_cache_one(vaddr);
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+#else
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+		flush_cache_all();
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+#endif
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+
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+		/*
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+		 * force other mappings to Oops if they'll try to access
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+		 * this pte without first remap it
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+		 */
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+		pte_clear(&init_mm, vaddr, kmap_pte-idx);
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+		/* XXX Fix - Anton */
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+#if 0
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+		__flush_tlb_one(vaddr);
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+#else
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+		flush_tlb_all();
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+#endif
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+	}
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+#endif
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+
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+	kmap_atomic_idx_pop();
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+}
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+EXPORT_SYMBOL(kunmap_atomic_high);