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https://github.com/torvalds/linux
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08b36c4a02
Presently trapped I/O is only registered if it's not explicitly disabled for the platforms that select it openly. From the fault path this runs through an address lookup before figuring out that nothing matches and falls back through the error path, but we can forego the lookup completely by testing if it's been explicitly disabled. This provides a measurable speedup for things like qemu that rely on runtime disabling. Signed-off-by: Paul Mundt <lethal@linux-sh.org>
294 lines
6.4 KiB
C
294 lines
6.4 KiB
C
/*
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* Trapped io support
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*
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* Copyright (C) 2008 Magnus Damm
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*
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* Intercept io operations by trapping.
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*/
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/bitops.h>
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#include <linux/vmalloc.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <asm/system.h>
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#include <asm/mmu_context.h>
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#include <asm/uaccess.h>
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#include <asm/io.h>
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#include <asm/io_trapped.h>
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#define TRAPPED_PAGES_MAX 16
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#ifdef CONFIG_HAS_IOPORT
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LIST_HEAD(trapped_io);
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EXPORT_SYMBOL_GPL(trapped_io);
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#endif
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#ifdef CONFIG_HAS_IOMEM
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LIST_HEAD(trapped_mem);
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EXPORT_SYMBOL_GPL(trapped_mem);
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#endif
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static DEFINE_SPINLOCK(trapped_lock);
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static int trapped_io_disable __read_mostly;
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static int __init trapped_io_setup(char *__unused)
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{
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trapped_io_disable = 1;
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return 1;
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}
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__setup("noiotrap", trapped_io_setup);
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int register_trapped_io(struct trapped_io *tiop)
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{
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struct resource *res;
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unsigned long len = 0, flags = 0;
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struct page *pages[TRAPPED_PAGES_MAX];
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int k, n;
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if (unlikely(trapped_io_disable))
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return 0;
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/* structure must be page aligned */
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if ((unsigned long)tiop & (PAGE_SIZE - 1))
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goto bad;
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for (k = 0; k < tiop->num_resources; k++) {
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res = tiop->resource + k;
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len += roundup((res->end - res->start) + 1, PAGE_SIZE);
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flags |= res->flags;
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}
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/* support IORESOURCE_IO _or_ MEM, not both */
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if (hweight_long(flags) != 1)
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goto bad;
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n = len >> PAGE_SHIFT;
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if (n >= TRAPPED_PAGES_MAX)
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goto bad;
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for (k = 0; k < n; k++)
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pages[k] = virt_to_page(tiop);
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tiop->virt_base = vmap(pages, n, VM_MAP, PAGE_NONE);
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if (!tiop->virt_base)
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goto bad;
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len = 0;
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for (k = 0; k < tiop->num_resources; k++) {
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res = tiop->resource + k;
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pr_info("trapped io 0x%08lx overrides %s 0x%08lx\n",
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(unsigned long)(tiop->virt_base + len),
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res->flags & IORESOURCE_IO ? "io" : "mmio",
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(unsigned long)res->start);
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len += roundup((res->end - res->start) + 1, PAGE_SIZE);
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}
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tiop->magic = IO_TRAPPED_MAGIC;
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INIT_LIST_HEAD(&tiop->list);
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spin_lock_irq(&trapped_lock);
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if (flags & IORESOURCE_IO)
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list_add(&tiop->list, &trapped_io);
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if (flags & IORESOURCE_MEM)
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list_add(&tiop->list, &trapped_mem);
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spin_unlock_irq(&trapped_lock);
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return 0;
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bad:
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pr_warning("unable to install trapped io filter\n");
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return -1;
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}
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EXPORT_SYMBOL_GPL(register_trapped_io);
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void __iomem *match_trapped_io_handler(struct list_head *list,
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unsigned long offset,
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unsigned long size)
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{
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unsigned long voffs;
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struct trapped_io *tiop;
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struct resource *res;
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int k, len;
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unsigned long flags;
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spin_lock_irqsave(&trapped_lock, flags);
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list_for_each_entry(tiop, list, list) {
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voffs = 0;
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for (k = 0; k < tiop->num_resources; k++) {
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res = tiop->resource + k;
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if (res->start == offset) {
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spin_unlock_irqrestore(&trapped_lock, flags);
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return tiop->virt_base + voffs;
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}
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len = (res->end - res->start) + 1;
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voffs += roundup(len, PAGE_SIZE);
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}
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}
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spin_unlock_irqrestore(&trapped_lock, flags);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(match_trapped_io_handler);
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static struct trapped_io *lookup_tiop(unsigned long address)
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{
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pgd_t *pgd_k;
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pud_t *pud_k;
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pmd_t *pmd_k;
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pte_t *pte_k;
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pte_t entry;
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pgd_k = swapper_pg_dir + pgd_index(address);
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if (!pgd_present(*pgd_k))
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return NULL;
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pud_k = pud_offset(pgd_k, address);
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if (!pud_present(*pud_k))
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return NULL;
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pmd_k = pmd_offset(pud_k, address);
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if (!pmd_present(*pmd_k))
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return NULL;
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pte_k = pte_offset_kernel(pmd_k, address);
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entry = *pte_k;
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return pfn_to_kaddr(pte_pfn(entry));
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}
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static unsigned long lookup_address(struct trapped_io *tiop,
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unsigned long address)
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{
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struct resource *res;
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unsigned long vaddr = (unsigned long)tiop->virt_base;
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unsigned long len;
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int k;
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for (k = 0; k < tiop->num_resources; k++) {
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res = tiop->resource + k;
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len = roundup((res->end - res->start) + 1, PAGE_SIZE);
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if (address < (vaddr + len))
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return res->start + (address - vaddr);
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vaddr += len;
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}
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return 0;
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}
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static unsigned long long copy_word(unsigned long src_addr, int src_len,
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unsigned long dst_addr, int dst_len)
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{
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unsigned long long tmp = 0;
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switch (src_len) {
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case 1:
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tmp = __raw_readb(src_addr);
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break;
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case 2:
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tmp = __raw_readw(src_addr);
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break;
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case 4:
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tmp = __raw_readl(src_addr);
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break;
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case 8:
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tmp = __raw_readq(src_addr);
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break;
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}
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switch (dst_len) {
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case 1:
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__raw_writeb(tmp, dst_addr);
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break;
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case 2:
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__raw_writew(tmp, dst_addr);
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break;
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case 4:
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__raw_writel(tmp, dst_addr);
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break;
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case 8:
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__raw_writeq(tmp, dst_addr);
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break;
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}
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return tmp;
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}
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static unsigned long from_device(void *dst, const void *src, unsigned long cnt)
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{
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struct trapped_io *tiop;
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unsigned long src_addr = (unsigned long)src;
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unsigned long long tmp;
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pr_debug("trapped io read 0x%08lx (%ld)\n", src_addr, cnt);
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tiop = lookup_tiop(src_addr);
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WARN_ON(!tiop || (tiop->magic != IO_TRAPPED_MAGIC));
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src_addr = lookup_address(tiop, src_addr);
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if (!src_addr)
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return cnt;
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tmp = copy_word(src_addr,
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max_t(unsigned long, cnt,
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(tiop->minimum_bus_width / 8)),
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(unsigned long)dst, cnt);
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pr_debug("trapped io read 0x%08lx -> 0x%08llx\n", src_addr, tmp);
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return 0;
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}
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static unsigned long to_device(void *dst, const void *src, unsigned long cnt)
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{
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struct trapped_io *tiop;
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unsigned long dst_addr = (unsigned long)dst;
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unsigned long long tmp;
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pr_debug("trapped io write 0x%08lx (%ld)\n", dst_addr, cnt);
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tiop = lookup_tiop(dst_addr);
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WARN_ON(!tiop || (tiop->magic != IO_TRAPPED_MAGIC));
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dst_addr = lookup_address(tiop, dst_addr);
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if (!dst_addr)
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return cnt;
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tmp = copy_word((unsigned long)src, cnt,
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dst_addr, max_t(unsigned long, cnt,
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(tiop->minimum_bus_width / 8)));
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pr_debug("trapped io write 0x%08lx -> 0x%08llx\n", dst_addr, tmp);
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return 0;
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}
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static struct mem_access trapped_io_access = {
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from_device,
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to_device,
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};
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int handle_trapped_io(struct pt_regs *regs, unsigned long address)
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{
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mm_segment_t oldfs;
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insn_size_t instruction;
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int tmp;
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if (trapped_io_disable)
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return 0;
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if (!lookup_tiop(address))
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return 0;
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WARN_ON(user_mode(regs));
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oldfs = get_fs();
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set_fs(KERNEL_DS);
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if (copy_from_user(&instruction, (void *)(regs->pc),
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sizeof(instruction))) {
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set_fs(oldfs);
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return 0;
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}
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tmp = handle_unaligned_access(instruction, regs,
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&trapped_io_access, 1);
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set_fs(oldfs);
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return tmp == 0;
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}
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