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![Heiko Carstens](/assets/img/avatar_default.png)
When fixing the DAT off bug ("s390: fix DAT off memory access, e.g. on kdump") both Christian and I missed that we can save an additional stnsm instruction. This saves us a couple of cycles which could improve the speed of memcpy_real. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
212 lines
4.9 KiB
C
212 lines
4.9 KiB
C
/*
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* Access kernel memory without faulting -- s390 specific implementation.
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*
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* Copyright IBM Corp. 2009, 2015
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*
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* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
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*
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*/
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#include <linux/uaccess.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/gfp.h>
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#include <linux/cpu.h>
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#include <asm/ctl_reg.h>
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#include <asm/io.h>
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static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
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{
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unsigned long aligned, offset, count;
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char tmp[8];
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aligned = (unsigned long) dst & ~7UL;
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offset = (unsigned long) dst & 7UL;
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size = min(8UL - offset, size);
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count = size - 1;
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asm volatile(
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" bras 1,0f\n"
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" mvc 0(1,%4),0(%5)\n"
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"0: mvc 0(8,%3),0(%0)\n"
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" ex %1,0(1)\n"
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" lg %1,0(%3)\n"
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" lra %0,0(%0)\n"
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" sturg %1,%0\n"
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: "+&a" (aligned), "+&a" (count), "=m" (tmp)
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: "a" (&tmp), "a" (&tmp[offset]), "a" (src)
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: "cc", "memory", "1");
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return size;
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}
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/*
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* s390_kernel_write - write to kernel memory bypassing DAT
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* @dst: destination address
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* @src: source address
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* @size: number of bytes to copy
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*
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* This function writes to kernel memory bypassing DAT and possible page table
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* write protection. It writes to the destination using the sturg instruction.
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* Therefore we have a read-modify-write sequence: the function reads eight
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* bytes from destination at an eight byte boundary, modifies the bytes
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* requested and writes the result back in a loop.
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*
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* Note: this means that this function may not be called concurrently on
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* several cpus with overlapping words, since this may potentially
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* cause data corruption.
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*/
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void notrace s390_kernel_write(void *dst, const void *src, size_t size)
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{
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long copied;
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while (size) {
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copied = s390_kernel_write_odd(dst, src, size);
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dst += copied;
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src += copied;
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size -= copied;
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}
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}
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static int __memcpy_real(void *dest, void *src, size_t count)
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{
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register unsigned long _dest asm("2") = (unsigned long) dest;
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register unsigned long _len1 asm("3") = (unsigned long) count;
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register unsigned long _src asm("4") = (unsigned long) src;
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register unsigned long _len2 asm("5") = (unsigned long) count;
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int rc = -EFAULT;
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asm volatile (
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"0: mvcle %1,%2,0x0\n"
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"1: jo 0b\n"
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" lhi %0,0x0\n"
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"2:\n"
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EX_TABLE(1b,2b)
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: "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
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"+d" (_len2), "=m" (*((long *) dest))
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: "m" (*((long *) src))
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: "cc", "memory");
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return rc;
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}
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/*
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* Copy memory in real mode (kernel to kernel)
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*/
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int memcpy_real(void *dest, void *src, size_t count)
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{
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int irqs_disabled, rc;
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unsigned long flags;
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if (!count)
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return 0;
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flags = __arch_local_irq_stnsm(0xf8UL);
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irqs_disabled = arch_irqs_disabled_flags(flags);
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if (!irqs_disabled)
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trace_hardirqs_off();
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rc = __memcpy_real(dest, src, count);
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if (!irqs_disabled)
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trace_hardirqs_on();
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__arch_local_irq_ssm(flags);
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return rc;
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}
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/*
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* Copy memory in absolute mode (kernel to kernel)
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*/
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void memcpy_absolute(void *dest, void *src, size_t count)
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{
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unsigned long cr0, flags, prefix;
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flags = arch_local_irq_save();
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__ctl_store(cr0, 0, 0);
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__ctl_clear_bit(0, 28); /* disable lowcore protection */
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prefix = store_prefix();
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if (prefix) {
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local_mcck_disable();
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set_prefix(0);
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memcpy(dest, src, count);
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set_prefix(prefix);
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local_mcck_enable();
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} else {
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memcpy(dest, src, count);
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}
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__ctl_load(cr0, 0, 0);
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arch_local_irq_restore(flags);
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}
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/*
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* Copy memory from kernel (real) to user (virtual)
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*/
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int copy_to_user_real(void __user *dest, void *src, unsigned long count)
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{
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int offs = 0, size, rc;
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char *buf;
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buf = (char *) __get_free_page(GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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rc = -EFAULT;
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while (offs < count) {
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size = min(PAGE_SIZE, count - offs);
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if (memcpy_real(buf, src + offs, size))
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goto out;
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if (copy_to_user(dest + offs, buf, size))
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goto out;
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offs += size;
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}
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rc = 0;
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out:
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free_page((unsigned long) buf);
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return rc;
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}
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/*
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* Check if physical address is within prefix or zero page
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*/
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static int is_swapped(unsigned long addr)
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{
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unsigned long lc;
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int cpu;
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if (addr < sizeof(struct lowcore))
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return 1;
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for_each_online_cpu(cpu) {
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lc = (unsigned long) lowcore_ptr[cpu];
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if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
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continue;
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return 1;
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}
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return 0;
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}
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/*
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* Convert a physical pointer for /dev/mem access
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*
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* For swapped prefix pages a new buffer is returned that contains a copy of
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* the absolute memory. The buffer size is maximum one page large.
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*/
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void *xlate_dev_mem_ptr(phys_addr_t addr)
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{
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void *bounce = (void *) addr;
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unsigned long size;
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get_online_cpus();
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preempt_disable();
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if (is_swapped(addr)) {
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size = PAGE_SIZE - (addr & ~PAGE_MASK);
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bounce = (void *) __get_free_page(GFP_ATOMIC);
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if (bounce)
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memcpy_absolute(bounce, (void *) addr, size);
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}
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preempt_enable();
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put_online_cpus();
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return bounce;
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}
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/*
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* Free converted buffer for /dev/mem access (if necessary)
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*/
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void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
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{
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if ((void *) addr != buf)
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free_page((unsigned long) buf);
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}
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