62 lines
1.4 KiB
C
62 lines
1.4 KiB
C
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/*
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* Access kernel memory without faulting -- s390 specific implementation.
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*
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* Copyright IBM Corp. 2009
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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 <asm/system.h>
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/*
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* This function writes to kernel memory bypassing DAT and possible
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* write protection. It copies one to four bytes from src to dst
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* using the stura instruction.
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* Returns the number of bytes copied or -EFAULT.
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*/
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static long probe_kernel_write_odd(void *dst, void *src, size_t size)
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{
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unsigned long count, aligned;
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int offset, mask;
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int rc = -EFAULT;
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aligned = (unsigned long) dst & ~3UL;
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offset = (unsigned long) dst & 3;
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count = min_t(unsigned long, 4 - offset, size);
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mask = (0xf << (4 - count)) & 0xf;
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mask >>= offset;
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asm volatile(
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" bras 1,0f\n"
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" icm 0,0,0(%3)\n"
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"0: l 0,0(%1)\n"
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" lra %1,0(%1)\n"
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"1: ex %2,0(1)\n"
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"2: stura 0,%1\n"
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" la %0,0\n"
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"3:\n"
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EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
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: "+d" (rc), "+a" (aligned)
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: "a" (mask), "a" (src) : "cc", "memory", "0", "1");
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return rc ? rc : count;
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}
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long probe_kernel_write(void *dst, void *src, size_t size)
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{
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long copied = 0;
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while (size) {
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copied = probe_kernel_write_odd(dst, src, size);
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if (copied < 0)
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break;
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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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return copied < 0 ? -EFAULT : 0;
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}
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