9b1a735de6
This commit adds the logic to patch alternative sections. This is fairly straightforward, except for branches. Relative branches that jump from inside the else section to outside of it need to be translated as they're moved, otherwise they will jump to the wrong location. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Paul Mackerras <paulus@samba.org>
110 lines
2.6 KiB
C
110 lines
2.6 KiB
C
/*
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* Copyright (C) 2001 Ben. Herrenschmidt (benh@kernel.crashing.org)
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*
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* Modifications for ppc64:
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* Copyright (C) 2003 Dave Engebretsen <engebret@us.ibm.com>
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*
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* Copyright 2008 Michael Ellerman, IBM Corporation.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <asm/cputable.h>
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#include <asm/code-patching.h>
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struct fixup_entry {
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unsigned long mask;
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unsigned long value;
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long start_off;
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long end_off;
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long alt_start_off;
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long alt_end_off;
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};
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static unsigned int *calc_addr(struct fixup_entry *fcur, long offset)
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{
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/*
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* We store the offset to the code as a negative offset from
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* the start of the alt_entry, to support the VDSO. This
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* routine converts that back into an actual address.
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*/
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return (unsigned int *)((unsigned long)fcur + offset);
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}
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static int patch_alt_instruction(unsigned int *src, unsigned int *dest,
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unsigned int *alt_start, unsigned int *alt_end)
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{
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unsigned int instr;
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instr = *src;
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if (instr_is_relative_branch(*src)) {
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unsigned int *target = (unsigned int *)branch_target(src);
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/* Branch within the section doesn't need translating */
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if (target < alt_start || target >= alt_end) {
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instr = translate_branch(dest, src);
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if (!instr)
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return 1;
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}
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}
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patch_instruction(dest, instr);
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return 0;
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}
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static int patch_feature_section(unsigned long value, struct fixup_entry *fcur)
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{
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unsigned int *start, *end, *alt_start, *alt_end, *src, *dest;
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start = calc_addr(fcur, fcur->start_off);
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end = calc_addr(fcur, fcur->end_off);
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alt_start = calc_addr(fcur, fcur->alt_start_off);
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alt_end = calc_addr(fcur, fcur->alt_end_off);
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if ((alt_end - alt_start) > (end - start))
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return 1;
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if ((value & fcur->mask) == fcur->value)
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return 0;
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src = alt_start;
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dest = start;
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for (; src < alt_end; src++, dest++) {
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if (patch_alt_instruction(src, dest, alt_start, alt_end))
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return 1;
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}
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for (; dest < end; dest++)
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patch_instruction(dest, PPC_NOP_INSTR);
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return 0;
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}
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void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end)
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{
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struct fixup_entry *fcur, *fend;
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fcur = fixup_start;
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fend = fixup_end;
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for (; fcur < fend; fcur++) {
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if (patch_feature_section(value, fcur)) {
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__WARN();
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printk("Unable to patch feature section at %p - %p" \
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" with %p - %p\n",
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calc_addr(fcur, fcur->start_off),
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calc_addr(fcur, fcur->end_off),
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calc_addr(fcur, fcur->alt_start_off),
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calc_addr(fcur, fcur->alt_end_off));
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}
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}
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}
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