053a858efa
If you pass a target value to create_branch() which is more than 32MB - 4, or - 32MB away from the branch site, then it's impossible to create an immediate branch. The current code doesn't check, which will lead to us creating a branch to somewhere else - which is bad. For code that cares to check we return 0, which is easy to check for, and for code that doesn't at least we'll be creating an illegal instruction, rather than a branch to some random address. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Acked-by: Kumar Gala <galak@kernel.crashing.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
43 lines
1.2 KiB
C
43 lines
1.2 KiB
C
/*
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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/code-patching.h>
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void patch_instruction(unsigned int *addr, unsigned int instr)
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{
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*addr = instr;
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asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
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}
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void patch_branch(unsigned int *addr, unsigned long target, int flags)
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{
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patch_instruction(addr, create_branch(addr, target, flags));
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}
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unsigned int create_branch(const unsigned int *addr,
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unsigned long target, int flags)
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{
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unsigned int instruction;
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long offset;
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offset = target;
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if (! (flags & BRANCH_ABSOLUTE))
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offset = offset - (unsigned long)addr;
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/* Check we can represent the target in the instruction format */
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if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
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return 0;
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/* Mask out the flags and target, so they don't step on each other. */
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instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
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return instruction;
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}
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