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ee9f8fce99
Add the new ORC unwinder which is enabled by CONFIG_ORC_UNWINDER=y. It plugs into the existing x86 unwinder framework. It relies on objtool to generate the needed .orc_unwind and .orc_unwind_ip sections. For more details on why ORC is used instead of DWARF, see Documentation/x86/orc-unwinder.txt - but the short version is that it's a simplified, fundamentally more robust debugninfo data structure, which also allows up to two orders of magnitude faster lookups than the DWARF unwinder - which matters to profiling workloads like perf. Thanks to Andy Lutomirski for the performance improvement ideas: splitting the ORC unwind table into two parallel arrays and creating a fast lookup table to search a subset of the unwind table. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/0a6cbfb40f8da99b7a45a1a8302dc6aef16ec812.1500938583.git.jpoimboe@redhat.com [ Extended the changelog. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
47 lines
1.6 KiB
C
47 lines
1.6 KiB
C
/*
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* Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
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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 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _ORC_LOOKUP_H
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#define _ORC_LOOKUP_H
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/*
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* This is a lookup table for speeding up access to the .orc_unwind table.
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* Given an input address offset, the corresponding lookup table entry
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* specifies a subset of the .orc_unwind table to search.
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*
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* Each block represents the end of the previous range and the start of the
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* next range. An extra block is added to give the last range an end.
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*
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* The block size should be a power of 2 to avoid a costly 'div' instruction.
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*
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* A block size of 256 was chosen because it roughly doubles unwinder
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* performance while only adding ~5% to the ORC data footprint.
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*/
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#define LOOKUP_BLOCK_ORDER 8
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#define LOOKUP_BLOCK_SIZE (1 << LOOKUP_BLOCK_ORDER)
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#ifndef LINKER_SCRIPT
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extern unsigned int orc_lookup[];
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extern unsigned int orc_lookup_end[];
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#define LOOKUP_START_IP (unsigned long)_stext
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#define LOOKUP_STOP_IP (unsigned long)_etext
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#endif /* LINKER_SCRIPT */
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#endif /* _ORC_LOOKUP_H */
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