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The decoder library uses variable length arrays on stack. To get rid of them it would be simple to allocate fixed length arrays on stack, but those might become rather large. The other solution is to allocate the buffers in the rs control structure, but this cannot be done as long as the structure can be shared by several users. Sharing is desired because the RS polynom tables are large and initialization is time consuming. To solve this split the codec information out of the control structure and have a pointer to a shared codec in it. Instantiate the control structure for each user, create a new codec if no shareable is avaiable yet. Adjust all affected usage sites to the new scheme. This allows to add per instance decoder buffers to the control structure later on. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Boris Brezillon <boris.brezillon@bootlin.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Kees Cook <keescook@chromium.org> Cc: Segher Boessenkool <segher@kernel.crashing.org> Cc: Kernel Hardening <kernel-hardening@lists.openwall.com> Cc: Richard Weinberger <richard@nod.at> Cc: Mike Snitzer <snitzer@redhat.com> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Colin Cross <ccross@android.com> Cc: Andrew Morton <akpm@linuxfoundation.org> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Alasdair Kergon <agk@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org>
129 lines
3.6 KiB
C
129 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Generic Reed Solomon encoder / decoder library
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*
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* Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de)
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*
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* RS code lifted from reed solomon library written by Phil Karn
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* Copyright 2002 Phil Karn, KA9Q
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*/
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#ifndef _RSLIB_H_
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#define _RSLIB_H_
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#include <linux/list.h>
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#include <linux/types.h> /* for gfp_t */
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#include <linux/gfp.h> /* for GFP_KERNEL */
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/**
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* struct rs_codec - rs codec data
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*
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* @mm: Bits per symbol
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* @nn: Symbols per block (= (1<<mm)-1)
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* @alpha_to: log lookup table
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* @index_of: Antilog lookup table
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* @genpoly: Generator polynomial
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* @nroots: Number of generator roots = number of parity symbols
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* @fcr: First consecutive root, index form
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* @prim: Primitive element, index form
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* @iprim: prim-th root of 1, index form
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* @gfpoly: The primitive generator polynominal
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* @gffunc: Function to generate the field, if non-canonical representation
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* @users: Users of this structure
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* @list: List entry for the rs codec list
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*/
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struct rs_codec {
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int mm;
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int nn;
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uint16_t *alpha_to;
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uint16_t *index_of;
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uint16_t *genpoly;
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int nroots;
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int fcr;
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int prim;
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int iprim;
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int gfpoly;
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int (*gffunc)(int);
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int users;
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struct list_head list;
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};
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/**
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* struct rs_control - rs control structure per instance
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* @codec: The codec used for this instance
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*/
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struct rs_control {
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struct rs_codec *codec;
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};
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/* General purpose RS codec, 8-bit data width, symbol width 1-15 bit */
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#ifdef CONFIG_REED_SOLOMON_ENC8
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int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par,
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uint16_t invmsk);
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#endif
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#ifdef CONFIG_REED_SOLOMON_DEC8
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int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len,
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uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
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uint16_t *corr);
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#endif
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/* General purpose RS codec, 16-bit data width, symbol width 1-15 bit */
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#ifdef CONFIG_REED_SOLOMON_ENC16
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int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par,
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uint16_t invmsk);
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#endif
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#ifdef CONFIG_REED_SOLOMON_DEC16
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int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len,
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uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
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uint16_t *corr);
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#endif
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struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim,
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int nroots, gfp_t gfp);
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/**
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* init_rs - Create a RS control struct and initialize it
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* @symsize: the symbol size (number of bits)
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* @gfpoly: the extended Galois field generator polynomial coefficients,
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* with the 0th coefficient in the low order bit. The polynomial
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* must be primitive;
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* @fcr: the first consecutive root of the rs code generator polynomial
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* in index form
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* @prim: primitive element to generate polynomial roots
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* @nroots: RS code generator polynomial degree (number of roots)
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*
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* Allocations use GFP_KERNEL.
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*/
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static inline struct rs_control *init_rs(int symsize, int gfpoly, int fcr,
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int prim, int nroots)
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{
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return init_rs_gfp(symsize, gfpoly, fcr, prim, nroots, GFP_KERNEL);
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}
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struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
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int fcr, int prim, int nroots);
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/* Release a rs control structure */
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void free_rs(struct rs_control *rs);
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/** modulo replacement for galois field arithmetics
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*
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* @rs: Pointer to the RS codec
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* @x: the value to reduce
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*
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* where
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* rs->mm = number of bits per symbol
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* rs->nn = (2^rs->mm) - 1
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*
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* Simple arithmetic modulo would return a wrong result for values
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* >= 3 * rs->nn
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*/
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static inline int rs_modnn(struct rs_codec *rs, int x)
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{
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while (x >= rs->nn) {
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x -= rs->nn;
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x = (x >> rs->mm) + (x & rs->nn);
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}
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return x;
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}
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#endif
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