/* $NetBSD: convert_xmm_s87.c,v 1.8 2024/02/10 09:24:17 andvar Exp $ */ /*- * Copyright (c) 1998, 2000, 2001, 2008 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Charles M. Hannum; by Jason R. Thorpe of Wasabi Systems, Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ #include <sys/cdefs.h> __KERNEL_RCSID(0, "$NetBSD: convert_xmm_s87.c,v 1.8 2024/02/10 09:24:17 andvar Exp $"); #include <sys/param.h> #include <x86/fpu.h> void process_xmm_to_s87(const struct fxsave *sxmm, struct save87 *s87) { unsigned int tag, ab_tag, st; const struct fpaccfx *fx_reg; struct fpacc87 *s87_reg; int i; /* * For historic reasons core dumps and ptrace all use the old save87 * layout. Convert the important parts. * getucontext gets what we give it. * setucontext should return something given by getucontext, but * we are (at the moment) willing to change it. * * It really isn't worth setting the 'tag' bits to 01 (zero) or * 10 (NaN etc) since the processor will set any internal bits * correctly when the value is loaded (the 287 believed them). * * Additionally the s87_tw and s87_tw are 'indexed' by the actual * register numbers, whereas the registers themselves have ST(0) * first. Pairing the values and tags can only be done with * reference to the 'top of stack'. * * If any x87 registers are used, they will typically be from * r7 downwards - so the high bits of the tag register indicate * used registers. The conversions are not optimised for this. * * The ABI we use requires the FP stack to be empty on every * function call. I think this means that the stack isn't expected * to overflow - overflow doesn't drop a core in my testing. * * Note that this code writes to all of the 's87' structure that * actually gets written to userspace. */ /* FPU control/status */ s87->s87_cw = sxmm->fx_cw; s87->s87_sw = sxmm->fx_sw; /* tag word handled below */ s87->s87_ip = sxmm->fx_ip; s87->s87_opcode = sxmm->fx_opcode; s87->s87_dp = sxmm->fx_dp; /* FP registers (in stack order) */ fx_reg = sxmm->fx_87_ac; s87_reg = s87->s87_ac; for (i = 0; i < 8; fx_reg++, s87_reg++, i++) *s87_reg = fx_reg->r; /* Tag word and registers. */ ab_tag = sxmm->fx_tw & 0xff; /* Bits set if valid */ if (ab_tag == 0) { /* none used */ s87->s87_tw = 0xffff; return; } /* For ST(i), i = fpu_reg - top, we start with fpu_reg=7. */ st = 7 - ((sxmm->fx_sw >> 11) & 7); tag = 0; for (i = 0x80; i != 0; i >>= 1) { tag <<= 2; if (ab_tag & i) { unsigned int exp; /* Non-empty - we need to check ST(i) */ fx_reg = &sxmm->fx_87_ac[st]; exp = fx_reg->r.f87_exp_sign & 0x7fff; if (exp == 0) { if (fx_reg->r.f87_mantissa == 0) tag |= 1; /* Zero */ else tag |= 2; /* Denormal */ } else if (exp == 0x7fff) tag |= 2; /* Infinity or NaN */ } else tag |= 3; /* Empty */ st = (st - 1) & 7; } s87->s87_tw = tag; } void process_s87_to_xmm(const struct save87 *s87, struct fxsave *sxmm) { unsigned int tag, ab_tag; struct fpaccfx *fx_reg; const struct fpacc87 *s87_reg; int i; /* * ptrace gives us registers in the save87 format and * we must convert them to the correct format. * * This code is normally used when overwriting the processes * registers (in the pcb), so it mustn't change any other fields. * * There is a lot of pad in 'struct fxsave', if the destination * is written to userspace, it must be zeroed first. */ /* FPU control/status */ sxmm->fx_cw = s87->s87_cw; sxmm->fx_sw = s87->s87_sw; /* tag word handled below */ sxmm->fx_ip = s87->s87_ip; sxmm->fx_opcode = s87->s87_opcode; sxmm->fx_dp = s87->s87_dp; /* Tag word */ tag = s87->s87_tw; /* 0b11 => unused */ if (tag == 0xffff) { /* All unused - values don't matter, zero for safety */ sxmm->fx_tw = 0; memset(&sxmm->fx_87_ac, 0, sizeof sxmm->fx_87_ac); return; } tag ^= 0xffff; /* So 0b00 is unused */ tag |= tag >> 1; /* Look at even bits */ ab_tag = 0; i = 1; do ab_tag |= tag & i; while ((tag >>= 1) >= (i <<= 1)); sxmm->fx_tw = ab_tag; /* FP registers (in stack order) */ fx_reg = sxmm->fx_87_ac; s87_reg = s87->s87_ac; for (i = 0; i < 8; fx_reg++, s87_reg++, i++) fx_reg->r = *s87_reg; }
