1 /* $NetBSD: cpu_extended_state.h,v 1.10 2016/08/18 13:00:54 maxv Exp $ */ 2 3 #ifndef _X86_CPU_EXTENDED_STATE_H_ 4 #define _X86_CPU_EXTENDED_STATE_H_ 5 6 #ifdef __lint__ 7 /* Lint has different packing rules and doesn't understand __aligned() */ 8 #define __CTASSERT_NOLINT(x) __CTASSERT(1) 9 #else 10 #define __CTASSERT_NOLINT(x) __CTASSERT(x) 11 #endif 12 13 /* 14 * This file contains definitions of structures that match the memory layouts 15 * used on x86 processors to save floating point registers and other extended 16 * cpu states. 17 * 18 * This includes registers (etc) used by SSE/SSE2/SSE3/SSSE3/SSE4 and the later 19 * AVX instructions. 20 * 21 * The definitions are such that any future 'extended state' should be handled 22 * (provided the kernel doesn't need to know the actual contents). 23 * 24 * The actual structures the cpu accesses must be aligned to 16 bytes for FXSAVE 25 * and 64 for XSAVE. The types aren't aligned because copies do not need extra 26 * alignment. 27 * 28 * The slightly different layout saved by the i387 fsave is also defined. 29 * This is only normally written by pre Pentium II type cpus that don't 30 * support the fxsave instruction. 31 * 32 * Associated save instructions: 33 * FNSAVE: Saves x87 state in 108 bytes (original i387 layout). 34 * Then reinitializes the fpu. 35 * FSAVE: Encodes to FWAIT followed by FNSAVE. 36 * FXSAVE: Saves the x87 state and XMM (aka SSE) registers to the 37 * first 448 (max) bytes of a 512 byte area. 38 * This layout does not match that written by FNSAVE. 39 * XSAVE: Uses the same layout for the x87 and XMM registers, 40 * followed by a 64byte header and separate save areas 41 * for additional extended cpu state. 42 * The x87 state is always saved, the others conditionally. 43 * XSAVEOPT: As XSAVE but only writes the registers blocks that have been 44 * modified. 45 */ 46 47 /* 48 * Layout for code/data pointers relating to FP exceptions. Marked 'packed' 49 * because they aren't always 64bit aligned. Since the x86 cpu supports 50 * misaligned accesses it isn't worth avoiding the 'packed' attribute. 51 */ 52 union fp_addr { 53 uint64_t fa_64; /* Linear address for 64bit systems */ 54 struct { 55 uint32_t fa_off; /* linear address for 32 bit */ 56 uint16_t fa_seg; /* code/data (etc) segment */ 57 uint16_t fa_opcode; /* last opcode (sometimes) */ 58 } fa_32; 59 } __packed __aligned(4); 60 61 /* The x87 registers are 80 bits */ 62 struct fpacc87 { 63 uint64_t f87_mantissa; /* mantissa */ 64 uint16_t f87_exp_sign; /* exponent and sign */ 65 } __packed __aligned(2); 66 67 /* The x87 registers padded out to 16 bytes for fxsave */ 68 struct fpaccfx { 69 struct fpacc87 r __aligned(16); 70 }; 71 72 /* The SSE/SSE2 registers are 128 bits */ 73 struct xmmreg { 74 uint8_t xmm_bytes[16]; 75 }; 76 77 /* The AVX registers are 256 bits, but the low bits are the xmmregs */ 78 struct ymmreg { 79 uint8_t ymm_bytes[16]; 80 }; 81 82 /* 83 * Floating point unit registers (fsave instruction). 84 * The s87_ac[] and fx_87_ac[] are relative to the stack top. 85 * The 'tag word' contains 2 bits per register and refers to absolute register 86 * numbers. 87 * The cpu sets the tag values 0b01 (zero) and 0b10 (special) when a value 88 * is loaded. The software need only set 0b00 (used) and 0xb11 (unused). 89 * The fxsave 'Abridged tag word' in inverted. 90 */ 91 struct save87 { 92 uint16_t s87_cw __aligned(4); /* control word */ 93 uint16_t s87_sw __aligned(4); /* status word */ 94 uint16_t s87_tw __aligned(4); /* tag word */ 95 union fp_addr s87_ip; /* floating point instruction pointer */ 96 #define s87_opcode s87_ip.fa_32.fa_opcode /* opcode last executed (11bits) */ 97 union fp_addr s87_dp; /* floating operand offset */ 98 struct fpacc87 s87_ac[8]; /* accumulator contents */ 99 }; 100 __CTASSERT_NOLINT(sizeof(struct save87) == 108); 101 102 /* 103 * FPU/MMX/SSE/SSE2 context 104 */ 105 struct fxsave { 106 uint16_t fx_cw; /* FPU Control Word */ 107 uint16_t fx_sw; /* FPU Status Word */ 108 uint8_t fx_tw; /* FPU Tag Word (abridged) */ 109 uint16_t fx_opcode; /* FPU Opcode */ 110 union fp_addr fx_ip; /* FPU Instruction Pointer */ 111 union fp_addr fx_dp; /* FPU Data pointer */ 112 uint32_t fx_mxcsr; /* MXCSR Register State */ 113 uint32_t fx_mxcsr_mask; 114 struct fpaccfx fx_87_ac[8]; /* 8 x87 registers */ 115 struct xmmreg fx_xmm[16]; /* XMM regs (8 in 32bit modes) */ 116 uint8_t fx_rsvd[48]; 117 uint8_t fx_kernel[48]; /* Not written by the hardware */ 118 } __aligned(16); 119 __CTASSERT_NOLINT(sizeof(struct fxsave) == 512); 120 121 /* 122 * The end of the fsave buffer can be used by the operating system 123 */ 124 struct fxsave_os { 125 uint8_t fxo_fxsave[512 - 48]; 126 /* 48 bytes available, NB copied to/from userspace */ 127 uint16_t fxo_dflt_cw; /* Control word for signal handlers */ 128 }; 129 130 /* 131 * For XSAVE, a 64byte header follows the fxsave data. 132 */ 133 struct xsave_header { 134 uint64_t xsh_fxsave[64]; /* to align in the union */ 135 uint64_t xsh_xstate_bv; /* bitmap of saved sub structures */ 136 uint64_t xsh_rsrvd[2]; /* must be zero */ 137 uint64_t xsh_reserved[5]; /* best if zero */ 138 }; 139 __CTASSERT(sizeof(struct xsave_header) == 512 + 64); 140 141 /* 142 * The ymm save area actually follows the xsave_header. 143 */ 144 struct xsave_ymm { 145 struct ymmreg xs_ymm[16]; /* High bits of YMM registers */ 146 }; 147 __CTASSERT(sizeof(struct xsave_ymm) == 256); 148 149 /* 150 * The following union is placed at the end of the pcb. 151 * It is defined this way to separate the definitions and to 152 * minimise the number of union/struct selectors. 153 * NB: Some userspace stuff (eg firefox) uses it to parse ucontext. 154 */ 155 union savefpu { 156 struct save87 sv_87; 157 struct fxsave sv_xmm; 158 #ifdef _KERNEL 159 struct fxsave_os sv_os; 160 struct xsave_header sv_xsave_hdr; 161 #endif 162 }; 163 164 /* 165 * 80387 control and status word bits 166 * 167 * The only reference I can find to bits 0x40 and 0x80 in the control word 168 * is for the Weitek 1167/3167. 169 * I (dsl) can't find why the default word has 0x40 set. 170 * 171 * A stack error is signalled as an INVOP that also sets STACK_FAULT 172 * (other INVOP do not clear STACK_FAULT). 173 */ 174 /* Interrupt masks (set masks interrupt) and status bits */ 175 #define EN_SW_INVOP 0x0001 /* Invalid operation */ 176 #define EN_SW_DENORM 0x0002 /* Denormalized operand */ 177 #define EN_SW_ZERODIV 0x0004 /* Divide by zero */ 178 #define EN_SW_OVERFLOW 0x0008 /* Overflow */ 179 #define EN_SW_UNDERFLOW 0x0010 /* Underflow */ 180 #define EN_SW_PRECLOSS 0x0020 /* Loss of precision */ 181 /* Status word bits (reserved in control word) */ 182 #define EN_SW_STACK_FAULT 0x0040 /* Stack under/overflow */ 183 #define EN_SW_ERROR_SUMMARY 0x0080 /* Unmasked error has occurred */ 184 /* Control bits (badly named) */ 185 #define EN_SW_CTL_PREC 0x0300 /* Precision control */ 186 #define EN_SW_PREC_24 0x0000 /* Single precision */ 187 #define EN_SW_PREC_53 0x0200 /* Double precision */ 188 #define EN_SW_PREC_64 0x0300 /* Extended precision */ 189 #define EN_SW_CTL_ROUND 0x0c00 /* Rounding control */ 190 #define EN_SW_ROUND_EVEN 0x0000 /* Round to nearest even */ 191 #define EN_SW_ROUND_DOWN 0x0400 /* Round towards minus infinity */ 192 #define EN_SW_ROUND_UP 0x0800 /* Round towards plus infinity */ 193 #define EN_SW_ROUND_ZERO 0x0c00 /* Round towards zero (truncates) */ 194 #define EN_SW_CTL_INF 0x1000 /* Infinity control, not used */ 195 196 /* 197 * The standard 0x87 control word from finit is 0x37F, giving: 198 * round to nearest 199 * 64-bit precision 200 * all exceptions masked. 201 * 202 * NetBSD used to select: 203 * round to nearest 204 * 53-bit precision 205 * all exceptions masked. 206 * Stating: 64-bit precision often gives bad results with high level 207 * languages because it makes the results of calculations depend on whether 208 * intermediate values are stored in memory or in FPU registers. 209 * Also some 'pathological divisions' give an error in the LSB because 210 * the value is first rounded up when the 64bit mantissa is generated, 211 * and then again when it is truncated to 53 bits. 212 * 213 * However the C language explicitly allows the extra precision. 214 * 215 * The iBCS control word has underflow, overflow, zero divide, and invalid 216 * operation exceptions unmasked. But that causes an unexpected exception 217 * in the test program 'paranoia' and makes denormals useless (DBL_MIN / 2 218 * underflows). It doesn't make a lot of sense to trap underflow without 219 * trapping denormals. 220 */ 221 #define __INITIAL_NPXCW__ 0x037f 222 /* Modern NetBSD uses the default control word.. */ 223 #define __NetBSD_NPXCW__ __INITIAL_NPXCW__ 224 /* NetBSD before 6.99.26 forced IEEE double precision. */ 225 #define __NetBSD_COMPAT_NPXCW__ 0x127f 226 /* FreeBSD leaves some exceptions unmasked as well. */ 227 #define __FreeBSD_NPXCW__ 0x1272 228 /* iBCS2 goes a bit further and leaves the underflow exception unmasked. */ 229 #define __iBCS2_NPXCW__ 0x0262 230 /* Linux just uses the default control word. */ 231 #define __Linux_NPXCW__ __INITIAL_NPXCW__ 232 /* SVR4 uses the same control word as iBCS2. */ 233 #define __SVR4_NPXCW__ 0x0262 234 235 /* 236 * The default MXCSR value at reset is 0x1f80, IA-32 Instruction 237 * Set Reference, pg. 3-369. 238 * 239 * The low 6 bits of the mxcsr are the fp status bits (same order as x87). 240 * Bit 6 is 'denormals are zero' (speeds up calculations). 241 * Bits 7-16 are the interrupt mask bits (same order, 1 to mask). 242 * Bits 13 and 14 are rounding control. 243 * Bit 15 is 'flush to zero' - affects underflow. 244 * Bits 16-31 must be zero. 245 */ 246 #define __INITIAL_MXCSR__ 0x1f80 247 #define __INITIAL_MXCSR_MASK__ 0xffbf 248 249 #endif /* _X86_CPU_EXTENDED_STATE_H_ */ 250