146 lines
2.7 KiB
C++
146 lines
2.7 KiB
C++
/*
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* \brief x86 FPU driver for core
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* \author Adrian-Ken Rueegsegger
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* \author Martin stein
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* \author Reto Buerki
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* \author Stefan Kalkowski
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* \date 2016-01-19
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*/
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/*
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* Copyright (C) 2016 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _SPEC__X86__FPU_H_
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#define _SPEC__X86__FPU_H_
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/* Genode includes */
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#include <base/stdint.h>
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namespace Genode { class Fpu; }
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class Genode::Fpu
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{
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public:
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class Context
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{
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private:
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friend class Fpu;
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/*
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* FXSAVE area providing storage for x87 FPU, MMX, XMM,
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* and MXCSR registers.
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*
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* For further details see Intel SDM Vol. 2A,
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* 'FXSAVE instruction'.
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*/
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char _fxsave_area[527];
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/* 16-byte aligned start of FXSAVE area. */
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char * _start = nullptr;
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Fpu * _fpu = nullptr;
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bool _init()
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{
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if (_start) return true;
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_start = ((addr_t)_fxsave_area & 15)
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? (char *)((addr_t)_fxsave_area & ~15) + 16
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: _fxsave_area;
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return false;
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}
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public:
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~Context() { if (_fpu) _fpu->unset(*this); }
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} __attribute__((aligned(16)));
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private:
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enum { MXCSR_DEFAULT = 0x1f80 };
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Context * _context = nullptr;
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/**
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* Reset FPU
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*
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* Doesn't check for pending unmasked floating-point
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* exceptions and explicitly sets the MXCSR to the
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* default value.
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*/
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void _reset()
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{
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unsigned value = MXCSR_DEFAULT;
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asm volatile ("fninit");
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asm volatile ("ldmxcsr %0" : : "m" (value));
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}
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/**
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* Load x87 FPU context
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*/
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void _load()
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{
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if (!_context->_init()) _reset();
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else asm volatile ("fxrstor %0" : : "m" (*_context->_start));
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}
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/**
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* Save x87 FPU context
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*/
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void _save() {
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asm volatile ("fxsave %0" : "=m" (*_context->_start)); }
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public:
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/**
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* Disable FPU by setting the TS flag in CR0.
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*/
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void disable();
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/**
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* Enable FPU by clearing the TS flag in CR0.
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*/
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void enable() { asm volatile ("clts"); }
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/**
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* Initialize all FPU-related CR flags
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*
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* Initialize FPU with SSE extensions by setting required CR0 and CR4
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* bits to configure the FPU environment according to Intel SDM Vol.
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* 3A, sections 9.2 and 9.6.
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*/
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void init();
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/**
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* Returns True if the FPU is enabled.
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*/
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bool enabled();
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/**
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* Switch to new context
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*
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* \param context next FPU context
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*/
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void switch_to(Context &context) {
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if (_context != &context) disable(); }
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/**
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* Return whether to retry an FPU instruction after this call
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*/
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bool fault(Context &context);
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/**
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* Unset FPU context
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*/
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void unset(Context &context) {
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if (_context == &context) _context = nullptr; }
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};
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#endif /* _SPEC__X86__FPU_H_ */
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