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24ec1754b2
the maximum size of the Xsave area was previously hardcoded but the CPUID instruction can be used to determine its maximum size.
31 lines
755 B
Go
31 lines
755 B
Go
package amd64util
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import (
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"sync"
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)
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var xstateMaxSize int
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var loadXstateMaxSizeOnce sync.Once
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func cpuid(axIn, cxIn uint32) (axOut, bxOut, cxOut, dxOut uint32)
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func AMD64XstateMaxSize() int {
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loadXstateMaxSizeOnce.Do(func() {
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// See Intel 64 and IA-32 Architecture Software Developer's Manual, Vol. 1
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// chapter 13.2 and Vol. 2A CPUID instruction for a description of all the
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// magic constants.
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_, _, cx, _ := cpuid(0x01, 0x00)
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if cx&(1<<26) == 0 { // Vol. 2A, Table 3-10, XSAVE enabled bit check
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// XSAVE not supported by this processor
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xstateMaxSize = _XSTATE_MAX_KNOWN_SIZE
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return
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}
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_, _, cx, _ = cpuid(0x0d, 0x00) // processor extended state enumeration main leaf
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xstateMaxSize = int(cx)
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})
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return xstateMaxSize
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}
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