41 lines
1.5 KiB
Go
41 lines
1.5 KiB
Go
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// SPDX-License-Identifier: Apache-2.0
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// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
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//go:build darwin || freebsd || linux || windows
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package purego
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const (
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maxArgs = 9
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numOfFloats = 8 // arm64 and amd64 both have 8 float registers
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)
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// SyscallN takes fn, a C function pointer and a list of arguments as uintptr.
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// There is an internal maximum number of arguments that SyscallN can take. It panics
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// when the maximum is exceeded. It returns the result and the libc error code if there is one.
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//
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// NOTE: SyscallN does not properly call functions that have both integer and float parameters.
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// See discussion comment https://github.com/ebiten/purego/pull/1#issuecomment-1128057607
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// for an explanation of why that is.
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//
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// On amd64, if there are more than 8 floats the 9th and so on will be placed incorrectly on the
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// stack.
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//
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// The pragma go:nosplit is not needed at this function declaration because it uses go:uintptrescapes
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// which forces all the objects that the uintptrs point to onto the heap where a stack split won't affect
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// their memory location.
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//
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//go:uintptrescapes
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func SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
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if fn == 0 {
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panic("purego: fn is nil")
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}
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if len(args) > maxArgs {
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panic("purego: too many arguments to SyscallN")
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}
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// add padding so there is no out-of-bounds slicing
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var tmp [maxArgs]uintptr
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copy(tmp[:], args)
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return syscall_syscall9X(fn, tmp[0], tmp[1], tmp[2], tmp[3], tmp[4], tmp[5], tmp[6], tmp[7], tmp[8])
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}
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