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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build darwin openbsd,amd64 openbsd,arm64
package runtime
import "unsafe"
// Call fn with arg as its argument. Return what fn returns.
// fn is the raw pc value of the entry point of the desired function.
// Switches to the system stack, if not already there.
// Preserves the calling point as the location where a profiler traceback will begin.
//go:nosplit
func libcCall(fn, arg unsafe.Pointer) int32 {
// Leave caller's PC/SP/G around for traceback.
gp := getg()
var mp *m
if gp != nil {
mp = gp.m
}
if mp != nil && mp.libcallsp == 0 {
mp.libcallg.set(gp)
mp.libcallpc = getcallerpc()
// sp must be the last, because once async cpu profiler finds
// all three values to be non-zero, it will use them
mp.libcallsp = getcallersp()
} else {
// Make sure we don't reset libcallsp. This makes
// libcCall reentrant; We remember the g/pc/sp for the
// first call on an M, until that libcCall instance
// returns. Reentrance only matters for signals, as
// libc never calls back into Go. The tricky case is
// where we call libcX from an M and record g/pc/sp.
// Before that call returns, a signal arrives on the
// same M and the signal handling code calls another
// libc function. We don't want that second libcCall
// from within the handler to be recorded, and we
// don't want that call's completion to zero
// libcallsp.
// We don't need to set libcall* while we're in a sighandler
// (even if we're not currently in libc) because we block all
// signals while we're handling a signal. That includes the
// profile signal, which is the one that uses the libcall* info.
mp = nil
}
res := asmcgocall(fn, arg)
if mp != nil {
mp.libcallsp = 0
}
return res
}
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