Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/src/internal/abi/stack.go b/src/internal/abi/stack.go
new file mode 100644
index 0000000..8e3327e
--- /dev/null
+++ b/src/internal/abi/stack.go
@@ -0,0 +1,33 @@
+// Copyright 2023 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.
+
+package abi
+
+const (
+	// StackNosplitBase is the base maximum number of bytes that a chain of
+	// NOSPLIT functions can use.
+	//
+	// This value must be multiplied by the stack guard multiplier, so do not
+	// use it directly. See runtime/stack.go:stackNosplit and
+	// cmd/internal/objabi/stack.go:StackNosplit.
+	StackNosplitBase = 800
+
+	// We have three different sequences for stack bounds checks, depending on
+	// whether the stack frame of a function is small, big, or huge.
+
+	// After a stack split check the SP is allowed to be StackSmall bytes below
+	// the stack guard.
+	//
+	// Functions that need frames <= StackSmall can perform the stack check
+	// using a single comparison directly between the stack guard and the SP
+	// because we ensure that StackSmall bytes of stack space are available
+	// beyond the stack guard.
+	StackSmall = 128
+
+	// Functions that need frames <= StackBig can assume that neither
+	// SP-framesize nor stackGuard-StackSmall will underflow, and thus use a
+	// more efficient check. In order to ensure this, StackBig must be <= the
+	// size of the unmapped space at zero.
+	StackBig = 4096
+)