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Diffstat (limited to 'src/runtime/stack2.go')
| -rw-r--r-- | src/runtime/stack2.go | 106 |
1 files changed, 0 insertions, 106 deletions
diff --git a/src/runtime/stack2.go b/src/runtime/stack2.go deleted file mode 100644 index 5ec8d8d060..0000000000 --- a/src/runtime/stack2.go +++ /dev/null @@ -1,106 +0,0 @@ -// Copyright 2011 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 runtime - -/* -Stack layout parameters. -Included both by runtime (compiled via 6c) and linkers (compiled via gcc). - -The per-goroutine g->stackguard is set to point StackGuard bytes -above the bottom of the stack. Each function compares its stack -pointer against g->stackguard to check for overflow. To cut one -instruction from the check sequence for functions with tiny frames, -the stack is allowed to protrude StackSmall bytes below the stack -guard. Functions with large frames don't bother with the check and -always call morestack. The sequences are (for amd64, others are -similar): - - guard = g->stackguard - frame = function's stack frame size - argsize = size of function arguments (call + return) - - stack frame size <= StackSmall: - CMPQ guard, SP - JHI 3(PC) - MOVQ m->morearg, $(argsize << 32) - CALL morestack(SB) - - stack frame size > StackSmall but < StackBig - LEAQ (frame-StackSmall)(SP), R0 - CMPQ guard, R0 - JHI 3(PC) - MOVQ m->morearg, $(argsize << 32) - CALL morestack(SB) - - stack frame size >= StackBig: - MOVQ m->morearg, $((argsize << 32) | frame) - CALL morestack(SB) - -The bottom StackGuard - StackSmall bytes are important: there has -to be enough room to execute functions that refuse to check for -stack overflow, either because they need to be adjacent to the -actual caller's frame (deferproc) or because they handle the imminent -stack overflow (morestack). - -For example, deferproc might call malloc, which does one of the -above checks (without allocating a full frame), which might trigger -a call to morestack. This sequence needs to fit in the bottom -section of the stack. On amd64, morestack's frame is 40 bytes, and -deferproc's frame is 56 bytes. That fits well within the -StackGuard - StackSmall bytes at the bottom. -The linkers explore all possible call traces involving non-splitting -functions to make sure that this limit cannot be violated. -*/ - -const ( - // StackSystem is a number of additional bytes to add - // to each stack below the usual guard area for OS-specific - // purposes like signal handling. Used on Windows, Plan 9, - // and Darwin/ARM because they do not use a separate stack. - _StackSystem = goos_windows*512*ptrSize + goos_plan9*512 + goos_darwin*goarch_arm*1024 - - // The minimum size of stack used by Go code - _StackMin = 2048 - - // The minimum stack size to allocate. - // The hackery here rounds FixedStack0 up to a power of 2. - _FixedStack0 = _StackMin + _StackSystem - _FixedStack1 = _FixedStack0 - 1 - _FixedStack2 = _FixedStack1 | (_FixedStack1 >> 1) - _FixedStack3 = _FixedStack2 | (_FixedStack2 >> 2) - _FixedStack4 = _FixedStack3 | (_FixedStack3 >> 4) - _FixedStack5 = _FixedStack4 | (_FixedStack4 >> 8) - _FixedStack6 = _FixedStack5 | (_FixedStack5 >> 16) - _FixedStack = _FixedStack6 + 1 - - // Functions that need frames bigger than this use an extra - // instruction to do the stack split check, to avoid overflow - // in case SP - framesize wraps below zero. - // This value can be no bigger than the size of the unmapped - // space at zero. - _StackBig = 4096 - - // The stack guard is a pointer this many bytes above the - // bottom of the stack. - _StackGuard = 640*stackGuardMultiplier + _StackSystem - - // After a stack split check the SP is allowed to be this - // many bytes below the stack guard. This saves an instruction - // in the checking sequence for tiny frames. - _StackSmall = 128 - - // The maximum number of bytes that a chain of NOSPLIT - // functions can use. - _StackLimit = _StackGuard - _StackSystem - _StackSmall -) - -// Goroutine preemption request. -// Stored into g->stackguard0 to cause split stack check failure. -// Must be greater than any real sp. -// 0xfffffade in hex. -const ( - _StackPreempt = uintptrMask & -1314 - _StackFork = uintptrMask & -1234 -) |