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Diffstat (limited to 'src/pkg/runtime/stack.h')
-rw-r--r-- | src/pkg/runtime/stack.h | 96 |
1 files changed, 0 insertions, 96 deletions
diff --git a/src/pkg/runtime/stack.h b/src/pkg/runtime/stack.h deleted file mode 100644 index 2b6b0e387..000000000 --- a/src/pkg/runtime/stack.h +++ /dev/null @@ -1,96 +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. - -/* -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 = 128 bytes at the bottom. -The linkers explore all possible call traces involving non-splitting -functions to make sure that this limit cannot be violated. - */ - -enum { - // 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 because - // it does not use a separate stack. -#ifdef __WINDOWS__ - StackSystem = 2048, -#else - StackSystem = 0, -#endif - - // The amount of extra stack to allocate beyond the size - // needed for the single frame that triggered the split. - StackExtra = 1024, - - // The minimum stack segment size to allocate. - // If the amount needed for the splitting frame + StackExtra - // is less than this number, the stack will have this size instead. - StackMin = 4096, - - // Functions that need frames bigger than this call morestack - // unconditionally. That is, on entry to a function it is assumed - // that the amount of space available in the current stack segment - // couldn't possibly be bigger than StackBig. If stack segments - // do run with more space than StackBig, the space may not be - // used efficiently. As a result, StackBig should not be significantly - // smaller than StackMin or StackExtra. - StackBig = 4096, - - // The stack guard is a pointer this many bytes above the - // bottom of the stack. - StackGuard = 256 + 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, -}; |