| Index: src/pkg/runtime/runtime.h |
| =================================================================== |
| --- a/src/pkg/runtime/runtime.h |
| +++ b/src/pkg/runtime/runtime.h |
| @@ -592,83 +592,17 @@ |
| void runtime·ifaceE2I(struct InterfaceType*, Eface, Iface*); |
| -/* |
| - * Stack layout parameters. |
| - * Known to linkers. |
| - * |
| - * 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. There may be other sequences lurking or yet to |
| - * be written that require more stack. Morestack checks to make |
| - * sure the stack has not completely overflowed and should catch |
| - * such sequences. |
| - */ |
| 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. |
| + // TODO(rsc): This is only for Windows. Can't Windows use |
| + // a separate exception stack like every other operating system? |
| #ifdef __WINDOWS__ |
| - // need enough room in guard area for exception handler. |
| - // use larger stacks to compensate for larger stack guard. |
| - StackSmall = 256, |
| - StackGuard = 2048, |
| - StackBig = 8192, |
| - StackExtra = StackGuard, |
| + StackSystem = 2048, |
| #else |
| - // byte offset of stack guard (g->stackguard) above bottom of stack. |
| - StackGuard = 256, |
| - |
| - // checked frames are allowed to protrude below the guard by |
| - // this many bytes. this saves an instruction in the checking |
| - // sequence when the stack frame is tiny. |
| - StackSmall = 128, |
| - |
| - // extra space in the frame (beyond the function for which |
| - // the frame is allocated) is assumed not to be much bigger |
| - // than this amount. it may not be used efficiently if it is. |
| - StackBig = 4096, |
| - |
| - // extra room over frame size when allocating a stack. |
| - StackExtra = 1024, |
| + StackSystem = 0, |
| #endif |
| }; |
| + |
