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https://github.com/golang/go
synced 2024-11-22 02:14:40 -07:00
runtime: prefer fixed stack allocator over general memory allocator
* move stack constants from proc.c to runtime.h * make memclr take uintptr length R=r CC=golang-dev https://golang.org/cl/3985046
This commit is contained in:
Russ Cox
parent
eaae95fa3d
commit
afc6928ad9
@ -407,9 +407,9 @@ TEXT runtime·stackcheck(SB), 7, $0
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TEXT runtime·memclr(SB),7,$0
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MOVQ 8(SP), DI // arg 1 addr
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MOVL 16(SP), CX // arg 2 count
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ADDL $7, CX
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SHRL $3, CX
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MOVQ 16(SP), CX // arg 2 count
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ADDQ $7, CX
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SHRQ $3, CX
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MOVQ $0, AX
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CLD
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REP
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@ -282,13 +282,17 @@ static struct {
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FixAlloc;
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} stacks;
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enum {
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FixedStack = StackBig + StackExtra
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};
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void*
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runtime·stackalloc(uint32 n)
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{
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void *v;
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uint32 *ref;
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if(m->mallocing || m->gcing) {
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if(m->mallocing || m->gcing || n == FixedStack) {
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runtime·lock(&stacks);
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if(stacks.size == 0)
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runtime·FixAlloc_Init(&stacks, n, runtime·SysAlloc, nil, nil);
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@ -310,9 +314,9 @@ runtime·stackalloc(uint32 n)
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}
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void
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runtime·stackfree(void *v)
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runtime·stackfree(void *v, uintptr n)
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{
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if(m->mallocing || m->gcing) {
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if(m->mallocing || m->gcing || n == FixedStack) {
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runtime·lock(&stacks);
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runtime·FixAlloc_Free(&stacks, v);
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mstats.stacks_inuse = stacks.inuse;
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@ -678,87 +678,6 @@ runtime·endcgocallback(G* g1)
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runtime·free(d);
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}
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/*
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* stack layout parameters.
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* known to linkers.
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*
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* g->stackguard is set to point StackGuard bytes
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* above the bottom of the stack. each function
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* compares its stack pointer against g->stackguard
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* to check for overflow. to cut one instruction from
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* the check sequence for functions with tiny frames,
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* the stack is allowed to protrude StackSmall bytes
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* below the stack guard. functions with large frames
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* don't bother with the check and always call morestack.
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* the sequences are (for amd64, others are similar):
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*
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* guard = g->stackguard
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* frame = function's stack frame size
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* argsize = size of function arguments (call + return)
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*
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* stack frame size <= StackSmall:
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* CMPQ guard, SP
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* JHI 3(PC)
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* MOVQ m->morearg, $(argsize << 32)
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* CALL sys.morestack(SB)
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*
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* stack frame size > StackSmall but < StackBig
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* LEAQ (frame-StackSmall)(SP), R0
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* CMPQ guard, R0
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* JHI 3(PC)
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* MOVQ m->morearg, $(argsize << 32)
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* CALL sys.morestack(SB)
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*
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* stack frame size >= StackBig:
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* MOVQ m->morearg, $((argsize << 32) | frame)
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* CALL sys.morestack(SB)
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*
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* the bottom StackGuard - StackSmall bytes are important:
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* there has to be enough room to execute functions that
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* refuse to check for stack overflow, either because they
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* need to be adjacent to the actual caller's frame (sys.deferproc)
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* or because they handle the imminent stack overflow (sys.morestack).
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*
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* for example, sys.deferproc might call malloc,
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* which does one of the above checks (without allocating a full frame),
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* which might trigger a call to sys.morestack.
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* this sequence needs to fit in the bottom section of the stack.
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* on amd64, sys.morestack's frame is 40 bytes, and
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* sys.deferproc's frame is 56 bytes. that fits well within
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* the StackGuard - StackSmall = 128 bytes at the bottom.
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* there may be other sequences lurking or yet to be written
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* that require more stack. sys.morestack checks to make sure
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* the stack has not completely overflowed and should
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* catch such sequences.
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*/
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enum
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{
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#ifdef __WINDOWS__
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// need enough room in guard area for exception handler.
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// use larger stacks to compensate for larger stack guard.
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StackSmall = 256,
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StackGuard = 2048,
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StackBig = 8192,
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StackExtra = StackGuard,
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#else
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// byte offset of stack guard (g->stackguard) above bottom of stack.
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StackGuard = 256,
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// checked frames are allowed to protrude below the guard by
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// this many bytes. this saves an instruction in the checking
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// sequence when the stack frame is tiny.
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StackSmall = 128,
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// extra space in the frame (beyond the function for which
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// the frame is allocated) is assumed not to be much bigger
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// than this amount. it may not be used efficiently if it is.
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StackBig = 4096,
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// extra room over frame size when allocating a stack.
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StackExtra = 1024,
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#endif
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};
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void
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runtime·oldstack(void)
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{
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@ -781,8 +700,8 @@ runtime·oldstack(void)
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}
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goid = old.gobuf.g->goid; // fault if g is bad, before gogo
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if(old.free)
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runtime·stackfree(g1->stackguard - StackGuard);
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if(old.free != 0)
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runtime·stackfree(g1->stackguard - StackGuard, old.free);
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g1->stackbase = old.stackbase;
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g1->stackguard = old.stackguard;
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@ -797,7 +716,8 @@ runtime·newstack(void)
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byte *stk, *sp;
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G *g1;
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Gobuf label;
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bool free, reflectcall;
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bool reflectcall;
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uintptr free;
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framesize = m->moreframesize;
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argsize = m->moreargsize;
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@ -818,7 +738,7 @@ runtime·newstack(void)
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// we don't need to create a new segment.
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top = (Stktop*)(m->morebuf.sp - sizeof(*top));
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stk = g1->stackguard - StackGuard;
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free = false;
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free = 0;
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} else {
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// allocate new segment.
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framesize += argsize;
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@ -827,7 +747,7 @@ runtime·newstack(void)
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framesize += StackExtra; // room for more functions, Stktop.
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stk = runtime·stackalloc(framesize);
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top = (Stktop*)(stk+framesize-sizeof(*top));
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free = true;
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free = framesize;
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}
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//printf("newstack frame=%d args=%d morepc=%p morefp=%p gobuf=%p, %p newstk=%p\n",
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@ -1036,8 +956,8 @@ unwindstack(G *gp, byte *sp)
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break;
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gp->stackbase = top->stackbase;
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gp->stackguard = top->stackguard;
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if(top->free)
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runtime·stackfree(stk);
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if(top->free != 0)
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runtime·stackfree(stk, top->free);
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}
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if(sp != nil && (sp < gp->stackguard - StackGuard || gp->stackbase < sp)) {
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@ -84,6 +84,10 @@ runtime·panicstring(int8 *s)
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{
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Eface err;
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if(m->gcing) {
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runtime·printf("panic: %s\n", s);
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runtime·throw("panic during gc");
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}
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runtime·newErrorString(runtime·gostringnocopy((byte*)s), &err);
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runtime·panic(err);
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}
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@ -247,7 +247,7 @@ struct Stktop
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uint32 argsize;
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uint8* argp; // pointer to arguments in old frame
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bool free; // call stackfree for this frame?
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uintptr free; // if free>0, call stackfree using free as size
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bool panic; // is this frame the top of a panic?
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};
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struct Alg
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@ -421,7 +421,7 @@ void runtime·minit(void);
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Func* runtime·findfunc(uintptr);
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int32 runtime·funcline(Func*, uint64);
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void* runtime·stackalloc(uint32);
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void runtime·stackfree(void*);
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void runtime·stackfree(void*, uintptr);
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MCache* runtime·allocmcache(void);
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void runtime·mallocinit(void);
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bool runtime·ifaceeq_c(Iface, Iface);
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@ -506,11 +506,11 @@ void runtime·notewakeup(Note*);
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#define EACCES 13
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/*
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* low level go-called
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* low level C-called
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*/
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uint8* runtime·mmap(byte*, uintptr, int32, int32, int32, uint32);
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void runtime·munmap(uint8*, uintptr);
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void runtime·memclr(byte*, uint32);
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void runtime·memclr(byte*, uintptr);
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void runtime·setcallerpc(void*, void*);
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void* runtime·getcallerpc(void*);
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@ -588,3 +588,84 @@ int32 runtime·chanlen(Hchan*);
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int32 runtime·chancap(Hchan*);
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void runtime·ifaceE2I(struct InterfaceType*, Eface, Iface*);
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/*
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* Stack layout parameters.
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* Known to linkers.
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*
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* The per-goroutine g->stackguard is set to point
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* StackGuard bytes above the bottom of the stack.
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* Each function compares its stack pointer against
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* g->stackguard to check for overflow. To cut one
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* instruction from the check sequence for functions
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* with tiny frames, the stack is allowed to protrude
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* StackSmall bytes below the stack guard. Functions
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* with large frames don't bother with the check and
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* always call morestack. The sequences are
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* (for amd64, others are similar):
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*
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* guard = g->stackguard
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* frame = function's stack frame size
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* argsize = size of function arguments (call + return)
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*
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* stack frame size <= StackSmall:
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* CMPQ guard, SP
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* JHI 3(PC)
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* MOVQ m->morearg, $(argsize << 32)
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* CALL morestack(SB)
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*
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* stack frame size > StackSmall but < StackBig
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* LEAQ (frame-StackSmall)(SP), R0
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* CMPQ guard, R0
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* JHI 3(PC)
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* MOVQ m->morearg, $(argsize << 32)
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* CALL morestack(SB)
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*
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* stack frame size >= StackBig:
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* MOVQ m->morearg, $((argsize << 32) | frame)
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* CALL morestack(SB)
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*
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* The bottom StackGuard - StackSmall bytes are important:
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* there has to be enough room to execute functions that
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* refuse to check for stack overflow, either because they
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* need to be adjacent to the actual caller's frame (deferproc)
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* or because they handle the imminent stack overflow (morestack).
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*
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* For example, deferproc might call malloc, which does one
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* of the above checks (without allocating a full frame),
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* which might trigger a call to morestack. This sequence
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* needs to fit in the bottom section of the stack. On amd64,
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* morestack's frame is 40 bytes, and deferproc's frame is 56 bytes.
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* That fits well within the StackGuard - StackSmall = 128 bytes
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* at the bottom. There may be other sequences lurking or yet to
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* be written that require more stack. Morestack checks to make
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* sure the stack has not completely overflowed and should catch
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* such sequences.
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*/
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enum
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{
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#ifdef __WINDOWS__
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// need enough room in guard area for exception handler.
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// use larger stacks to compensate for larger stack guard.
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StackSmall = 256,
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StackGuard = 2048,
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StackBig = 8192,
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StackExtra = StackGuard,
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#else
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// byte offset of stack guard (g->stackguard) above bottom of stack.
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StackGuard = 256,
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// checked frames are allowed to protrude below the guard by
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// this many bytes. this saves an instruction in the checking
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// sequence when the stack frame is tiny.
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StackSmall = 128,
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// extra space in the frame (beyond the function for which
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// the frame is allocated) is assumed not to be much bigger
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// than this amount. it may not be used efficiently if it is.
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StackBig = 4096,
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// extra room over frame size when allocating a stack.
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StackExtra = 1024,
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#endif
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};
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