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runtime: assume precisestack, copystack, StackCopyAlways, ScanStackBy…
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…Frames

Commit to stack copying for stack growth.

We're carrying around a surprising amount of cruft from older schemes.
I am confident that precise stack scans and stack copying are here to stay.

Delete fallback code for when precise stack info is disabled.
Delete fallback code for when copying stacks is disabled.
Delete fallback code for when StackCopyAlways is disabled.
Delete Stktop chain - there is only one stack segment now.
Delete M.moreargp, M.moreargsize, M.moreframesize, M.cret.
Delete G.writenbuf (unrelated, just dead).
Delete runtime.lessstack, runtime.oldstack.
Delete many amd64 morestack variants.
Delete initialization of morestack frame/arg sizes (shortens split prologue!).

Replace G's stackguard/stackbase/stack0/stacksize/
syscallstack/syscallguard/forkstackguard with simple stack
bounds (lo, hi).

Update liblink, runtime/cgo for adjustments to G.

LGTM=khr
R=khr, bradfitz
CC=golang-codereviews, iant, r
https://golang.org/cl/137410043
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rsc committed Sep 9, 2014
1 parent d72029e commit 15b76ad
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Showing 50 changed files with 359 additions and 2,894 deletions.
2 changes: 1 addition & 1 deletion include/link.h
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Original file line number Diff line number Diff line change
Expand Up @@ -392,7 +392,7 @@ struct Link
LSym* sym_divu;
LSym* sym_mod;
LSym* sym_modu;
LSym* symmorestack[20];
LSym* symmorestack[2];
LSym* tlsg;
LSym* plan9privates;
Prog* curp;
Expand Down
2 changes: 2 additions & 0 deletions src/cmd/dist/buildruntime.c
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Original file line number Diff line number Diff line change
Expand Up @@ -246,6 +246,8 @@ mkzasm(char *dir, char *file)
aggr = "alg";
else if(streq(fields.p[1], "Panic"))
aggr = "panic";
else if(streq(fields.p[1], "Stack"))
aggr = "stack";
}
if(hasprefix(lines.p[i], "}"))
aggr = nil;
Expand Down
30 changes: 3 additions & 27 deletions src/liblink/obj5.c
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Original file line number Diff line number Diff line change
Expand Up @@ -458,7 +458,7 @@ addstacksplit(Link *ctxt, LSym *cursym)
p->as = AMOVW;
p->from.type = D_OREG;
p->from.reg = REGG;
p->from.offset = 2*ctxt->arch->ptrsize; // G.panic
p->from.offset = 4*ctxt->arch->ptrsize; // G.panic
p->to.type = D_REG;
p->to.reg = 1;

Expand Down Expand Up @@ -762,15 +762,14 @@ softfloat(Link *ctxt, LSym *cursym)
static Prog*
stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt)
{
int32 arg;

// MOVW g_stackguard(g), R1
p = appendp(ctxt, p);
p->as = AMOVW;
p->from.type = D_OREG;
p->from.reg = REGG;
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->from.offset = 3*ctxt->arch->ptrsize;
p->from.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
p->to.type = D_REG;
p->to.reg = 1;

Expand Down Expand Up @@ -849,29 +848,6 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt)
p->scond = C_SCOND_NE;
}

// MOVW.LS $framesize, R1
p = appendp(ctxt, p);
p->as = AMOVW;
p->scond = C_SCOND_LS;
p->from.type = D_CONST;
p->from.offset = framesize;
p->to.type = D_REG;
p->to.reg = 1;

// MOVW.LS $args, R2
p = appendp(ctxt, p);
p->as = AMOVW;
p->scond = C_SCOND_LS;
p->from.type = D_CONST;
arg = ctxt->cursym->text->to.offset2;
if(arg == 1) // special marker for known 0
arg = 0;
if(arg&3)
ctxt->diag("misaligned argument size in stack split");
p->from.offset = arg;
p->to.type = D_REG;
p->to.reg = 2;

// MOVW.LS R14, R3
p = appendp(ctxt, p);
p->as = AMOVW;
Expand Down
186 changes: 16 additions & 170 deletions src/liblink/obj6.c
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Original file line number Diff line number Diff line change
Expand Up @@ -342,32 +342,6 @@ nacladdr(Link *ctxt, Prog *p, Addr *a)
}
}

static char*
morename[] =
{
"runtime.morestack00",
"runtime.morestack00_noctxt",
"runtime.morestack10",
"runtime.morestack10_noctxt",
"runtime.morestack01",
"runtime.morestack01_noctxt",
"runtime.morestack11",
"runtime.morestack11_noctxt",

"runtime.morestack8",
"runtime.morestack8_noctxt",
"runtime.morestack16",
"runtime.morestack16_noctxt",
"runtime.morestack24",
"runtime.morestack24_noctxt",
"runtime.morestack32",
"runtime.morestack32_noctxt",
"runtime.morestack40",
"runtime.morestack40_noctxt",
"runtime.morestack48",
"runtime.morestack48_noctxt",
};

static Prog* load_g_cx(Link*, Prog*);
static Prog* stacksplit(Link*, Prog*, int32, int32, int, Prog**);
static void indir_cx(Link*, Addr*);
Expand All @@ -388,19 +362,16 @@ parsetextconst(vlong arg, vlong *textstksiz, vlong *textarg)
static void
addstacksplit(Link *ctxt, LSym *cursym)
{
Prog *p, *q, *q1, *p1, *p2;
Prog *p, *q, *p1, *p2;
int32 autoffset, deltasp;
int a, pcsize;
uint32 i;
vlong textstksiz, textarg;

if(ctxt->tlsg == nil)
ctxt->tlsg = linklookup(ctxt, "runtime.tlsg", 0);
if(ctxt->symmorestack[0] == nil) {
if(nelem(morename) > nelem(ctxt->symmorestack))
sysfatal("Link.symmorestack needs at least %d elements", nelem(morename));
for(i=0; i<nelem(morename); i++)
ctxt->symmorestack[i] = linklookup(ctxt, morename[i], 0);
ctxt->symmorestack[0] = linklookup(ctxt, "runtime.morestack", 0);
ctxt->symmorestack[1] = linklookup(ctxt, "runtime.morestack_noctxt", 0);
}

if(ctxt->headtype == Hplan9 && ctxt->plan9privates == nil)
Expand Down Expand Up @@ -481,7 +452,7 @@ addstacksplit(Link *ctxt, LSym *cursym)
p = appendp(ctxt, p);
p->as = AMOVQ;
p->from.type = D_INDIR+D_CX;
p->from.offset = 2*ctxt->arch->ptrsize; // G.panic
p->from.offset = 4*ctxt->arch->ptrsize; // G.panic
p->to.type = D_BX;
if(ctxt->headtype == Hnacl) {
p->as = AMOVL;
Expand Down Expand Up @@ -545,42 +516,6 @@ addstacksplit(Link *ctxt, LSym *cursym)
p2->pcond = p;
}

if(ctxt->debugstack > 1 && autoffset) {
// 6l -K -K means double-check for stack overflow
// even after calling morestack and even if the
// function is marked as nosplit.
p = appendp(ctxt, p);
p->as = AMOVQ;
indir_cx(ctxt, &p->from);
p->from.offset = 0;
p->to.type = D_BX;

p = appendp(ctxt, p);
p->as = ASUBQ;
p->from.type = D_CONST;
p->from.offset = StackSmall+32;
p->to.type = D_BX;

p = appendp(ctxt, p);
p->as = ACMPQ;
p->from.type = D_SP;
p->to.type = D_BX;

p = appendp(ctxt, p);
p->as = AJHI;
p->to.type = D_BRANCH;
q1 = p;

p = appendp(ctxt, p);
p->as = AINT;
p->from.type = D_CONST;
p->from.offset = 3;

p = appendp(ctxt, p);
p->as = ANOP;
q1->pcond = p;
}

if(ctxt->debugzerostack && autoffset && !(cursym->text->from.scale&NOSPLIT)) {
// 6l -Z means zero the stack frame on entry.
// This slows down function calls but can help avoid
Expand Down Expand Up @@ -731,9 +666,9 @@ static Prog*
stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog **jmpok)
{
Prog *q, *q1;
uint32 moreconst1, moreconst2, i;
int cmp, lea, mov, sub;

USED(textarg);
cmp = ACMPQ;
lea = ALEAQ;
mov = AMOVQ;
Expand All @@ -746,35 +681,6 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
sub = ASUBL;
}

if(ctxt->debugstack) {
// 6l -K means check not only for stack
// overflow but stack underflow.
// On underflow, INT 3 (breakpoint).
// Underflow itself is rare but this also
// catches out-of-sync stack guard info

p = appendp(ctxt, p);
p->as = cmp;
indir_cx(ctxt, &p->from);
p->from.offset = 8;
p->to.type = D_SP;

p = appendp(ctxt, p);
p->as = AJHI;
p->to.type = D_BRANCH;
p->to.offset = 4;
q1 = p;

p = appendp(ctxt, p);
p->as = AINT;
p->from.type = D_CONST;
p->from.offset = 3;

p = appendp(ctxt, p);
p->as = ANOP;
q1->pcond = p;
}

q1 = nil;
if(framesize <= StackSmall) {
// small stack: SP <= stackguard
Expand All @@ -783,8 +689,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p->as = cmp;
p->from.type = D_SP;
indir_cx(ctxt, &p->to);
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->to.offset = 3*ctxt->arch->ptrsize;
p->to.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
} else if(framesize <= StackBig) {
// large stack: SP-framesize <= stackguard-StackSmall
// LEAQ -xxx(SP), AX
Expand All @@ -799,8 +706,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p->as = cmp;
p->from.type = D_AX;
indir_cx(ctxt, &p->to);
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->to.offset = 3*ctxt->arch->ptrsize;
p->to.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
} else {
// Such a large stack we need to protect against wraparound.
// If SP is close to zero:
Expand All @@ -820,9 +728,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p = appendp(ctxt, p);
p->as = mov;
indir_cx(ctxt, &p->from);
p->from.offset = 0;
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->from.offset = 3*ctxt->arch->ptrsize;
p->from.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
p->to.type = D_SI;

p = appendp(ctxt, p);
Expand Down Expand Up @@ -860,75 +768,13 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p->to.type = D_BRANCH;
q = p;

// If we ask for more stack, we'll get a minimum of StackMin bytes.
// We need a stack frame large enough to hold the top-of-stack data,
// the function arguments+results, our caller's PC, our frame,
// a word for the return PC of the next call, and then the StackLimit bytes
// that must be available on entry to any function called from a function
// that did a stack check. If StackMin is enough, don't ask for a specific
// amount: then we can use the custom functions and save a few
// instructions.
moreconst1 = 0;
if(StackTop + textarg + ctxt->arch->ptrsize + framesize + ctxt->arch->ptrsize + StackLimit >= StackMin)
moreconst1 = framesize;
moreconst2 = textarg;
if(moreconst2 == 1) // special marker
moreconst2 = 0;
if((moreconst2&7) != 0)
ctxt->diag("misaligned argument size in stack split");
// 4 varieties varieties (const1==0 cross const2==0)
// and 6 subvarieties of (const1==0 and const2!=0)
p = appendp(ctxt, p);
if(ctxt->cursym->cfunc) {
p->as = ACALL;
p->to.type = D_BRANCH;
p->as = ACALL;
p->to.type = D_BRANCH;
if(ctxt->cursym->cfunc)
p->to.sym = linklookup(ctxt, "runtime.morestackc", 0);
} else
if(moreconst1 == 0 && moreconst2 == 0) {
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[0*2+noctxt];
} else
if(moreconst1 != 0 && moreconst2 == 0) {
p->as = AMOVL;
p->from.type = D_CONST;
p->from.offset = moreconst1;
p->to.type = D_AX;

p = appendp(ctxt, p);
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[1*2+noctxt];
} else
if(moreconst1 == 0 && moreconst2 <= 48 && moreconst2%8 == 0) {
i = moreconst2/8 + 3;
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[i*2+noctxt];
} else
if(moreconst1 == 0 && moreconst2 != 0) {
p->as = AMOVL;
p->from.type = D_CONST;
p->from.offset = moreconst2;
p->to.type = D_AX;

p = appendp(ctxt, p);
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[2*2+noctxt];
} else {
// Pass framesize and argsize.
p->as = AMOVQ;
p->from.type = D_CONST;
p->from.offset = (uint64)moreconst2 << 32;
p->from.offset |= moreconst1;
p->to.type = D_AX;

p = appendp(ctxt, p);
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[3*2+noctxt];
}
else
p->to.sym = ctxt->symmorestack[noctxt];

p = appendp(ctxt, p);
p->as = AJMP;
Expand Down
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