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add -K flag to check stack underflow

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R=ken
DELTA=38  (36 added, 0 deleted, 2 changed)
OCL=15482
CL=15491
This commit is contained in:
Russ Cox 2008-09-18 15:41:20 -07:00
parent d1d7dc6c42
commit f74ec00278
1 changed files with 38 additions and 2 deletions
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40
src/cmd/6l/pass.c
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@ -565,7 +565,7 @@ brloop(Prog *p)
void
dostkoff(void)
{
Prog *p, *q;
Prog *p, *q, *q1;
int32 autoffset, deltasp;
int a, f, curframe, curbecome, maxbecome, pcsize;
Prog *pmorestack;
@ -667,8 +667,33 @@ dostkoff(void)
autoffset = 0;
q = P;
q1 = P;
if(pmorestack != P)
if(!(p->from.scale & NOSPLIT)) {
if(debug['K']) {
// 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(p);
p->as = ACMPQ;
p->from.type = D_INDIR+D_R15;
p->from.offset = 8;
p->to.type = D_SP;
p = appendp(p);
p->as = AJHI;
p->to.type = D_BRANCH;
p->to.offset = 4;
q1 = p;
p = appendp(p);
p->as = AINT;
p->from.type = D_CONST;
p->from.offset = 3;
}
if(autoffset < 4096) { // do we need to call morestack
if(autoffset <= 75) {
// small stack
@ -676,7 +701,10 @@ dostkoff(void)
p->as = ACMPQ;
p->from.type = D_SP;
p->to.type = D_INDIR+D_R15;
if(q1) {
q1->pcond = p;
q1 = P;
}
} else {
// large stack
p = appendp(p);
@ -684,6 +712,10 @@ dostkoff(void)
p->from.type = D_INDIR+D_SP;
p->from.offset = -(autoffset-75);
p->to.type = D_AX;
if(q1) {
q1->pcond = p;
q1 = P;
}
p = appendp(p);
p->as = ACMPQ;
@ -704,6 +736,10 @@ dostkoff(void)
p->from.type = D_CONST;
p->from.offset = 0;
p->to.type = D_AX;
if(q1) {
q1->pcond = p;
q1 = P;
}
/* 160 comes from 3 calls (3*8) 4 safes (4*8) and 104 guard */
if(autoffset+160 > 4096)