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32-bit fixes in lessstack.

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avoid tight coupling between deferreturn and jmpdefer.
before, jmpdefer knew the exact frame size of deferreturn
in order to pop it off the stack.  now, deferreturn passes
jmpdefer a pointer to the frame above it explicitly.
that avoids a magic constant and should be less fragile.

R=r
DELTA=32  (6 added, 3 deleted, 23 changed)
OCL=29801
CL=29804
This commit is contained in:
Russ Cox 2009-06-02 23:02:12 -07:00
parent 07393f8706
commit aa3222d88f
4 changed files with 28 additions and 25 deletions
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12
src/runtime/386/asm.s
View File

@ -157,15 +157,17 @@ TEXT cas(SB), 7, $0
MOVL $1, AX
RET
// void jmpdefer(byte*);
// void jmpdefer(fn, sp);
// called from deferreturn.
// 1. pop the caller
// 2. sub 5 bytes from the callers return
// 3. jmp to the argument
TEXT jmpdefer(SB), 7, $0
MOVL 4(SP), AX // function
ADDL $(4+56), SP // pop saved PC and callers frame
SUBL $5, (SP) // reposition his return address
JMP AX // and goto function
MOVL 4(SP), AX // fn
MOVL 8(SP), BX // caller sp
LEAL -4(BX), SP // caller sp after CALL
SUBL $5, (SP) // return to CALL again
JMP AX // but first run the deferred function
TEXT sys·memclr(SB),7,$0
MOVL 4(SP), DI // arg 1 addr

14
src/runtime/amd64/asm.s
View File

@ -172,7 +172,7 @@ TEXT setspgoto(SB), 7, $0
MOVQ AX, SP
PUSHQ CX
JMP BX
POPQ AX
POPQ AX // not reached
RET
// bool cas(int32 *val, int32 old, int32 new)
@ -194,12 +194,14 @@ TEXT cas(SB), 7, $0
MOVL $1, AX
RET
// void jmpdefer(byte*);
// void jmpdefer(fn, sp);
// called from deferreturn.
// 1. pop the caller
// 2. sub 5 bytes from the callers return
// 3. jmp to the argument
TEXT jmpdefer(SB), 7, $0
MOVQ 8(SP), AX // function
ADDQ $(8+56), SP // pop saved PC and callers frame
SUBQ $5, (SP) // reposition his return address
JMP AX // and goto function
MOVQ 8(SP), AX // fn
MOVQ 16(SP), BX // caller sp
LEAQ -8(BX), SP // caller sp after CALL
SUBQ $5, (SP) // return to CALL again
JMP AX // but first run the deferred function

25
src/runtime/proc.c
View File

@ -607,7 +607,7 @@ oldstack(void)
Stktop *top;
uint32 args;
byte *sp;
uint64 oldsp, oldpc, oldbase, oldguard;
uintptr oldsp, oldpc, oldbase, oldguard;
// printf("oldstack m->cret=%p\n", m->cret);
@ -622,10 +622,10 @@ oldstack(void)
mcpy(top->oldsp+2*sizeof(uintptr), sp, args);
}
oldsp = (uint64)top->oldsp + 8;
oldpc = *(uint64*)(top->oldsp + 8);
oldbase = (uint64)top->oldbase;
oldguard = (uint64)top->oldguard;
oldsp = (uintptr)top->oldsp + sizeof(uintptr);
oldpc = *(uintptr*)oldsp;
oldbase = (uintptr)top->oldbase;
oldguard = (uintptr)top->oldguard;
stackfree((byte*)m->curg->stackguard - StackGuard);
@ -645,6 +645,7 @@ oldstack(void)
gogoret(&m->morestack, m->cret);
}
#pragma textflag 7
void
lessstack(void)
{
@ -818,13 +819,11 @@ sys·deferproc(int32 siz, byte* fn, byte* arg0)
#pragma textflag 7
void
sys·deferreturn(int32 arg0)
sys·deferreturn(uintptr arg0)
{
// warning: jmpdefer knows the frame size
// of this routine. dont change anything
// that might change the frame size
Defer *d;
byte *sp;
byte *sp, *fn;
uintptr *caller;
d = g->defer;
if(d == nil)
@ -834,10 +833,10 @@ sys·deferreturn(int32 arg0)
return;
mcpy(d->sp, d->args, d->siz);
g->defer = d->link;
sp = d->fn;
fn = d->fn;
free(d);
jmpdefer(sp);
}
jmpdefer(fn, sp);
}
void
runtime·Breakpoint(void)

2
src/runtime/runtime.h
View File

@ -314,7 +314,7 @@ int32 write(int32, void*, int32);
void close(int32);
int32 fstat(int32, void*);
bool cas(uint32*, uint32, uint32);
void jmpdefer(byte*);
void jmpdefer(byte*, void*);
void exit1(int32);
void ready(G*);
byte* getenv(int8*);