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rewrite RET, indirect CALL, indirect JMP for nacl.

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can JMP or CALL indirect through a register R
provided the preceding instruction is AND $~31, R.

R=ken
OCL=34863
CL=34867
This commit is contained in:
Russ Cox 2009-09-21 15:48:22 -07:00
parent bbcb91a3a7
commit eae0906bed
1 changed files with 66 additions and 3 deletions
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69
src/cmd/8l/span.c
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@ -877,6 +877,22 @@ subreg(Prog *p, int from, int to)
print("%P\n", p);
}
// nacl RET:
// POPL BX
// ANDL BX, $~31
// JMP BX
uchar naclret[] = { 0x5b, 0x83, 0xe3, ~31, 0xff, 0xe3 };
// nacl JMP BX:
// ANDL BX, $~31
// JMP BX
uchar nacljmpbx[] = { 0x83, 0xe3, ~31, 0xff, 0xe3 };
// nacl CALL BX:
// ANDL BX, $~31
// CALL BX
uchar naclcallbx[] = { 0x83, 0xe3, ~31, 0xff, 0xd3 };
void
doasm(Prog *p)
{
@ -936,6 +952,12 @@ found:
break;
case Zlit:
if(HEADTYPE == 8 && p->as == ARET) {
// native client return.
for(z=0; z<sizeof(naclret); z++)
*andptr++ = naclret[z];
break;
}
for(; op = o->op[z]; z++)
*andptr++ = op;
break;
@ -967,6 +989,42 @@ found:
break;
case Zo_m:
if(HEADTYPE == 8) {
Adr a;
switch(p->as) {
case AJMP:
if(p->to.type < D_AX || p->to.type > D_DI)
diag("indirect jmp must use register in native client");
// ANDL $~31, REG
*andptr++ = 0x83;
asmand(&p->to, 04);
*andptr++ = ~31;
// JMP REG
*andptr++ = 0xFF;
asmand(&p->to, 04);
return;
case ACALL:
a = p->to;
// native client indirect call
if(a.type < D_AX || a.type > D_DI) {
// MOVL target into BX
*andptr++ = 0x8b;
asmand(&p->to, reg[D_BX]);
memset(&a, 0, sizeof a);
a.type = D_BX;
}
// ANDL $~31, REG
*andptr++ = 0x83;
asmand(&a, 04);
*andptr++ = ~31;
// CALL REG
*andptr++ = 0xFF;
asmand(&a, 02);
return;
}
}
*andptr++ = op;
asmand(&p->to, o->op[z+1]);
break;
@ -1320,9 +1378,14 @@ asmins(Prog *p)
// - end of call (return address) must be on 32-byte boundary
if(p->as == ATEXT)
p->pc += 31 & -p->pc;
if(p->as == ACALL)
while((p->pc+5)&31)
p->pc++;
if(p->as == ACALL) {
// must end on 32-byte boundary.
// doasm to find out how long the CALL encoding is.
andptr = and;
doasm(p);
npc = p->pc + (andptr - and);
p->pc += 31 & -npc;
}
andptr = and;
doasm(p);
npc = p->pc + (andptr - and);