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Disassembler: select table based on VEX prefixes

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We can use the new VEX prefixes to select into a large table of new
opcode spaces.  Since the table is (currently) sparse, add logic so we
don't end up producing tons of empty tables for no good reason.

This is also necessary since VEX is likely to reuse opcode bytes that
would appear as prefixes at some point, which would cause conflicts
with the regular tables.
This commit is contained in:
H. Peter Anvin 2008-05-21 11:05:39 -07:00
parent eb9e093840
commit 2fb033af18
3 changed files with 57 additions and 5 deletions
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15
disasm.c
View File

@ -1021,6 +1021,8 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
segover = NULL;
origdata = data;
ix = itable;
end_prefix = false;
while (!end_prefix) {
switch (*data) {
@ -1028,9 +1030,11 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
case 0xF3:
prefix.rep = *data++;
break;
case 0xF0:
prefix.lock = *data++;
break;
case 0x2E:
segover = "cs", prefix.seg = *data++;
break;
@ -1049,6 +1053,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
case 0x65:
segover = "gs", prefix.seg = *data++;
break;
case 0x66:
prefix.osize = (segsize == 16) ? 32 : 16;
prefix.osp = *data++;
@ -1057,6 +1062,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
prefix.asize = (segsize == 32) ? 16 : 32;
prefix.asp = *data++;
break;
case 0xC4:
case 0xC5:
if (segsize == 64 || (data[1] & 0xc0) == 0xc0) {
@ -1078,8 +1084,11 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
prefix.vex_v = (~prefix.vex[1] >> 3) & 15;
prefix.vex_lp = prefix.vex[1] & 7;
}
ix = itable_VEX[prefix.vex_m][prefix.vex_lp];
end_prefix = true;
break;
case REX_P + 0x0:
case REX_P + 0x1:
case REX_P + 0x2:
@ -1103,6 +1112,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
}
end_prefix = true;
break;
default:
end_prefix = true;
break;
@ -1113,8 +1123,11 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
best_p = NULL;
best_pref = INT_MAX;
if (!ix)
return 0; /* No instruction table at all... */
dp = data;
ix = itable + *dp++;
ix += *dp++;
while (ix->n == -1) {
ix = (const struct disasm_index *)ix->p + *dp++;
}

1
insns.h
View File

@ -32,6 +32,7 @@ struct disasm_index {
/* Tables for the assembler and disassembler, respectively */
extern const struct itemplate * const nasm_instructions[];
extern const struct disasm_index itable[256];
extern const struct disasm_index * const itable_VEX[32][8];
/* Common table for the byte codes */
extern const uint8_t nasm_bytecodes[];

46
insns.pl
View File

@ -14,6 +14,15 @@
# This should match MAX_OPERANDS from nasm.h
$MAX_OPERANDS = 5;
# Add VEX prefixes
@vexlist = ();
for ($m = 0; $m < 32; $m++) {
for ($lp = 0; $lp < 8; $lp++) {
push(@vexlist, sprintf("VEX%02X%01X", $m, $lp));
}
}
@disasm_prefixes = (@vexlist, @disasm_prefixes);
print STDERR "Reading insns.dat...\n";
@args = ();
@ -182,8 +191,20 @@ if ( !defined($output) || $output eq 'd' ) {
print D "};\n";
}
@prefix_list = ();
foreach $h (@disasm_prefixes, '') {
$is_prefix{$h} = 1;
for ($c = 0; $c < 256; $c++) {
$nn = sprintf("%s%02X", $h, $c);
if ($is_prefix{$nn} || defined($dinstables{$nn})) {
# At least one entry in this prefix table
push(@prefix_list, $h);
$is_prefix{$h} = 1;
last;
}
}
}
foreach $h (@prefix_list) {
print D "\n";
print D "static " unless ($h eq '');
print D "const struct disasm_index ";
@ -202,9 +223,24 @@ if ( !defined($output) || $output eq 'd' ) {
printf D " { NULL, 0 },\n";
}
}
print D "};\n";
print D "};\n";
}
print D "\nconst struct disasm_index * const itable_VEX[32][8] = {\n";
for ($m = 0; $m < 32; $m++) {
print D "\t{\n";
for ($lp = 0; $lp < 8; $lp++) {
$vp = sprintf("VEX%02X%01X", $m, $lp);
if ($is_prefix{$vp}) {
printf D "\t\titable_%s,\n", $vp;
} else {
print D "\t\tNULL,\n";
}
}
print D "\t},\n";
}
print D "};\n";
close D;
}
@ -464,8 +500,10 @@ sub startseq($) {
} elsif ($c0 == 0 || $c0 == 0340) {
return $prefix;
} elsif (($c0 & ~3) == 0260 || $c0 == 0270) {
shift(@codes); # Skip VEX control bytes
shift(@codes);
my $m,$wlp,$vxp;
$m = shift(@codes);
$wlp = shift(@codes);
$prefix .= sprintf('VEX%02X%01X', $m, $wlp & 7);
} elsif ($c0 >= 0172 && $c0 <= 174) {
shift(@codes); # Skip is4 control byte
} else {