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/*
** DynASM x86 encoding engine.
** Copyright (C) 2005-2015 Mike Pall. All rights reserved.
** Released under the MIT license. See dynasm.lua for full copyright notice.
*/
#include <stddef.h>
#include <stdarg.h>
#include <string.h>
#include <stdlib.h>
#define DASM_ARCH "x86"
#ifndef DASM_EXTERN
#define DASM_EXTERN(a,b,c,d) 0
#endif
/* Action definitions. DASM_STOP must be 255. */
enum
{
DASM_DISP = 231,
DASM_IMM_S, DASM_IMM_B, DASM_IMM_W, DASM_IMM_D, DASM_IMM_WB, DASM_IMM_DB,
DASM_VREG, DASM_SPACE, DASM_SETLABEL, DASM_REL_A, DASM_REL_LG, DASM_REL_PC,
DASM_IMM_LG, DASM_IMM_PC, DASM_LABEL_LG, DASM_LABEL_PC, DASM_ALIGN,
DASM_EXTERN, DASM_ESC, DASM_MARK, DASM_MARKREX, DASM_OPTREX,
DASM_SECTION, DASM_STOP
};
/* Maximum number of section buffer positions for a single dasm_put() call. */
#define DASM_MAXSECPOS 25
/* DynASM encoder status codes. Action list offset or number are or'ed in. */
#define DASM_S_OK 0x00000000
#define DASM_S_NOMEM 0x01000000
#define DASM_S_PHASE 0x02000000
#define DASM_S_MATCH_SEC 0x03000000
#define DASM_S_RANGE_I 0x11000000
#define DASM_S_RANGE_SEC 0x12000000
#define DASM_S_RANGE_LG 0x13000000
#define DASM_S_RANGE_PC 0x14000000
#define DASM_S_RANGE_VREG 0x15000000
#define DASM_S_UNDEF_L 0x21000000
#define DASM_S_UNDEF_PC 0x22000000
#define DASM_S_RSP_SIB_IDX 0x23000000
/* Macros to convert positions (8 bit section + 24 bit index). */
#define DASM_POS2IDX(pos) ((pos)&0x00ffffff)
#define DASM_POS2BIAS(pos) ((pos)&0xff000000)
#define DASM_SEC2POS(sec) ((sec)<<24)
#define DASM_POS2SEC(pos) ((pos)>>24)
#define DASM_POS2PTR(D, pos) (D->sections[DASM_POS2SEC(pos)].rbuf + (pos))
/* Action list type. */
typedef const unsigned char *dasm_ActList;
/* Per-section structure. */
typedef struct dasm_Section
{
int *rbuf; /* Biased buffer pointer (negative section bias). */
int *buf; /* True buffer pointer. */
size_t bsize; /* Buffer size in bytes. */
int pos; /* Biased buffer position. */
int epos; /* End of biased buffer position - max single put. */
int ofs; /* Byte offset into section. */
} dasm_Section;
/* Core structure holding the DynASM encoding state. */
struct dasm_State
{
size_t psize; /* Allocated size of this structure. */
dasm_ActList actionlist; /* Current actionlist pointer. */
int *lglabels; /* Local/global chain/pos ptrs. */
size_t lgsize;
int *pclabels; /* PC label chains/pos ptrs. */
size_t pcsize;
void **globals; /* Array of globals (bias -10). */
dasm_Section *section; /* Pointer to active section. */
size_t codesize; /* Total size of all code sections. */
int maxsection; /* 0 <= sectionidx < maxsection. */
int status; /* Status code. */
dasm_Section sections[1]; /* All sections. Alloc-extended. */
};
/* The size of the core structure depends on the max. number of sections. */
#define DASM_PSZ(ms) (sizeof(dasm_State)+(ms-1)*sizeof(dasm_Section))
/* Initialize DynASM state. */
void
dasm_init (Dst_DECL, int maxsection)
{
dasm_State *D;
size_t psz = 0;
int i;
Dst_REF = NULL;
DASM_M_GROW (Dst, struct dasm_State, Dst_REF, psz, DASM_PSZ (maxsection));
D = Dst_REF;
D->psize = psz;
D->lglabels = NULL;
D->lgsize = 0;
D->pclabels = NULL;
D->pcsize = 0;
D->globals = NULL;
D->maxsection = maxsection;
for (i = 0; i < maxsection; i++)
{
D->sections[i].buf = NULL; /* Need this for pass3. */
D->sections[i].rbuf = D->sections[i].buf - DASM_SEC2POS (i);
D->sections[i].bsize = 0;
D->sections[i].epos = 0; /* Wrong, but is recalculated after resize. */
}
}
/* Free DynASM state. */
void
dasm_free (Dst_DECL)
{
dasm_State *D = Dst_REF;
int i;
for (i = 0; i < D->maxsection; i++)
if (D->sections[i].buf)
DASM_M_FREE (Dst, D->sections[i].buf, D->sections[i].bsize);
if (D->pclabels)
DASM_M_FREE (Dst, D->pclabels, D->pcsize);
if (D->lglabels)
DASM_M_FREE (Dst, D->lglabels, D->lgsize);
DASM_M_FREE (Dst, D, D->psize);
}
/* Setup global label array. Must be called before dasm_setup(). */
void
dasm_setupglobal (Dst_DECL, void **gl, unsigned int maxgl)
{
dasm_State *D = Dst_REF;
D->globals = gl - 10; /* Negative bias to compensate for locals. */
DASM_M_GROW (Dst, int, D->lglabels, D->lgsize, (10 + maxgl) * sizeof (int));
}
/* Grow PC label array. Can be called after dasm_setup(), too. */
void
dasm_growpc (Dst_DECL, unsigned int maxpc)
{
dasm_State *D = Dst_REF;
size_t osz = D->pcsize;
DASM_M_GROW (Dst, int, D->pclabels, D->pcsize, maxpc * sizeof (int));
memset ((void *) (((unsigned char *) D->pclabels) + osz), 0,
D->pcsize - osz);
}
/* Setup encoder. */
void
dasm_setup (Dst_DECL, const void *actionlist)
{
dasm_State *D = Dst_REF;
int i;
D->actionlist = (dasm_ActList) actionlist;
D->status = DASM_S_OK;
D->section = &D->sections[0];
memset ((void *) D->lglabels, 0, D->lgsize);
if (D->pclabels)
memset ((void *) D->pclabels, 0, D->pcsize);
for (i = 0; i < D->maxsection; i++)
{
D->sections[i].pos = DASM_SEC2POS (i);
D->sections[i].ofs = 0;
}
}
#ifdef DASM_CHECKS
#define CK(x, st) \
do { if (!(x)) { \
D->status = DASM_S_##st|(int)(p-D->actionlist-1); return; } } while (0)
#define CKPL(kind, st) \
do { if ((size_t)((char *)pl-(char *)D->kind##labels) >= D->kind##size) { \
D->status=DASM_S_RANGE_##st|(int)(p-D->actionlist-1); return; } } while (0)
#else
#define CK(x, st) ((void)0)
#define CKPL(kind, st) ((void)0)
#endif
/* Pass 1: Store actions and args, link branches/labels, estimate offsets. */
void
dasm_put (Dst_DECL, int start, ...)
{
va_list ap;
dasm_State *D = Dst_REF;
dasm_ActList p = D->actionlist + start;
dasm_Section *sec = D->section;
int pos = sec->pos, ofs = sec->ofs, mrm = 4, optrex = -1;
int *b;
if (pos >= sec->epos)
{
DASM_M_GROW (Dst, int, sec->buf, sec->bsize,
sec->bsize + 2 * DASM_MAXSECPOS * sizeof (int));
sec->rbuf = sec->buf - DASM_POS2BIAS (pos);
sec->epos =
(int) sec->bsize / sizeof (int) - DASM_MAXSECPOS +
DASM_POS2BIAS (pos);
}
b = sec->rbuf;
b[pos++] = start;
va_start (ap, start);
while (1)
{
int action = *p++;
if (action < DASM_DISP)
{
ofs++;
}
else if (action <= DASM_REL_A)
{
int n = va_arg (ap, int);
b[pos++] = n;
switch (action)
{
case DASM_DISP:
if (n == 0)
break;
case DASM_IMM_DB:
if (((n + 128) & -256) == 0)
goto ob;
case DASM_REL_A: /* Assumes ptrdiff_t is int. !x64 */
case DASM_IMM_D:
ofs += 4;
break;
case DASM_IMM_S:
CK (((n + 128) & -256) == 0, RANGE_I);
goto ob;
case DASM_IMM_B:
CK ((n & -256) == 0, RANGE_I);
ob:ofs++;
break;
case DASM_IMM_WB:
if (((n + 128) & -256) == 0)
goto ob;
case DASM_IMM_W:
CK ((n & -65536) == 0, RANGE_I);
ofs += 2;
break;
case DASM_SPACE:
p++;
ofs += n;
break;
case DASM_SETLABEL:
b[pos - 2] = -0x40000000;
break; /* Neg. label ofs. */
case DASM_VREG:
CK ((n & -16) == 0 && (n != 4 || (*p & 1) == 0), RANGE_VREG);
if ((*p++ & 3) == 1 && *p == DASM_DISP)
mrm = n;
if (optrex > 0)
b[optrex] |= n;
/* we might need an extra byte for RSP/RBP special encoding */
ofs++;
continue;
}
mrm = 4;
}
else
{
int *pl, n;
switch (action)
{
case DASM_REL_LG:
case DASM_IMM_LG:
n = *p++;
pl = D->lglabels + n;
/* Bkwd rel or global. */
if (n <= 246)
{
CK (n >= 10 || *pl < 0, RANGE_LG);
CKPL (lg, LG);
goto putrel;
}
pl -= 246;
n = *pl;
if (n < 0)
n = 0; /* Start new chain for fwd rel if label exists. */
goto linkrel;
case DASM_REL_PC:
case DASM_IMM_PC:
pl = D->pclabels + va_arg (ap, int);
CKPL (pc, PC);
putrel:
n = *pl;
if (n < 0)
{ /* Label exists. Get label pos and store it. */
b[pos] = -n;
}
else
{
linkrel:
b[pos] = n; /* Else link to rel chain, anchored at label. */
*pl = pos;
}
pos++;
ofs += 4; /* Maximum offset needed. */
if (action == DASM_REL_LG || action == DASM_REL_PC)
b[pos++] = ofs; /* Store pass1 offset estimate. */
break;
case DASM_LABEL_LG:
pl = D->lglabels + *p++;
CKPL (lg, LG);
goto putlabel;
case DASM_LABEL_PC:
pl = D->pclabels + va_arg (ap, int);
CKPL (pc, PC);
putlabel:
n = *pl; /* n > 0: Collapse rel chain and replace with label pos. */
while (n > 0)
{
int *pb = DASM_POS2PTR (D, n);
n = *pb;
*pb = pos;
}
*pl = -pos; /* Label exists now. */
b[pos++] = ofs; /* Store pass1 offset estimate. */
break;
case DASM_ALIGN:
ofs += *p++; /* Maximum alignment needed (arg is 2**n-1). */
b[pos++] = ofs; /* Store pass1 offset estimate. */
break;
case DASM_EXTERN:
p += 2;
ofs += 4;
break;
case DASM_ESC:
p++;
ofs++;
break;
case DASM_MARK:
mrm = p[-2];
break;
case DASM_MARKREX:
optrex = -1;
break;
case DASM_OPTREX:
/* Add space for arguments */
optrex = pos;
b[pos++] = 0;
ofs++;
break;
case DASM_SECTION:
n = *p;
CK (n < D->maxsection, RANGE_SEC);
D->section = &D->sections[n];
case DASM_STOP:
goto stop;
}
}
}
stop:
va_end (ap);
sec->pos = pos;
sec->ofs = ofs;
}
#undef CK
/* Pass 2: Link sections, shrink branches/aligns, fix label offsets. */
int
dasm_link (Dst_DECL, size_t * szp)
{
dasm_State *D = Dst_REF;
int secnum;
int ofs = 0;
#ifdef DASM_CHECKS
*szp = 0;
if (D->status != DASM_S_OK)
return D->status;
{
int pc;
for (pc = 0; pc * sizeof (int) < D->pcsize; pc++)
if (D->pclabels[pc] > 0)
return DASM_S_UNDEF_PC | pc;
}
#endif
{ /* Handle globals not defined in this translation unit. */
int idx;
for (idx = 10; idx * sizeof (int) < D->lgsize; idx++)
{
int n = D->lglabels[idx];
/* Undefined label: Collapse rel chain and replace with marker (< 0). */
while (n > 0)
{
int *pb = DASM_POS2PTR (D, n);
n = *pb;
*pb = -idx;
}
}
}
/* Combine all code sections. No support for data sections (yet). */
for (secnum = 0; secnum < D->maxsection; secnum++)
{
dasm_Section *sec = D->sections + secnum;
int *b = sec->rbuf;
int pos = DASM_SEC2POS (secnum);
int lastpos = sec->pos;
while (pos != lastpos)
{
dasm_ActList p = D->actionlist + b[pos++];
while (1)
{
int op, action = *p++;
switch (action)
{
case DASM_REL_LG:
p++;
op = p[-3];
goto rel_pc;
case DASM_REL_PC:
op = p[-2];
rel_pc:{
int shrink =
op == 0xe9 ? 3 : ((op & 0xf0) == 0x80 ? 4 : 0);
if (shrink)
{ /* Shrinkable branch opcode? */
int lofs, lpos = b[pos];
if (lpos < 0)
goto noshrink; /* Ext global? */
lofs = *DASM_POS2PTR (D, lpos);
if (lpos > pos)
{ /* Fwd label: add cumulative section offsets. */
int i;
for (i = secnum; i < DASM_POS2SEC (lpos); i++)
lofs += D->sections[i].ofs;
}
else
{
lofs -= ofs; /* Bkwd label: unfix offset. */
}
lofs -= b[pos + 1]; /* Short branch ok? */
if (lofs >= -128 - shrink && lofs <= 127)
ofs -= shrink; /* Yes. */
else
{
noshrink:shrink = 0;
} /* No, cannot shrink op. */
}
b[pos + 1] = shrink;
pos += 2;
break;
}
case DASM_VREG:
{
int val = b[pos++];
int flag = *p++;
int type = (flag & 3);
int mode = ((flag >> 2) & 3);
int shrink = 1;
/* fprintf(stderr, "VREG: mode = %d, type = %d, val=%d\n", mode, type, val); */
if (mode != 3 && type == 0 && (val&7) == 4) {
shrink = 0;
} else if ((val&7) == 5 && (type < 2) && *p == DASM_DISP && b[pos] == 0) {
/* extra byte is necessary for rbp encoding, which is weird again */
shrink = 0;
}
/* adjust ofs if we don't need the extra byte */
ofs -= shrink;
break;
}
case DASM_SPACE:
case DASM_IMM_LG:
p++;
case DASM_DISP:
case DASM_IMM_S:
case DASM_IMM_B:
case DASM_IMM_W:
case DASM_IMM_D:
case DASM_IMM_WB:
case DASM_IMM_DB:
case DASM_SETLABEL:
case DASM_REL_A:
case DASM_IMM_PC:
pos++;
break;
case DASM_LABEL_LG:
p++;
case DASM_LABEL_PC:
b[pos++] += ofs;
break; /* Fix label offset. */
case DASM_ALIGN:
ofs -= (b[pos++] + ofs) & *p++;
break; /* Adjust ofs. */
case DASM_EXTERN:
p += 2;
break;
case DASM_ESC:
p++;
break;
case DASM_MARK:
break;
case DASM_MARKREX:
break;
case DASM_OPTREX:
if (~b[pos] & 8) {
ofs--; /* ofs should only decrease */
}
pos++;
break;
case DASM_SECTION:
case DASM_STOP:
goto stop;
}
}
stop:(void) 0;
}
ofs += sec->ofs; /* Next section starts right after current section. */
}
D->codesize = ofs; /* Total size of all code sections */
*szp = ofs;
return DASM_S_OK;
}
#define dasmb(x) *cp++ = (unsigned char)(x)
#ifndef DASM_ALIGNED_WRITES
#define dasmw(x) \
do { *((unsigned short *)cp) = (unsigned short)(x); cp+=2; } while (0)
#define dasmd(x) \
do { *((unsigned int *)cp) = (unsigned int)(x); cp+=4; } while (0)
#else
#define dasmw(x) do { dasmb(x); dasmb((x)>>8); } while (0)
#define dasmd(x) do { dasmw(x); dasmw((x)>>16); } while (0)
#endif
/* Pass 3: Encode sections. */
int
dasm_encode (Dst_DECL, void *buffer)
{
dasm_State *D = Dst_REF;
unsigned char *base = (unsigned char *) buffer;
unsigned char *cp = base;
int secnum;
/* Encode all code sections. No support for data sections (yet). */
for (secnum = 0; secnum < D->maxsection; secnum++)
{
dasm_Section *sec = D->sections + secnum;
int *b = sec->buf;
int *endb = sec->rbuf + sec->pos;
while (b != endb)
{
dasm_ActList p = D->actionlist + *b++;
unsigned char *mark = NULL, *rex = NULL;
while (1)
{
int action = *p++;
int n = (action >= DASM_DISP
&& action <= DASM_ALIGN) ? *b++ : 0;
switch (action)
{
case DASM_DISP:
if (!mark)
mark = cp;
{
unsigned char *mm = mark;
if (*p != DASM_IMM_DB && *p != DASM_IMM_WB)
mark = NULL;
if (n == 0)
{
int mrm = mm[-1] & 7;
if (mrm == 4)
mrm = mm[0] & 7;
if (mrm != 5)
{
mm[-1] -= 0x80;
break;
}
}
if (((n + 128) & -256) != 0)
goto wd;
else
mm[-1] -= 0x40;
}
case DASM_IMM_S:
case DASM_IMM_B:
wb:dasmb (n);
break;
case DASM_IMM_DB:
if (((n + 128) & -256) == 0)
{
db:if (!mark)
mark = cp;
mark[-2] += 2;
mark = NULL;
goto wb;
}
else
mark = NULL;
case DASM_IMM_D:
wd:dasmd (n);
break;
case DASM_IMM_WB:
if (((n + 128) & -256) == 0)
goto db;
else
mark = NULL;
case DASM_IMM_W:
dasmw (n);
break;
case DASM_VREG:
{
int flag = *p++;
int type = flag & 3; /* 0 = ModRM.RM, 1 = SIB.base, 2 = ModRM.reg, 3 = SIB.idx */
int mode = (flag >> 2) & 3;
int addr = (n & 7); /* only the three LSB go into the address */
/* fprintf(stderr, "mode: %d addr %d type %d\n", mode, n, type); */
if (addr == 4 && mode != 3 && type == 0) {
/* RSP/R12 byte encoding is irregular */
cp[-1] |= 4;
*cp++ = 0x24;
} else if (n == 4 && type == 3) {
/* fprintf(stderr, "FAIL! cannot encode rsp as SIB.idx\n"); */
return DASM_S_RSP_SIB_IDX;
} else {
/* Normal happy case */
if (type >= 2)
addr <<= 3;
cp[-1] |= addr; /* add in the address bits */
}
if (rex && (n & 8)==8) {
*rex |= ((type < 2) ? 1 : /* rex.b */
(type == 2) ? 4 /* rex.r */ : 2 /* rex.x */);
}
/* we reuse the same REX byte for multiple operands */
break;
}
case DASM_REL_LG:
p++;
if (n >= 0)
goto rel_pc;
b++;
n = (int) (ptrdiff_t) D->globals[-n];
case DASM_REL_A:
rel_a:n -= (int) (ptrdiff_t) (cp + 4);
goto wd; /* !x64 */
case DASM_REL_PC:
rel_pc:{
int shrink = *b++;
int *pb = DASM_POS2PTR (D, n);
if (*pb < 0)
{
n = pb[1];
goto rel_a;
}
n = *pb - ((int) (cp - base) + 4 - shrink);
if (shrink == 0)
goto wd;
if (shrink == 4)
{
cp--;
cp[-1] = *cp - 0x10;
}
else
cp[-1] = 0xeb;
goto wb;
}
case DASM_IMM_LG:
p++;
if (n < 0)
{
n = (int) (ptrdiff_t) D->globals[-n];
goto wd;
}
case DASM_IMM_PC:
{
int *pb = DASM_POS2PTR (D, n);
n = *pb < 0 ? pb[1] : (*pb + (int) (ptrdiff_t) base);
goto wd;
}
case DASM_LABEL_LG:
{
int idx = *p++;
if (idx >= 10)
D->globals[idx] =
(void *) (base + (*p == DASM_SETLABEL ? *b : n));
break;
}
case DASM_LABEL_PC:
case DASM_SETLABEL:
break;
case DASM_SPACE:
{
int fill = *p++;
while (n--)
*cp++ = fill;
break;
}
case DASM_ALIGN:
n = *p++;
while (((cp - base) & n))
*cp++ = 0x90; /* nop */
break;
case DASM_EXTERN:
n = DASM_EXTERN (Dst, cp, p[1], *p);
p += 2;
goto wd;
case DASM_MARK:
mark = cp;
break;
case DASM_MARKREX:
rex = cp-1;
break;
case DASM_OPTREX:
if (*b++ & 8) {
rex = cp;
*cp++ = 64;
}
break;
case DASM_ESC:
action = *p++;
default:
*cp++ = action;
break;
case DASM_SECTION:
case DASM_STOP:
goto stop;
}
}
stop:(void) 0;
}
}
if (base + D->codesize != cp) { /* Check for phase errors. */
/* fprintf(stderr, "Overshoot of %d bytes\n", cp - (base + D->codesize)); */
return DASM_S_PHASE;
}
return DASM_S_OK;
}
/* Get PC label offset. */
int
dasm_getpclabel (Dst_DECL, unsigned int pc)
{
dasm_State *D = Dst_REF;
if (pc * sizeof (int) < D->pcsize)
{
int pos = D->pclabels[pc];
if (pos < 0)
return *DASM_POS2PTR (D, -pos);
if (pos > 0)
return -1; /* Undefined. */
}
return -2; /* Unused or out of range. */
}
#ifdef DASM_CHECKS
/* Optional sanity checker to call between isolated encoding steps. */
int
dasm_checkstep (Dst_DECL, int secmatch)
{
dasm_State *D = Dst_REF;
if (D->status == DASM_S_OK)
{
int i;
for (i = 1; i <= 9; i++)
{
if (D->lglabels[i] > 0)
{
D->status = DASM_S_UNDEF_L | i;
break;
}
D->lglabels[i] = 0;
}
}
if (D->status == DASM_S_OK && secmatch >= 0 &&
D->section != &D->sections[secmatch])
D->status = DASM_S_MATCH_SEC | (int) (D->section - D->sections);
return D->status;
}
#endif
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