dasm_arm.h

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/*
** DynASM ARM encoding engine.
** Copyright (C) 2005-2023 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       "arm"
 
#ifndef DASM_EXTERN
#define DASM_EXTERN(a,b,c,d)    0
#endif
 
/* Action definitions. */
enum {
  DASM_STOP, DASM_SECTION, DASM_ESC, DASM_REL_EXT,
  /* The following actions need a buffer position. */
  DASM_ALIGN, DASM_REL_LG, DASM_LABEL_LG,
  /* The following actions also have an argument. */
  DASM_REL_PC, DASM_LABEL_PC,
  DASM_IMM, DASM_IMM12, DASM_IMM16, DASM_IMML8, DASM_IMML12, DASM_IMMV8,
  DASM__MAX
};
 
/* 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_REL    0x15000000
#define DASM_S_UNDEF_LG     0x21000000
#define DASM_S_UNDEF_PC     0x22000000
 
/* 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 int *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. */
  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;
  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;
  memset((void *)D->sections, 0, maxsection * sizeof(dasm_Section));
}
 
/* 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;
  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].rbuf = D->sections[i].buf - D->sections[i].pos;
    D->sections[i].ofs = 0;
  }
}
 
 
#ifdef DASM_CHECKS
#define CK(x, st) \
  do { if (!(x)) { \
    D->status = DASM_S_##st|(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|(p-D->actionlist-1); return; } } while (0)
#else
#define CK(x, st)   ((void)0)
#define CKPL(kind, st)  ((void)0)
#endif
 
static int dasm_imm12(unsigned int n)
{
  int i;
  for (i = 0; i < 16; i++, n = (n << 2) | (n >> 30))
    if (n <= 255) return (int)(n + (i << 8));
  return -1;
}
 
/* 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;
  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) {
    unsigned int ins = *p++;
    unsigned int action = (ins >> 16);
    if (action >= DASM__MAX) {
      ofs += 4;
    } else {
      int *pl, n = action >= DASM_REL_PC ? va_arg(ap, int) : 0;
      switch (action) {
      case DASM_STOP: goto stop;
      case DASM_SECTION:
    n = (ins & 255); CK(n < D->maxsection, RANGE_SEC);
    D->section = &D->sections[n]; goto stop;
      case DASM_ESC: p++; ofs += 4; break;
      case DASM_REL_EXT: break;
      case DASM_ALIGN: ofs += (ins & 255); b[pos++] = ofs; break;
      case DASM_REL_LG:
    n = (ins & 2047) - 10; pl = D->lglabels + n;
    /* Bkwd rel or global. */
    if (n >= 0) { CK(n>=10||*pl<0, RANGE_LG); CKPL(lg, LG); goto putrel; }
    pl += 10; n = *pl;
    if (n < 0) n = 0;  /* Start new chain for fwd rel if label exists. */
    goto linkrel;
      case DASM_REL_PC:
    pl = D->pclabels + n; 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++;
    break;
      case DASM_LABEL_LG:
    pl = D->lglabels + (ins & 2047) - 10; CKPL(lg, LG); goto putlabel;
      case DASM_LABEL_PC:
    pl = D->pclabels + n; 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_IMM:
      case DASM_IMM16:
#ifdef DASM_CHECKS
    CK((n & ((1<<((ins>>10)&31))-1)) == 0, RANGE_I);
    if ((ins & 0x8000))
      CK(((n + (1<<(((ins>>5)&31)-1)))>>((ins>>5)&31)) == 0, RANGE_I);
    else
      CK((n>>((ins>>5)&31)) == 0, RANGE_I);
#endif
    b[pos++] = n;
    break;
      case DASM_IMMV8:
    CK((n & 3) == 0, RANGE_I);
    n >>= 2;
    /* fallthrough */
      case DASM_IMML8:
      case DASM_IMML12:
    CK(n >= 0 ? ((n>>((ins>>5)&31)) == 0) :
            (((-n)>>((ins>>5)&31)) == 0), RANGE_I);
    b[pos++] = n;
    break;
      case DASM_IMM12:
    CK(dasm_imm12((unsigned int)n) != -1, RANGE_I);
    b[pos++] = n;
    break;
      }
    }
  }
stop:
  va_end(ap);
  sec->pos = pos;
  sec->ofs = ofs;
}
#undef CK
 
/* Pass 2: Link sections, shrink 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) {
    unsigned int ins = *p++;
    unsigned int action = (ins >> 16);
    switch (action) {
    case DASM_STOP: case DASM_SECTION: goto stop;
    case DASM_ESC: p++; break;
    case DASM_REL_EXT: break;
    case DASM_ALIGN: ofs -= (b[pos++] + ofs) & (ins & 255); break;
    case DASM_REL_LG: case DASM_REL_PC: pos++; break;
    case DASM_LABEL_LG: case DASM_LABEL_PC: b[pos++] += ofs; break;
    case DASM_IMM: case DASM_IMM12: case DASM_IMM16:
    case DASM_IMML8: case DASM_IMML12: case DASM_IMMV8: pos++; break;
    }
      }
      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;
}
 
#ifdef DASM_CHECKS
#define CK(x, st) \
  do { if (!(x)) return DASM_S_##st|(p-D->actionlist-1); } while (0)
#else
#define CK(x, st)   ((void)0)
#endif
 
/* Pass 3: Encode sections. */
int dasm_encode(Dst_DECL, void *buffer)
{
  dasm_State *D = Dst_REF;
  char *base = (char *)buffer;
  unsigned int *cp = (unsigned int *)buffer;
  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++;
      while (1) {
    unsigned int ins = *p++;
    unsigned int action = (ins >> 16);
    int n = (action >= DASM_ALIGN && action < DASM__MAX) ? *b++ : 0;
    switch (action) {
    case DASM_STOP: case DASM_SECTION: goto stop;
    case DASM_ESC: *cp++ = *p++; break;
    case DASM_REL_EXT:
      n = DASM_EXTERN(Dst, (unsigned char *)cp, (ins&2047), !(ins&2048));
      goto patchrel;
    case DASM_ALIGN:
      ins &= 255; while ((((char *)cp - base) & ins)) *cp++ = 0xe1a00000;
      break;
    case DASM_REL_LG:
      if (n < 0) {
        n = (int)((ptrdiff_t)D->globals[-n-10] - (ptrdiff_t)cp - 4);
        goto patchrel;
      }
      /* fallthrough */
    case DASM_REL_PC:
      CK(n >= 0, UNDEF_PC);
      n = *DASM_POS2PTR(D, n) - (int)((char *)cp - base) - 4;
    patchrel:
      if ((ins & 0x800) == 0) {
        CK((n & 3) == 0 && ((n+0x02000000) >> 26) == 0, RANGE_REL);
        cp[-1] |= ((n >> 2) & 0x00ffffff);
      } else if ((ins & 0x1000)) {
        CK((n & 3) == 0 && -256 <= n && n <= 256, RANGE_REL);
        goto patchimml8;
      } else if ((ins & 0x2000) == 0) {
        CK((n & 3) == 0 && -4096 <= n && n <= 4096, RANGE_REL);
        goto patchimml;
      } else {
        CK((n & 3) == 0 && -1020 <= n && n <= 1020, RANGE_REL);
        n >>= 2;
        goto patchimml;
      }
      break;
    case DASM_LABEL_LG:
      ins &= 2047; if (ins >= 20) D->globals[ins-20] = (void *)(base + n);
      break;
    case DASM_LABEL_PC: break;
    case DASM_IMM:
      cp[-1] |= ((n>>((ins>>10)&31)) & ((1<<((ins>>5)&31))-1)) << (ins&31);
      break;
    case DASM_IMM12:
      cp[-1] |= dasm_imm12((unsigned int)n);
      break;
    case DASM_IMM16:
      cp[-1] |= ((n & 0xf000) << 4) | (n & 0x0fff);
      break;
    case DASM_IMML8: patchimml8:
      cp[-1] |= n >= 0 ? (0x00800000 | (n & 0x0f) | ((n & 0xf0) << 4)) :
                 ((-n & 0x0f) | ((-n & 0xf0) << 4));
      break;
    case DASM_IMML12: case DASM_IMMV8: patchimml:
      cp[-1] |= n >= 0 ? (0x00800000 | n) : (-n);
      break;
    default: *cp++ = ins; break;
    }
      }
      stop: (void)0;
    }
  }
 
  if (base + D->codesize != (char *)cp)  /* Check for phase errors. */
    return DASM_S_PHASE;
  return DASM_S_OK;
}
#undef CK
 
/* 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_LG|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|(D->section-D->sections);
  return D->status;
}
#endif