src/buildvm_asm.c

   1 /*
   2 ** LuaJIT VM builder: Assembler source code emitter.
   3 ** Copyright (C) 2005-2010 Mike Pall. See Copyright Notice in luajit.h
   4 */
   5
   6 #include "buildvm.h"
   7 #include "lj_bc.h"
   8
   9 /* ------------------------------------------------------------------------ */
  10
  11 /* Emit bytes piecewise as assembler text. */
  12 static void emit_asm_bytes(BuildCtx *ctx, uint8_t *p, int n)
  13 {
  14   int i;
  15   for (i = 0; i < n; i++) {
  16     if ((i & 15) == 0)
  17       fprintf(ctx->fp, "\t.byte %d", p[i]);
  18     else
  19       fprintf(ctx->fp, ",%d", p[i]);
  20     if ((i & 15) == 15) putc('\n', ctx->fp);
  21   }
  22   if ((n & 15) != 0) putc('\n', ctx->fp);
  23 }
  24
  25 /* Emit relocation */
  26 static void emit_asm_reloc(BuildCtx *ctx, BuildReloc *r)
  27 {
  28   const char *sym = ctx->extnames[r->sym];
  29   const char *p = strchr(sym, '@');
  30   char buf[80];
  31   if (p) {
  32     /* Always strip fastcall suffix. Wrong for (unused) COFF on Win32. */
  33     strncpy(buf, sym, p-sym);
  34     buf[p-sym] = '\0';
  35     sym = buf;
  36   }
  37   switch (ctx->mode) {
  38   case BUILD_elfasm:
  39     if (r->type)
  40       fprintf(ctx->fp, "\t.long %s-.-4\n", sym);
  41     else
  42       fprintf(ctx->fp, "\t.long %s\n", sym);
  43     break;
  44   case BUILD_coffasm:
  45     fprintf(ctx->fp, "\t.def _%s; .scl 3; .type 32; .endef\n", sym);
  46     if (r->type)
  47       fprintf(ctx->fp, "\t.long _%s-.-4\n", sym);
  48     else
  49       fprintf(ctx->fp, "\t.long _%s\n", sym);
  50     break;
  51   default:  /* BUILD_machasm for relative relocations handled below. */
  52     fprintf(ctx->fp, "\t.long _%s\n", sym);
  53     break;
  54   }
  55 }
  56
  57 static const char *const jccnames[] = {
  58   "jo", "jno", "jb", "jnb", "jz", "jnz", "jbe", "ja",
  59   "js", "jns", "jpe", "jpo", "jl", "jge", "jle", "jg"
  60 };
  61
  62 /* Emit relocation for the incredibly stupid OSX assembler. */
  63 static void emit_asm_reloc_mach(BuildCtx *ctx, uint8_t *cp, int n,
  64                                 const char *sym)
  65 {
  66   const char *opname = NULL;
  67   if (--n < 0) goto err;
  68   if (cp[n] == 0xe8) {
  69     opname = "call";
  70   } else if (cp[n] == 0xe9) {
  71     opname = "jmp";
  72   } else if (cp[n] >= 0x80 && cp[n] <= 0x8f && n > 0 && cp[n-1] == 0x0f) {
  73     opname = jccnames[cp[n]-0x80];
  74     n--;
  75   } else {
  76 err:
  77     fprintf(stderr, "Error: unsupported opcode for %s symbol relocation.\n",
  78             sym);
  79     exit(1);
  80   }
  81   emit_asm_bytes(ctx, cp, n);
  82   fprintf(ctx->fp, "\t%s _%s\n", opname, sym);
  83 }
  84
  85 /* Emit an assembler label. */
  86 static void emit_asm_label(BuildCtx *ctx, const char *name, int size, int isfunc)
  87 {
  88   switch (ctx->mode) {
  89   case BUILD_elfasm:
  90     fprintf(ctx->fp,
  91       "\n\t.globl %s\n"
  92       "\t.hidden %s\n"
  93       "\t.type %s, @%s\n"
  94       "\t.size %s, %d\n"
  95       "%s:\n",
  96       name, name, name, isfunc ? "function" : "object", name, size, name);
  97     break;
  98   case BUILD_coffasm:
  99     fprintf(ctx->fp, "\n\t.globl _%s\n", name);
 100     if (isfunc)
 101       fprintf(ctx->fp, "\t.def _%s; .scl 3; .type 32; .endef\n", name);
 102     fprintf(ctx->fp, "_%s:\n", name);
 103     break;
 104   case BUILD_machasm:
 105     fprintf(ctx->fp,
 106       "\n\t.private_extern _%s\n"
 107       "_%s:\n", name, name);
 108     break;
 109   default:
 110     break;
 111   }
 112 }
 113
 114 /* Emit alignment. */
 115 static void emit_asm_align(BuildCtx *ctx, int bits)
 116 {
 117   switch (ctx->mode) {
 118   case BUILD_elfasm:
 119   case BUILD_coffasm:
 120     fprintf(ctx->fp, "\t.p2align %d\n", bits);
 121     break;
 122   case BUILD_machasm:
 123     fprintf(ctx->fp, "\t.align %d\n", bits);
 124     break;
 125   default:
 126     break;
 127   }
 128 }
 129
 130 /* ------------------------------------------------------------------------ */
 131
 132 /* Emit assembler source code. */
 133 void emit_asm(BuildCtx *ctx)
 134 {
 135   char name[80];
 136   int32_t prev;
 137   int i, pi, rel;
 138
 139   fprintf(ctx->fp, "\t.file \"buildvm_%s.dasc\"\n", ctx->dasm_arch);
 140   fprintf(ctx->fp, "\t.text\n");
 141   emit_asm_align(ctx, 4);
 142
 143   emit_asm_label(ctx, LABEL_ASM_BEGIN, 0, 0);
 144   if (ctx->mode == BUILD_elfasm)
 145     fprintf(ctx->fp, ".Lbegin:\n");
 146
 147   i = 0;
 148   do {
 149     pi = ctx->perm[i++];
 150     prev = ctx->sym_ofs[pi];
 151   } while (prev < 0);  /* Skip the _Z symbols. */
 152
 153   for (rel = 0; i <= ctx->nsym; i++) {
 154     int ni = ctx->perm[i];
 155     int32_t next = ctx->sym_ofs[ni];
 156     int size = (int)(next - prev);
 157     int32_t stop = next;
 158     if (pi >= ctx->npc) {
 159       char *p;
 160       sprintf(name, LABEL_PREFIX "%s", ctx->globnames[pi-ctx->npc]);
 161       /* Always strip fastcall suffix. Wrong for (unused) COFF on Win32. */
 162       p = strchr(name, '@');
 163       if (p) *p = '\0';
 164       emit_asm_label(ctx, name, size, 1);
 165 #if LJ_HASJIT
 166     } else {
 167 #else
 168     } else if (!(pi == BC_JFORI || pi == BC_JFORL || pi == BC_JITERL ||
 169                  pi == BC_JLOOP || pi == BC_IFORL || pi == BC_IITERL ||
 170                  pi == BC_ILOOP)) {
 171 #endif
 172       sprintf(name, LABEL_PREFIX_BC "%s", bc_names[pi]);
 173       emit_asm_label(ctx, name, size, 1);
 174     }
 175     while (rel < ctx->nreloc && ctx->reloc[rel].ofs < stop) {
 176       int n = ctx->reloc[rel].ofs - prev;
 177       if (ctx->mode == BUILD_machasm && ctx->reloc[rel].type != 0) {
 178         emit_asm_reloc_mach(ctx, ctx->code+prev, n,
 179                             ctx->extnames[ctx->reloc[rel].sym]);
 180       } else {
 181         emit_asm_bytes(ctx, ctx->code+prev, n);
 182         emit_asm_reloc(ctx, &ctx->reloc[rel]);
 183       }
 184       prev += n+4;
 185       rel++;
 186     }
 187     emit_asm_bytes(ctx, ctx->code+prev, stop-prev);
 188     prev = next;
 189     pi = ni;
 190   }
 191
 192   switch (ctx->mode) {
 193   case BUILD_elfasm:
 194     fprintf(ctx->fp, "\n\t.section .rodata\n");
 195     break;
 196   case BUILD_coffasm:
 197     fprintf(ctx->fp, "\n\t.section .rdata,\"dr\"\n");
 198     break;
 199   case BUILD_machasm:
 200     fprintf(ctx->fp, "\n\t.const\n");
 201     break;
 202   default:
 203     break;
 204   }
 205   emit_asm_align(ctx, 5);
 206
 207   emit_asm_label(ctx, LABEL_OP_OFS, 2*ctx->npc, 0);
 208   for (i = 0; i < ctx->npc; i++)
 209     fprintf(ctx->fp, "\t.short %d\n", ctx->sym_ofs[i]);
 210
 211   fprintf(ctx->fp, "\n");
 212   switch (ctx->mode) {
 213   case BUILD_elfasm:
 214     fprintf(ctx->fp, "\t.section .note.GNU-stack,\"\",@progbits\n");
 215     /* fallthrough */
 216   case BUILD_coffasm:
 217     fprintf(ctx->fp, "\t.ident \"%s\"\n", ctx->dasm_ident);
 218     break;
 219   case BUILD_machasm:
 220     fprintf(ctx->fp,
 221       "\t.cstring\n"
 222       "\t.ascii \"%s\\0\"\n", ctx->dasm_ident);
 223     break;
 224   default:
 225     break;
 226   }
 227   fprintf(ctx->fp, "\n");
 228 }
 229