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author | lost |
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date | Sat, 17 Jan 2009 07:09:02 +0000 |
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/* output.c Copyright © 2009 William Astle This file is part of LWASM. LWASM is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. Contains the code for actually outputting the assembled code */ //#include <ctype.h> #include <errno.h> #include <stdio.h> //#include <stdlib.h> #include <string.h> #include <unistd.h> #define __output_c_seen__ //#include "instab.h" #include "lwasm.h" #include "util.h" void write_code_raw(asmstate_t *as, FILE *of); void write_code_decb(asmstate_t *as, FILE *of); void write_code_rawrel(asmstate_t *as, FILE *of); void write_code_obj(asmstate_t *as, FILE *of); // this prevents warnings about not using the return value of fwrite() #define writebytes(s, l, c, f) do { int r; r = fwrite((s), (l), (c), (f)); } while (0) void lwasm_output(asmstate_t *as) { FILE *of; if (as -> errorcount > 0) { fprintf(stderr, "Not doing output due to assembly errors.\n"); return; } of = fopen(as -> outfile, "wb"); if (!of) { fprintf(stderr, "Cannot open '%s' for output", as -> outfile); perror(""); return; } switch (as -> outformat) { case OUTPUT_RAW: write_code_raw(as, of); break; case OUTPUT_DECB: write_code_decb(as, of); break; case OUTPUT_RAWREL: write_code_rawrel(as, of); break; case OUTPUT_OBJ: write_code_obj(as, of); break; default: fprintf(stderr, "BUG: unrecognized output format when generating output file\n"); fclose(of); unlink(as -> outfile); return; } fclose(of); } /* rawrel output treats an ORG directive as an offset from the start of the file. Undefined results will occur if an ORG directive moves the output pointer backward. This particular implementation uses "fseek" to handle ORG requests and to skip over RMBs. This simple brain damanged method simply does an fseek before outputting each instruction. */ void write_code_rawrel(asmstate_t *as, FILE *of) { lwasm_line_t *cl; for (cl = as -> lineshead; cl; cl = cl -> next) { if (cl -> codelen == 0) continue; fseek(of, cl -> codeaddr, SEEK_SET); writebytes(cl -> bytes, cl -> codelen, 1, of); } } /* raw merely writes all the bytes directly to the file as is. ORG is just a reference for the assembler to handle absolute references. Multiple ORG statements will produce mostly useless results */ void write_code_raw(asmstate_t *as, FILE *of) { lwasm_line_t *cl; for (cl = as -> lineshead; cl; cl = cl -> next) { if (cl -> nocodelen) { int i; for (i = 0; i < cl -> nocodelen; i++) writebytes("\0", 1, 1, of); continue; } writebytes(cl -> bytes, cl -> codelen, 1, of); } } void write_code_decb(asmstate_t *as, FILE *of) { long preambloc; lwasm_line_t *cl; int blocklen = -1; int nextcalc = -1; unsigned char outbuf[5]; for (cl = as -> lineshead; cl; cl = cl -> next) { if (cl -> nocodelen) continue; if (cl -> codeaddr != nextcalc && cl -> codelen > 0) { // need preamble here if (blocklen > 0) { // update previous preamble if needed fseek(of, preambloc, SEEK_SET); outbuf[0] = (blocklen >> 8) & 0xFF; outbuf[1] = blocklen & 0xFF; writebytes(outbuf, 2, 1, of); fseek(of, 0, SEEK_END); } blocklen = 0; nextcalc = cl -> codeaddr; outbuf[0] = 0x00; outbuf[1] = 0x00; outbuf[2] = 0x00; outbuf[3] = (nextcalc >> 8) & 0xFF; outbuf[4] = nextcalc & 0xFF; preambloc = ftell(of) + 1; writebytes(outbuf, 5, 1, of); } nextcalc += cl -> codelen; writebytes(cl -> bytes, cl -> codelen, 1, of); blocklen += cl -> codelen; } if (blocklen > 0) { fseek(of, preambloc, SEEK_SET); outbuf[0] = (blocklen >> 8) & 0xFF; outbuf[1] = blocklen & 0xFF; writebytes(outbuf, 2, 1, of); fseek(of, 0, SEEK_END); } // now write postamble outbuf[0] = 0xFF; outbuf[1] = 0x00; outbuf[2] = 0x00; outbuf[3] = (as -> execaddr >> 8) & 0xFF; outbuf[4] = (as -> execaddr) & 0xFF; writebytes(outbuf, 5, 1, of); } void write_code_obj_sbadd(sectiontab_t *s, unsigned char b) { if (s -> oblen >= s -> obsize) { s -> obytes = lwasm_realloc(s -> obytes, s -> obsize + 128); s -> obsize += 128; } s -> obytes[s -> oblen] = b; s -> oblen += 1; } void write_code_obj(asmstate_t *as, FILE *of) { lwasm_line_t *l; sectiontab_t *s; lwasm_symbol_ent_t *se; export_list_t *ex; section_reloc_list_t *re; lwasm_expr_stack_node_t *sn; int i; unsigned char buf[16]; // output the magic number and file header // the 8 is NOT an error writebytes("LWOBJ16", 8, 1, of); // run through the entire system and build the byte streams for each // section; at the same time, generate a list of "local" symbols to // output for each section // NOTE: for "local" symbols, we will append \x01 and the ascii string // of the context identifier (so sym in context 1 would be "sym\x011" // we can do this because the linker can handle symbols with any // character other than NUL. // also we will generate a list of incomplete references for each // section along with the actual definition that will be output // once all this information is generated, we will output each section // to the file // NOTE: we build everything in memory then output it because the // assembler accepts multiple instances of the same section but the // linker expects only one instance of each section in the object file // so we need to collect all the various pieces of a section together // (also, the assembler treated multiple instances of the same section // as continuations of previous sections so we would need to collect // them together anyway. for (l = as -> lineshead; l; l = l -> next) { if (l -> sect) { // we're in a section - need to output some bytes for (i = 0; i < l -> codelen; i++) write_code_obj_sbadd(l -> sect, l -> bytes[i]); for (i = 0; i < l -> nocodelen; i++) write_code_obj_sbadd(l -> sect, 0); // do we have a "relocation"? If so, add a reference to the // relocation table if (l -> relocoff >= 0) { // build the relocation reference for the linker re = lwasm_alloc(sizeof(section_reloc_list_t)); re -> next = l -> sect -> rl; l -> sect -> rl = re; re -> offset = l -> codeaddr + l -> relocoff; re -> expr = l -> exprs[0]; re -> context = l -> context; } } } // run through the sections for (s = as -> sections; s; s = s -> next) { // write the name writebytes(s -> name, strlen(s -> name) + 1, 1, of); // write the flags if (s -> flags & SECTION_BSS) writebytes("\x01", 1, 1, of); // indicate end of flags - the "" is NOT an error writebytes("", 1, 1, of); // now the local symbols for (se = as -> symhead; se; se = se -> next) { // ignore symbols not in this section if (se -> sect != s) continue; if (se -> flags & SYMBOL_SET) continue; if (se -> flags & SYMBOL_EXTERN) continue; writebytes(se -> sym, strlen(se -> sym), 1, of); if (se -> context >= 0) { writebytes("\x01", 1, 1, of); sprintf(buf, "%d", se -> context); writebytes(buf, strlen(buf), 1, of); } // the "" is NOT an error writebytes("", 1, 1, of); // write the address buf[0] = (se -> value >> 8) & 0xff; buf[1] = se -> value & 0xff; writebytes(buf, 2, 1, of); } // flag end of local symbol table - "" is NOT an error writebytes("", 1, 1, of); // now the exports for (ex = s -> exports; ex; ex = ex -> next) { writebytes(ex -> sym, strlen(ex -> sym) + 1, 1, of); buf[0] = (ex -> offset >> 8) & 0xff; buf[1] = ex -> offset & 0xff; writebytes(buf, 2, 1, of); } // flag end of exported symbols - "" is NOT an error writebytes("", 1, 1, of); // now output the "incomplete references" // this being the most complex bit for (re = s -> rl; re; re = re -> next) { if (re -> expr == NULL) { // this is an error but we'll simply ignore it // and not output this expression continue; } // work through each term in the expression and output // the proper equivalent to the object file for (sn = re -> expr -> head; sn; sn = sn -> next) { switch (sn -> term -> term_type) { case LWASM_TERM_OPER: buf[0] = 0x04; buf[1] = sn -> term -> value; writebytes(buf, 2, 1, of); break; case LWASM_TERM_INT: buf[0] = 0x01; buf[1] = (sn -> term -> value >> 8) & 0xff; buf[2] = sn -> term -> value & 0xff; writebytes(buf, 3, 1, of); break; case LWASM_TERM_SECBASE: writebytes("\x05", 1, 1, of); break; case LWASM_TERM_SYM: // now for the ugly part - resolve a symbol reference // and determine whether it's internal, external, or // a section base se = lwasm_find_symbol(as, sn -> term -> symbol, re -> context); if (!se) se = lwasm_find_symbol(as, sn -> term -> symbol, -1); if (!se || se -> flags & SYMBOL_EXTERN) { // not found - assume external reference // found but flagged external - handle it writebytes("\x02", 1, 1, of); writebytes(se -> sym, strlen(se -> sym) + 1, 1, of); break; } // a local symbol reference here writebytes("\x03", 1, 1, of); writebytes(se -> sym, strlen(se -> sym), 1, of); if (se -> context >= 0) { writebytes("\x01", 1, 1, of); sprintf(buf, "%d", se -> context); writebytes(buf, strlen(buf), 1, of); } writebytes("", 1, 1, of); break; default: // unrecognized term type - replace with integer 0 buf[0] = 0x01; buf[1] = 0x00; buf[2] = 0x00; writebytes(buf, 3, 1, of); break; } } // flag end of expressions writebytes("", 1, 1, of); // write the offset buf[0] = (re -> offset >> 8) & 0xff; buf[1] = re -> offset & 0xff; writebytes(buf, 2, 1, of); } // flag end of incomplete references list writebytes("", 1, 1, of); // now blast out the code // length buf[0] = s -> oblen >> 8 & 0xff; buf[1] = s -> oblen & 0xff; writebytes(buf, 2, 1, of); if (!(s -> flags & SECTION_BSS)) { writebytes(s -> obytes, s -> oblen, 1, of); } } // flag no more sections // the "" is NOT an error writebytes("", 1, 1, of); }