macos: Create symtab
this creates a proper LC_SYMTAB, with reasonable entries. It's
not sorted, so not usable for LC_DYSYMTAB. But 'nm -x -no-sort'
allows to see us some useful info.
This also relocates sections and symbols, so now this example
works as well (i.e. read access to static local data):
% cat simple2.c
static int loc = 42;
int main(void)
{
return loc - 42;
}
This commit is contained in:
Michael Matz
parent
94066765ed
commit
1320d85742
1 changed files with 118 additions and 9 deletions
127
tccmacho.c
127
tccmacho.c
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@ -194,6 +194,14 @@ enum skind {
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sk_last
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};
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struct nlist_64 {
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uint32_t n_strx; /* index into the string table */
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uint8_t n_type; /* type flag, see below */
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uint8_t n_sect; /* section number or NO_SECT */
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uint16_t n_desc; /* see <mach-o/stab.h> */
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uint64_t n_value; /* value of this symbol (or stab offset) */
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};
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struct macho {
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struct mach_header_64 mh;
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struct segment_command_64 *seg[4];
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@ -205,7 +213,8 @@ struct macho {
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Section *s;
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int machosect;
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} sk_to_sect[sk_last];
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Section *linkedit, *wdata;
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int *elfsectomacho;
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Section *linkedit, *symtab, *strtab, *wdata;
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};
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#define SHT_LINKEDIT (SHT_LOOS + 42)
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@ -282,20 +291,22 @@ static void * add_dylib(struct macho *mo, char *name)
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static int check_symbols(TCCState *s1)
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{
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ElfW(Sym) *sym;
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int sym_index, sym_end;
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int ret = 0;
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sym_end = symtab_section->data_offset / sizeof(ElfW(Sym));
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for (sym_index = 1; sym_index < sym_end; ++sym_index) {
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ElfW(Sym) *sym = (ElfW(Sym) *)symtab_section->data + sym_index;
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const char *name = (char*)symtab_section->link->data + sym->st_name;
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unsigned type = ELFW(ST_TYPE)(sym->st_info);
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unsigned bind = ELFW(ST_BIND)(sym->st_info);
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unsigned vis = ELFW(ST_VISIBILITY)(sym->st_other);
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sym = (ElfW(Sym) *)symtab_section->data + sym_index;
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printf("%4d: %09llx %4d %4d %4d %3d %s\n",
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sym_index, sym->st_value,
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type, bind, vis, sym->st_shndx, name);
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if (sym->st_shndx == SHN_UNDEF) {
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const char *name = (char*)symtab_section->link->data + sym->st_name;
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//unsigned type = ELFW(ST_TYPE)(sym->st_info);
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if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
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/* STB_WEAK undefined symbols are accepted */
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continue;
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tcc_error_noabort("undefined symbol '%s'", name);
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ret = -1;
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@ -304,6 +315,75 @@ static int check_symbols(TCCState *s1)
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return ret;
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}
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static void convert_symbol(TCCState *s1, struct macho *mo, struct nlist_64 *pn, ElfSym *sym)
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{
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struct nlist_64 n = *pn;
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const char *name = (char*)symtab_section->link->data + sym->st_name;
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if (sym != (ElfW(Sym) *)symtab_section->data + pn->n_value)
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tcc_error("blaeh");
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switch(ELFW(ST_TYPE)(sym->st_info)) {
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case STT_NOTYPE:
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case STT_OBJECT:
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case STT_FUNC:
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n.n_type = 0xe; /* default type is N_SECT */
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break;
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case STT_FILE:
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n.n_type = 2; /* N_ABS */
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break;
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default:
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tcc_error("unhandled ELF symbol type %d %s",
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ELFW(ST_TYPE)(sym->st_info), name);
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}
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if (sym->st_shndx == SHN_UNDEF)
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n.n_type = 0 /* N_UNDF */, n.n_sect = 0;
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else if (sym->st_shndx == SHN_ABS)
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n.n_type = 2 /* N_ABS */, n.n_sect = 0;
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else if (sym->st_shndx >= SHN_LORESERVE)
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tcc_error("unhandled ELF symbol section %d %s", sym->st_shndx, name);
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else if (!mo->elfsectomacho[sym->st_shndx])
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tcc_error("ELF section %d not mapped into Mach-O for symbol %s",
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sym->st_shndx, name);
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else
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n.n_sect = mo->elfsectomacho[sym->st_shndx];
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if (ELFW(ST_BIND)(sym->st_info) == STB_GLOBAL)
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n.n_type |= 1; /* N_EXT */
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else if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
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tcc_error("weak symbol %s unhandled", name);
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n.n_strx = pn->n_strx;
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n.n_value = sym->st_value;
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*pn = n;
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}
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static void convert_symbols(TCCState *s1, struct macho *mo)
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{
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int sym_index, sym_end;
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struct nlist_64 *pn = (struct nlist_64 *)mo->symtab->data;
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sym_end = symtab_section->data_offset / sizeof(ElfW(Sym));
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for (sym_index = 1; sym_index < sym_end; ++sym_index) {
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ElfW(Sym) *sym = (ElfW(Sym) *)symtab_section->data + sym_index;
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convert_symbol(s1, mo, pn + sym_index - 1, sym);
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}
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}
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static void create_symtab(TCCState *s1, struct macho *mo)
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{
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int sym_index, sym_end;
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struct nlist_64 *pn;
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mo->symtab = new_section(s1, "LESYMTAB", SHT_LINKEDIT, SHF_ALLOC | SHF_WRITE);
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mo->strtab = new_section(s1, "LESTRTAB", SHT_LINKEDIT, SHF_ALLOC | SHF_WRITE);
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put_elf_str(mo->strtab, " "); /* Mach-O start strtab with a space */
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sym_end = symtab_section->data_offset / sizeof(ElfW(Sym));
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pn = section_ptr_add(mo->symtab, sizeof(*pn) * (sym_end - 1));
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for (sym_index = 1; sym_index < sym_end; ++sym_index) {
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ElfW(Sym) *sym = (ElfW(Sym) *)symtab_section->data + sym_index;
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const char *name = (char*)symtab_section->link->data + sym->st_name;
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pn[sym_index - 1].n_strx = put_elf_str(mo->strtab, name);
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pn[sym_index - 1].n_value = sym_index;
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}
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}
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struct {
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int seg;
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uint32_t flags;
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@ -318,7 +398,7 @@ struct {
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static void collect_sections(TCCState *s1, struct macho *mo)
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{
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int i, sk;
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int i, sk, numsec;
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uint64_t curaddr, fileofs;
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Section *s;
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struct segment_command_64 *seg = NULL;
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@ -372,6 +452,9 @@ static void collect_sections(TCCState *s1, struct macho *mo)
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mo->linkedit = new_section(s1, "LINKEDIT", SHT_LINKEDIT, SHF_ALLOC | SHF_WRITE);
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/* LINKEDIT can't be empty (XXX remove once we have symbol table) */
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section_ptr_add(mo->linkedit, 256);
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create_symtab(s1, mo);
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/* dyld requires a writable segment, but ignores zero-sized segments
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for this, so force to have some data. */
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mo->wdata = new_section(s1, " wdata", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
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@ -409,6 +492,8 @@ static void collect_sections(TCCState *s1, struct macho *mo)
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curaddr = mo->seg[1]->vmaddr;
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curaddr += 4096;
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seg = NULL;
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numsec = 0;
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mo->elfsectomacho = tcc_mallocz(sizeof(*mo->elfsectomacho) * s1->nb_sections);
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for (sk = sk_unknown; sk < sk_last; sk++) {
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struct section_64 *sec = NULL;
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if (seg) {
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@ -421,6 +506,7 @@ static void collect_sections(TCCState *s1, struct macho *mo)
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seg = mo->seg[skinfo[sk].seg];
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if (skinfo[sk].name) {
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si = add_section(mo, &seg, skinfo[sk].name);
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numsec++;
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mo->seg[skinfo[sk].seg] = seg;
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mo->sk_to_sect[sk].machosect = si;
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sec = get_section(seg, si);
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@ -462,6 +548,8 @@ static void collect_sections(TCCState *s1, struct macho *mo)
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fileofs += s->sh_size;
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tcc_warning("fileofs now %lld", fileofs);
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}
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if (sec)
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mo->elfsectomacho[s->sh_num] = numsec;
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}
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if (sec)
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sec->size = curaddr - sec->addr;
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@ -490,6 +578,12 @@ static void collect_sections(TCCState *s1, struct macho *mo)
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seg->vmsize = curaddr - seg->vmaddr;
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seg->filesize = fileofs - seg->fileoff;
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}
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/* Fill symtab info */
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symlc->symoff = mo->symtab->sh_offset;
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symlc->nsyms = mo->symtab->data_offset / sizeof(struct nlist_64);
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symlc->stroff = mo->strtab->sh_offset;
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symlc->strsize = mo->strtab->data_offset;
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}
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static void macho_write(TCCState *s1, struct macho *mo, FILE *fp)
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@ -546,7 +640,7 @@ ST_FUNC int macho_output_file(TCCState *s1, const char *filename)
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{
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int fd, mode, file_type;
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FILE *fp;
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int ret = 0;
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int ret = -1;
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struct macho mo = {0,};
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file_type = s1->output_type;
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@ -567,10 +661,25 @@ ST_FUNC int macho_output_file(TCCState *s1, const char *filename)
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resolve_common_syms(s1);
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ret = check_symbols(s1);
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if (!ret) {
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int i;
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Section *s;
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collect_sections(s1, &mo);
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relocate_syms(s1, s1->symtab, 0);
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if (s1->nb_errors)
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goto do_ret;
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for(i = 1; i < s1->nb_sections; i++) {
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s = s1->sections[i];
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if (s->reloc)
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relocate_section(s1, s);
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}
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convert_symbols(s1, &mo);
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macho_write(s1, &mo, fp);
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}
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ret = 0;
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do_ret:
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fclose(fp);
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return ret;
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}
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