outelf32.c

汇编编译器的最新版本的源码.买了自己动手写操作系统这本书的人一定要下

/* outelf.c	output routines for the Netwide Assembler to produce
 *		ELF32 (i386 of course) object file format
 *
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
 * Julian Hall. All rights reserved. The software is
 * redistributable under the license given in the file "LICENSE"
 * distributed in the NASM archive.
 */

#include "compiler.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <inttypes.h>

#include "nasm.h"
#include "nasmlib.h"
#include "saa.h"
#include "raa.h"
#include "stdscan.h"
#include "outform.h"

#ifdef OF_ELF32

/*
 * Relocation types.
 */
enum reloc_type {
    R_386_32 = 1,               /* ordinary absolute relocation */
    R_386_PC32 = 2,             /* PC-relative relocation */
    R_386_GOT32 = 3,            /* an offset into GOT */
    R_386_PLT32 = 4,            /* a PC-relative offset into PLT */
    R_386_COPY = 5,             /* ??? */
    R_386_GLOB_DAT = 6,         /* ??? */
    R_386_JUMP_SLOT = 7,        /* ??? */
    R_386_RELATIVE = 8,         /* ??? */
    R_386_GOTOFF = 9,           /* an offset from GOT base */
    R_386_GOTPC = 10,           /* a PC-relative offset _to_ GOT */
    /* These are GNU extensions, but useful */
    R_386_16 = 20,              /* A 16-bit absolute relocation */
    R_386_PC16 = 21,            /* A 16-bit PC-relative relocation */
    R_386_8 = 22,               /* An 8-bit absolute relocation */
    R_386_PC8 = 23              /* An 8-bit PC-relative relocation */
};

struct Reloc {
    struct Reloc *next;
    int32_t address;               /* relative to _start_ of section */
    int32_t symbol;                /*  symbol index */
    int type;                   /* type of relocation */
};

struct Symbol {
    int32_t strpos;                /* string table position of name */
    int32_t section;               /* section ID of the symbol */
    int type;                   /* symbol type */
    int other;                     /* symbol visibility */
    int32_t value;                 /* address, or COMMON variable align */
    int32_t size;                  /* size of symbol */
    int32_t globnum;               /* symbol table offset if global */
    struct Symbol *next;        /* list of globals in each section */
    struct Symbol *nextfwd;     /* list of unresolved-size symbols */
    char *name;                 /* used temporarily if in above list */
};

#define SHT_PROGBITS 1
#define SHT_NOBITS 8

#define SHF_WRITE 1
#define SHF_ALLOC 2
#define SHF_EXECINSTR 4

struct Section {
    struct SAA *data;
    uint32_t len, size, nrelocs;
    int32_t index;
    int type;                   /* SHT_PROGBITS or SHT_NOBITS */
    int align;                  /* alignment: power of two */
    uint32_t flags;        /* section flags */
    char *name;
    struct SAA *rel;
    int32_t rellen;
    struct Reloc *head, **tail;
    struct Symbol *gsyms;       /* global symbols in section */
};

#define SECT_DELTA 32
static struct Section **sects;
static int nsects, sectlen;

#define SHSTR_DELTA 256
static char *shstrtab;
static int shstrtablen, shstrtabsize;

static struct SAA *syms;
static uint32_t nlocals, nglobs;

static int32_t def_seg;

static struct RAA *bsym;

static struct SAA *strs;
static uint32_t strslen;

static FILE *elffp;
static efunc error;
static evalfunc evaluate;

static struct Symbol *fwds;

static char elf_module[FILENAME_MAX];

static uint8_t elf_osabi = 0;	/* Default OSABI = 0 (System V or Linux) */
static uint8_t elf_abiver = 0;	/* Current ABI version */

extern struct ofmt of_elf32;
extern struct ofmt of_elf;

#define SHN_ABS 0xFFF1
#define SHN_COMMON 0xFFF2
#define SHN_UNDEF 0

#define SYM_GLOBAL 0x10

#define SHT_RELA	  4		/* Relocation entries with addends */

#define STT_NOTYPE	0		/* Symbol type is unspecified */
#define STT_OBJECT	1		/* Symbol is a data object */
#define STT_FUNC	2		/* Symbol is a code object */
#define STT_SECTION	3		/* Symbol associated with a section */
#define STT_FILE	4		/* Symbol's name is file name */
#define STT_COMMON	5		/* Symbol is a common data object */
#define STT_TLS		6		/* Symbol is thread-local data object*/
#define	STT_NUM		7		/* Number of defined types.  */

#define STV_DEFAULT 0
#define STV_INTERNAL 1
#define STV_HIDDEN 2
#define STV_PROTECTED 3

#define GLOBAL_TEMP_BASE 1048576     /* bigger than any reasonable sym id */

#define SEG_ALIGN 16            /* alignment of sections in file */
#define SEG_ALIGN_1 (SEG_ALIGN-1)

/* Definitions in lieu of dwarf.h */
#define    DW_TAG_compile_unit   0x11
#define    DW_TAG_subprogram   0x2e
#define    DW_AT_name   0x03
#define    DW_AT_stmt_list   0x10
#define    DW_AT_low_pc   0x11
#define    DW_AT_high_pc   0x12
#define    DW_AT_language  0x13
#define    DW_AT_producer   0x25
#define    DW_AT_frame_base   0x40
#define    DW_FORM_addr   0x01
#define    DW_FORM_data2   0x05
#define    DW_FORM_data4   0x06
#define    DW_FORM_string   0x08
#define    DW_LNS_extended_op  0
#define    DW_LNS_advance_pc   2
#define    DW_LNS_advance_line   3
#define    DW_LNS_set_file   4
#define    DW_LNE_end_sequence   1
#define    DW_LNE_set_address   2
#define    DW_LNE_define_file   3
#define    DW_LANG_Mips_Assembler  0x8001

#define SOC(ln,aa) ln - line_base + (line_range * aa) + opcode_base

static const char align_str[SEG_ALIGN] = "";    /* ANSI will pad this with 0s */

static struct ELF_SECTDATA {
    void *data;
    int32_t len;
    bool is_saa;
} *elf_sects;
static int elf_nsect, nsections;
static int32_t elf_foffs;

static void elf_write(void);
static void elf_sect_write(struct Section *, const uint8_t *,
                           uint32_t);
static void elf_section_header(int, int, int, void *, bool, int32_t, int, int,
                               int, int);
static void elf_write_sections(void);
static struct SAA *elf_build_symtab(int32_t *, int32_t *);
static struct SAA *elf_build_reltab(int32_t *, struct Reloc *);
static void add_sectname(char *, char *);

/* this stuff is needed for the stabs debugging format */
#define N_SO 0x64               /* ID for main source file */
#define N_SOL 0x84              /* ID for sub-source file */
#define N_BINCL 0x82
#define N_EINCL 0xA2
#define N_SLINE 0x44
#define TY_STABSSYMLIN 0x40     /* ouch */

struct stabentry {
    uint32_t n_strx;
    uint8_t n_type;
    uint8_t n_other;
    uint16_t n_desc;
    uint32_t n_value;
};

struct erel {
    int offset, info;
};

struct symlininfo {
    int offset;
    int section;                /* section index */
    char *name;                 /* shallow-copied pointer of section name */
};

struct linelist {
    struct symlininfo info;
    int line;
    char *filename;
    struct linelist *next;
    struct linelist *last;
};

struct sectlist {
    struct SAA *psaa;
    int section;
    int line;
    int offset;
    int file;
    struct sectlist *next;
    struct sectlist *last;
};

/* common debug variables */
static int currentline = 1;
static int debug_immcall = 0;

/* stabs debug variables */
static struct linelist *stabslines = 0;
static int numlinestabs = 0;
static char *stabs_filename = 0;
static int symtabsection;
static uint8_t *stabbuf = 0, *stabstrbuf = 0, *stabrelbuf = 0;
static int stablen, stabstrlen, stabrellen;

/* dwarf debug variables */
static struct linelist *dwarf_flist = 0, *dwarf_clist = 0, *dwarf_elist = 0;
static struct sectlist *dwarf_fsect = 0, *dwarf_csect = 0, *dwarf_esect = 0;
static int dwarf_numfiles = 0, dwarf_nsections;
static uint8_t *arangesbuf = 0, *arangesrelbuf = 0, *pubnamesbuf = 0, *infobuf = 0,  *inforelbuf = 0,
               *abbrevbuf = 0, *linebuf = 0, *linerelbuf = 0, *framebuf = 0, *locbuf = 0;
static int8_t line_base = -5, line_range = 14, opcode_base = 13;
static int arangeslen, arangesrellen, pubnameslen, infolen, inforellen,
           abbrevlen, linelen, linerellen, framelen, loclen;
static int32_t dwarf_infosym, dwarf_abbrevsym, dwarf_linesym;

static struct dfmt df_dwarf;
static struct dfmt df_stabs;
static struct Symbol *lastsym;

/* common debugging routines */
void debug32_typevalue(int32_t);
void debug32_init(struct ofmt *, void *, FILE *, efunc);
void debug32_deflabel(char *, int32_t, int64_t, int, char *);
void debug32_directive(const char *, const char *);

/* stabs debugging routines */
void stabs32_linenum(const char *filename, int32_t linenumber, int32_t);
void stabs32_output(int, void *);
void stabs32_generate(void);
void stabs32_cleanup(void);

/* dwarf debugging routines */
void dwarf32_linenum(const char *filename, int32_t linenumber, int32_t);
void dwarf32_output(int, void *);
void dwarf32_generate(void);
void dwarf32_cleanup(void);
void dwarf32_findfile(const char *);
void dwarf32_findsect(const int);
void saa_wleb128u(struct SAA *, int);
void saa_wleb128s(struct SAA *, int);

/*
 * Special section numbers which are used to define ELF special
 * symbols, which can be used with WRT to provide PIC relocation
 * types.
 */
static int32_t elf_gotpc_sect, elf_gotoff_sect;
static int32_t elf_got_sect, elf_plt_sect;
static int32_t elf_sym_sect;

static void elf_init(FILE * fp, efunc errfunc, ldfunc ldef, evalfunc eval)
{
    if (of_elf.current_dfmt != &null_debug_form)
        of_elf32.current_dfmt = of_elf.current_dfmt;
    elffp = fp;
    error = errfunc;
    evaluate = eval;
    (void)ldef;                 /* placate optimisers */
    sects = NULL;
    nsects = sectlen = 0;
    syms = saa_init((int32_t)sizeof(struct Symbol));
    nlocals = nglobs = 0;
    bsym = raa_init();
    strs = saa_init(1L);
    saa_wbytes(strs, "\0", 1L);
    saa_wbytes(strs, elf_module, strlen(elf_module)+1);
    strslen = 2 + strlen(elf_module);
    shstrtab = NULL;
    shstrtablen = shstrtabsize = 0;;
    add_sectname("", "");

    fwds = NULL;

    elf_gotpc_sect = seg_alloc();
    ldef("..gotpc", elf_gotpc_sect + 1, 0L, NULL, false, false, &of_elf32,
         error);
    elf_gotoff_sect = seg_alloc();
    ldef("..gotoff", elf_gotoff_sect + 1, 0L, NULL, false, false, &of_elf32,
         error);
    elf_got_sect = seg_alloc();
    ldef("..got", elf_got_sect + 1, 0L, NULL, false, false, &of_elf32,
         error);
    elf_plt_sect = seg_alloc();
    ldef("..plt", elf_plt_sect + 1, 0L, NULL, false, false, &of_elf32,
         error);
    elf_sym_sect = seg_alloc();
    ldef("..sym", elf_sym_sect + 1, 0L, NULL, false, false, &of_elf32,
         error);

    def_seg = seg_alloc();
}

static void elf_cleanup(int debuginfo)
{
    struct Reloc *r;
    int i;

    (void)debuginfo;

    elf_write();
    fclose(elffp);
    for (i = 0; i < nsects; i++) {
        if (sects[i]->type != SHT_NOBITS)
            saa_free(sects[i]->data);
        if (sects[i]->head)
            saa_free(sects[i]->rel);
        while (sects[i]->head) {
            r = sects[i]->head;
            sects[i]->head = sects[i]->head->next;
            nasm_free(r);
        }
    }
    nasm_free(sects);
    saa_free(syms);
    raa_free(bsym);
    saa_free(strs);
    if (of_elf32.current_dfmt) {
        of_elf32.current_dfmt->cleanup();
    }
}

static void add_sectname(char *firsthalf, char *secondhalf)
{
    int len = strlen(firsthalf) + strlen(secondhalf);
    while (shstrtablen + len + 1 > shstrtabsize)
        shstrtab = nasm_realloc(shstrtab, (shstrtabsize += SHSTR_DELTA));
    strcpy(shstrtab + shstrtablen, firsthalf);
    strcat(shstrtab + shstrtablen, secondhalf);
    shstrtablen += len + 1;
}

static int elf_make_section(char *name, int type, int flags, int align)
{
    struct Section *s;

    s = nasm_malloc(sizeof(*s));

    if (type != SHT_NOBITS)
        s->data = saa_init(1L);
    s->head = NULL;
    s->tail = &s->head;
    s->len = s->size = 0;
    s->nrelocs = 0;
    if (!strcmp(name, ".text"))
        s->index = def_seg;
    else
        s->index = seg_alloc();
    add_sectname("", name);
    s->name = nasm_malloc(1 + strlen(name));
    strcpy(s->name, name);
    s->type = type;
    s->flags = flags;
    s->align = align;
    s->gsyms = NULL;