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ELF: eliminate hard-coded section numbers

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Eliminiate hard-coded section numbers, at least to the best of our
ability.  There is still a very odd piece of computation in
elf_build_reltab() which I can't really figure out...

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2009-06-25 14:54:44 -07:00
parent 1acf6ba822
commit c4471462dc
4 changed files with 146 additions and 81 deletions
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3
doc/changes.src
View file

@ -46,6 +46,9 @@ since 2007.
\b The ELF backends no longer automatically generate a \c{.comment} section.
\b Add additional "well-known" ELF sections with default attributes. See
\k{elfsect}.
\S{cl-2.05.01} Version 2.05.01

29
output/outelf.h
View file

@ -31,4 +31,33 @@ struct elf_known_section {
};
extern const struct elf_known_section elf_known_sections[];
/*
* Special ELF sections (after the real sections but before debugging ones)
*/
#define sec_shstrtab (nsects + 1)
#define sec_symtab (nsects + 2)
#define sec_strtab (nsects + 3)
#define sec_numspecial 3
/*
* Debugging ELF sections (last in the file)
*/
/* stabs */
#define sec_stab (nsections-3)
#define sec_stabstr (nsections-2)
#define sec_rel_stab (nsections-1)
/* dwarf */
#define sec_debug_aranges (nsections-10)
#define sec_rela_debug_aranges (nsections-9)
#define sec_debug_pubnames (nsections-8)
#define sec_debug_info (nsections-7)
#define sec_rela_debug_info (nsections-6)
#define sec_debug_abbrev (nsections-5)
#define sec_debug_line (nsections-4)
#define sec_rela_debug_line (nsections-3)
#define sec_debug_frame (nsections-2)
#define sec_debug_loc (nsections-1)
#endif /* OUTPUT_OUTELF_H */

113
output/outelf32.c
View file

@ -162,7 +162,6 @@ static int debug_immcall = 0;
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;
@ -204,7 +203,7 @@ void saa_wleb128u(struct SAA *, int);
void saa_wleb128s(struct SAA *, int);
/*
* Special section numbers which are used to define ELF special
* Special NASM section numbers which are used to define ELF special
* symbols, which can be used with WRT to provide PIC and TLS
* relocation types.
*/
@ -326,8 +325,7 @@ static int elf_make_section(char *name, int type, int flags, int align)
s->gsyms = NULL;
if (nsects >= sectlen)
sects =
nasm_realloc(sects, (sectlen += SECT_DELTA) * sizeof(*sects));
sects = nasm_realloc(sects, (sectlen += SECT_DELTA) * sizeof(*sects));
sects[nsects++] = s;
return nsects - 1;
@ -940,7 +938,6 @@ static void elf_out(int32_t segto, const void *data,
static void elf_write(void)
{
int align;
int scount;
char *p;
int i;
@ -953,7 +950,7 @@ static void elf_write(void)
* `.shstrtab', `.symtab' and `.strtab', then optionally
* relocation sections for the user sections.
*/
nsections = 4;
nsections = sec_numspecial + 1;
if (of_elf32.current_dfmt == &df_stabs)
nsections += 3;
else if (of_elf32.current_dfmt == &df_dwarf)
@ -975,16 +972,10 @@ static void elf_write(void)
add_sectname("", ".stab");
add_sectname("", ".stabstr");
add_sectname(".rel", ".stab");
}
else if (of_elf32.current_dfmt == &df_dwarf) {
} else if (of_elf32.current_dfmt == &df_dwarf) {
/* the dwarf debug standard specifies the following ten sections,
not all of which are currently implemented,
although all of them are defined. */
#define debug_aranges (int32_t) (nsections-10)
#define debug_info (int32_t) (nsections-7)
#define debug_abbrev (int32_t) (nsections-5)
#define debug_line (int32_t) (nsections-4)
add_sectname("", ".debug_aranges");
add_sectname(".rela", ".debug_aranges");
add_sectname("", ".debug_pubnames");
@ -1010,15 +1001,15 @@ static void elf_write(void)
fwriteint32_t(0L, elffp); /* no entry point */
fwriteint32_t(0L, elffp); /* no program header table */
fwriteint32_t(0x40L, elffp); /* section headers straight after
* ELF header plus alignment */
* ELF header plus alignment */
fwriteint32_t(0L, elffp); /* 386 defines no special flags */
fwriteint16_t(0x34, elffp); /* size of ELF header */
fwriteint16_t(0, elffp); /* no program header table, again */
fwriteint16_t(0, elffp); /* still no program header table */
fwriteint16_t(0x28, elffp); /* size of section header */
fwriteint16_t(nsections, elffp); /* number of sections */
fwriteint16_t(nsects + 2, elffp); /* string table section index for
* section header table */
fwriteint16_t(sec_shstrtab, elffp); /* string table section index for
* section header table */
fwriteint32_t(0L, elffp); /* align to 0x40 bytes */
fwriteint32_t(0L, elffp);
fwriteint32_t(0L, elffp);
@ -1042,30 +1033,43 @@ static void elf_write(void)
elf_nsect = 0;
elf_sects = nasm_malloc(sizeof(*elf_sects) * nsections);
elf_section_header(0, 0, 0, NULL, false, 0L, 0, 0, 0, 0); /* SHN_UNDEF */
scount = 1; /* needed for the stabs debugging to track the symtable section */
/* SHN_UNDEF */
elf_section_header(0, SHT_NULL, 0, NULL, false, 0, SHN_UNDEF, 0, 0, 0);
p = shstrtab + 1;
/* The normal sections */
for (i = 0; i < nsects; i++) {
elf_section_header(p - shstrtab, sects[i]->type, sects[i]->flags,
(sects[i]->type == SHT_PROGBITS ?
sects[i]->data : NULL), true,
sects[i]->len, 0, 0, sects[i]->align, 0);
p += strlen(p) + 1;
scount++; /* dito */
}
elf_section_header(p - shstrtab, 3, 0, shstrtab, false, (int32_t)shstrtablen, 0, 0, 1, 0); /* .shstrtab */
scount++; /* dito */
/* .shstrtab */
elf_section_header(p - shstrtab, SHT_STRTAB, 0, shstrtab, false,
shstrtablen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 2, 0, symtab, true, symtablen, nsects + 4, symtablocal, 4, 16); /* .symtab */
symtabsection = scount; /* now we got the symtab section index in the ELF file */
/* .symtab */
elf_section_header(p - shstrtab, SHT_SYMTAB, 0, symtab, true,
symtablen, sec_strtab, symtablocal, 4, 16);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 3, 0, strs, true, strslen, 0, 0, 1, 0); /* .strtab */
/* .strtab */
elf_section_header(p - shstrtab, SHT_STRTAB, 0, strs, true,
strslen, 0, 0, 1, 0);
p += strlen(p) + 1;
/* The relocation sections */
for (i = 0; i < nsects; i++)
if (sects[i]->head) {
elf_section_header(p - shstrtab, SHT_REL, 0, sects[i]->rel, true,
sects[i]->rellen, sec_symtab, i + 1, 4, 8);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 9, 0, sects[i]->rel, true,
sects[i]->rellen, nsects + 3, i + 1, 4, 8);
}
if (of_elf32.current_dfmt == &df_stabs) {
/* for debugging information, create the last three sections
which are the .stab , .stabstr and .rel.stab sections respectively */
@ -1073,59 +1077,67 @@ static void elf_write(void)
/* this function call creates the stab sections in memory */
stabs32_generate();
if ((stabbuf) && (stabstrbuf) && (stabrelbuf)) {
if (stabbuf && stabstrbuf && stabrelbuf) {
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, stabbuf, false,
stablen, sec_stabstr, 0, 4, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 1, 0, stabbuf, false, stablen,
nsections - 2, 0, 4, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 3, 0, stabstrbuf, false,
elf_section_header(p - shstrtab, SHT_STRTAB, 0, stabstrbuf, false,
stabstrlen, 0, 0, 4, 0);
p += strlen(p) + 1;
/* link -> symtable info -> section to refer to */
elf_section_header(p - shstrtab, 9, 0, stabrelbuf, false,
stabrellen, symtabsection, nsections - 3, 4,
8);
elf_section_header(p - shstrtab, SHT_REL, 0, stabrelbuf, false,
stabrellen, sec_symtab, sec_stab, 4, 8);
p += strlen(p) + 1;
}
}
else if (of_elf32.current_dfmt == &df_dwarf) {
} else if (of_elf32.current_dfmt == &df_dwarf) {
/* for dwarf debugging information, create the ten dwarf sections */
/* this function call creates the dwarf sections in memory */
if (dwarf_fsect) dwarf32_generate();
if (dwarf_fsect)
dwarf32_generate();
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, arangesbuf, false,
arangeslen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_RELA, 0, arangesrelbuf, false,
arangesrellen, symtabsection, debug_aranges, 1, 12);
arangesrellen, sec_symtab, sec_debug_aranges,
1, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, pubnamesbuf, false,
pubnameslen, 0, 0, 1, 0);
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, pubnamesbuf,
false, pubnameslen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, infobuf, false,
infolen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_RELA, 0, inforelbuf, false,
inforellen, symtabsection, debug_info, 1, 12);
inforellen, sec_symtab, sec_debug_info, 1, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, abbrevbuf, false,
abbrevlen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, linebuf, false,
linelen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_RELA, 0, linerelbuf, false,
linerellen, symtabsection, debug_line, 1, 12);
linerellen, sec_symtab, sec_debug_line, 1, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, framebuf, false,
framelen, 0, 0, 8, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, locbuf, false,
loclen, 0, 0, 1, 0);
p += strlen(p) + 1;
}
fwritezero(align, elffp);
@ -1213,7 +1225,7 @@ static struct SAA *elf_build_symtab(int32_t *len, int32_t *local)
WRITELONG(p, (uint32_t) 0); /* offset zero */
WRITELONG(p, (uint32_t) 0); /* size zero */
WRITESHORT(p, STT_SECTION); /* type, binding, and visibility */
WRITESHORT(p, debug_info); /* section id */
WRITESHORT(p, sec_debug_info); /* section id */
saa_wbytes(s, entry, 16L);
*len += 16;
(*local)++;
@ -1223,7 +1235,7 @@ static struct SAA *elf_build_symtab(int32_t *len, int32_t *local)
WRITELONG(p, (uint32_t) 0); /* offset zero */
WRITELONG(p, (uint32_t) 0); /* size zero */
WRITESHORT(p, STT_SECTION); /* type, binding, and visibility */
WRITESHORT(p, debug_abbrev); /* section id */
WRITESHORT(p, sec_debug_abbrev); /* section id */
saa_wbytes(s, entry, 16L);
*len += 16;
(*local)++;
@ -1233,7 +1245,7 @@ static struct SAA *elf_build_symtab(int32_t *len, int32_t *local)
WRITELONG(p, (uint32_t) 0); /* offset zero */
WRITELONG(p, (uint32_t) 0); /* size zero */
WRITESHORT(p, STT_SECTION); /* type, binding, and visibility */
WRITESHORT(p, debug_line); /* section id */
WRITESHORT(p, sec_debug_line); /* section id */
saa_wbytes(s, entry, 16L);
*len += 16;
(*local)++;
@ -1277,8 +1289,9 @@ static struct SAA *elf_build_reltab(int32_t *len, struct Reloc *r)
if (sym >= GLOBAL_TEMP_BASE)
{
if (of_elf32.current_dfmt == &df_dwarf)
sym += -GLOBAL_TEMP_BASE + (nsects + 5) + nlocals;
else sym += -GLOBAL_TEMP_BASE + (nsects + 2) + nlocals;
sym += -GLOBAL_TEMP_BASE + (nsects + 5) + nlocals;
else
sym += -GLOBAL_TEMP_BASE + (nsects + 2) + nlocals;
}
p = entry;

82
output/outelf64.c
View file

@ -56,7 +56,7 @@ struct Section {
uint64_t len, size;
uint32_t nrelocs;
int32_t index; /* index into sects array */
uint32_t type; /* SHT_PROGBITS or SHT_NOBITS */
int type; /* SHT_PROGBITS or SHT_NOBITS */
uint64_t align; /* alignment: power of two */
uint64_t flags; /* section flags */
char *name;
@ -326,8 +326,7 @@ static int elf_make_section(char *name, int type, int flags, int align)
s->gsyms = NULL;
if (nsects >= sectlen)
sects =
nasm_realloc(sects, (sectlen += SECT_DELTA) * sizeof(*sects));
sects = nasm_realloc(sects, (sectlen += SECT_DELTA) * sizeof(*sects));
sects[nsects++] = s;
return nsects - 1;
@ -1023,7 +1022,6 @@ static void elf_out(int32_t segto, const void *data,
static void elf_write(void)
{
int align;
int scount;
char *p;
int i;
@ -1036,7 +1034,7 @@ static void elf_write(void)
* `.shstrtab', `.symtab' and `.strtab', then optionally
* relocation sections for the user sections.
*/
nsections = 4;
nsections = sec_numspecial + 1;
if (of_elf64.current_dfmt == &df_stabs)
nsections += 3;
else if (of_elf64.current_dfmt == &df_dwarf)
@ -1100,8 +1098,8 @@ static void elf_write(void)
fwriteint16_t(0, elffp); /* still no program header table */
fwriteint16_t(sizeof(Elf64_Shdr), elffp); /* size of section header */
fwriteint16_t(nsections, elffp); /* number of sections */
fwriteint16_t(nsects + 2, elffp); /* string table section index for
* section header table */
fwriteint16_t(sec_shstrtab, elffp); /* string table section index for
* section header table */
/*
* Build the symbol table and relocation tables.
@ -1121,30 +1119,43 @@ static void elf_write(void)
elf_foffs += align;
elf_nsect = 0;
elf_sects = nasm_malloc(sizeof(*elf_sects) * nsections);
elf_section_header(0, 0, 0, NULL, false, 0L, 0, 0, 0, 0); /* SHN_UNDEF */
scount = 1; /* needed for the stabs debugging to track the symtable section */
/* SHN_UNDEF */
elf_section_header(0, SHT_NULL, 0, NULL, false, 0, SHN_UNDEF, 0, 0, 0);
p = shstrtab + 1;
/* The normal sections */
for (i = 0; i < nsects; i++) {
elf_section_header(p - shstrtab, sects[i]->type, sects[i]->flags,
(sects[i]->type == SHT_PROGBITS ?
sects[i]->data : NULL), true,
sects[i]->len, 0, 0, sects[i]->align, 0);
p += strlen(p) + 1;
scount++; /* ditto */
}
elf_section_header(p - shstrtab, 3, 0, shstrtab, false, (int32_t)shstrtablen, 0, 0, 1, 0); /* .shstrtab */
scount++; /* ditto */
/* .shstrtab */
elf_section_header(p - shstrtab, SHT_STRTAB, 0, shstrtab, false,
shstrtablen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 2, 0, symtab, true, symtablen, nsects + 4, symtablocal, 4, 24); /* .symtab */
symtabsection = scount; /* now we got the symtab section index in the ELF file */
/* .symtab */
elf_section_header(p - shstrtab, SHT_SYMTAB, 0, symtab, true,
symtablen, sec_strtab, symtablocal, 4, 24);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 3, 0, strs, true, strslen, 0, 0, 1, 0); /* .strtab */
/* .strtab */
elf_section_header(p - shstrtab, SHT_SYMTAB, 0, strs, true,
strslen, 0, 0, 1, 0);
p += strlen(p) + 1;
/* The relocation sections */
for (i = 0; i < nsects; i++)
if (sects[i]->head) {
elf_section_header(p - shstrtab, SHT_RELA, 0, sects[i]->rel, true,
sects[i]->rellen, sec_symtab, i + 1, 4, 24);
p += strlen(p) + 1;
elf_section_header(p - shstrtab,SHT_RELA, 0, sects[i]->rel, true,
sects[i]->rellen, nsects + 3, i + 1, 4, 24);
}
if (of_elf64.current_dfmt == &df_stabs) {
/* for debugging information, create the last three sections
which are the .stab , .stabstr and .rel.stab sections respectively */
@ -1152,59 +1163,67 @@ static void elf_write(void)
/* this function call creates the stab sections in memory */
stabs64_generate();
if ((stabbuf) && (stabstrbuf) && (stabrelbuf)) {
if (stabbuf && stabstrbuf && stabrelbuf) {
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, stabbuf, false,
stablen, sec_stabstr, 0, 4, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 1, 0, stabbuf, false, stablen,
nsections - 2, 0, 4, 12);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, 3, 0, stabstrbuf, false,
elf_section_header(p - shstrtab, SHT_STRTAB, 0, stabstrbuf, false,
stabstrlen, 0, 0, 4, 0);
p += strlen(p) + 1;
/* link -> symtable info -> section to refer to */
elf_section_header(p - shstrtab, 9, 0, stabrelbuf, false,
stabrellen, symtabsection, nsections - 3, 4,
16);
elf_section_header(p - shstrtab, SHT_REL, 0, stabrelbuf, false,
stabrellen, symtabsection, sec_stab, 4, 16);
p += strlen(p) + 1;
}
}
else if (of_elf64.current_dfmt == &df_dwarf) {
/* for dwarf debugging information, create the ten dwarf sections */
/* this function call creates the dwarf sections in memory */
if (dwarf_fsect) dwarf64_generate();
if (dwarf_fsect)
dwarf64_generate();
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, arangesbuf, false,
arangeslen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_RELA, 0, arangesrelbuf, false,
arangesrellen, symtabsection, debug_aranges, 1, 24);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, pubnamesbuf, false,
pubnameslen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, infobuf, false,
infolen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_RELA, 0, inforelbuf, false,
inforellen, symtabsection, debug_info, 1, 24);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, abbrevbuf, false,
abbrevlen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, linebuf, false,
linelen, 0, 0, 1, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_RELA, 0, linerelbuf, false,
linerellen, symtabsection, debug_line, 1, 24);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, framebuf, false,
framelen, 0, 0, 8, 0);
p += strlen(p) + 1;
elf_section_header(p - shstrtab, SHT_PROGBITS, 0, locbuf, false,
loclen, 0, 0, 1, 0);
p += strlen(p) + 1;
}
fwritezero(align, elffp);
@ -1356,8 +1375,9 @@ static struct SAA *elf_build_reltab(uint64_t *len, struct Reloc *r)
if (sym >= GLOBAL_TEMP_BASE)
{
if (of_elf64.current_dfmt == &df_dwarf)
sym += -GLOBAL_TEMP_BASE + (nsects + 5) + nlocals;
else sym += -GLOBAL_TEMP_BASE + (nsects + 2) + nlocals;
sym += -GLOBAL_TEMP_BASE + (nsects + 5) + nlocals;
else
sym += -GLOBAL_TEMP_BASE + (nsects + 2) + nlocals;
}
p = entry;
WRITEDLONG(p, r->address);