1
0
mirror of https://github.com/golang/go synced 2024-11-12 07:40:23 -07:00

cmd/5l: generate FreeBSD compatible ELF

1. correctly initialize .plt.got entries (point to the 1st entry)
2. add section .rel.plt (FreeBSD insists PLT relocs to be there)
3. put relocs of .got.plt into .rel.plt
4. set ELFOSABI_FREEBSD in ELF header

R=rsc
CC=golang-dev
https://golang.org/cl/6643050
This commit is contained in:
Shenghou Ma 2012-10-10 01:02:49 +08:00
parent fa563ae82e
commit d901808869
2 changed files with 54 additions and 23 deletions

View File

@ -38,6 +38,7 @@
static Prog *PP;
char linuxdynld[] = "/lib/ld-linux.so.3"; // 2 for OABI, 3 for EABI
char freebsddynld[] = "/usr/libexec/ld-elf.so.1";
int32
entryvalue(void)
@ -344,13 +345,16 @@ addpltsym(Sym *s)
if(iself) {
plt = lookup(".plt", 0);
got = lookup(".got.plt", 0);
rel = lookup(".rel", 0);
rel = lookup(".rel.plt", 0);
if(plt->size == 0)
elfsetupplt();
// .got entry
s->got = got->size;
adduint32(got, 0);
// In theory, all GOT should point to the first PLT entry,
// Linux/ARM's dynamic linker will do that for us, but FreeBSD/ARM's
// dynamic linker won't, so we'd better do it ourselves.
addaddrplus(got, plt, 0);
// .plt entry, this depends on the .got entry
s->plt = plt->size;
@ -696,7 +700,7 @@ asmb(void)
/* !debug['d'] causes extra sections before the .text section */
elftextsh = 2;
if(!debug['d']) {
elftextsh += 9;
elftextsh += 10;
if(elfverneed)
elftextsh += 2;
}
@ -755,6 +759,9 @@ asmb(void)
Bflush(&bso);
cseek(0L);
switch(HEADTYPE) {
default:
if(iself)
goto Elfput;
case Hnoheader: /* no header */
break;
case Hrisc: /* aif for risc os */
@ -815,7 +822,7 @@ asmb(void)
lputl(0xe3300000); /* nop */
lputl(0xe3300000); /* nop */
break;
case Hlinux:
Elfput:
/* elf arm */
eh = getElfEhdr();
fo = HEADR;
@ -851,8 +858,16 @@ asmb(void)
sh->type = SHT_PROGBITS;
sh->flags = SHF_ALLOC;
sh->addralign = 1;
if(interpreter == nil)
interpreter = linuxdynld;
if(interpreter == nil) {
switch(HEADTYPE) {
case Hlinux:
interpreter = linuxdynld;
break;
case Hfreebsd:
interpreter = freebsddynld;
break;
}
}
resoff -= elfinterp(sh, startva, resoff, interpreter);
ph = newElfPhdr();
@ -886,6 +901,31 @@ asmb(void)
/* Dynamic linking sections */
if(!debug['d']) { /* -d suppresses dynamic loader format */
/* S headers for dynamic linking */
dynsym = eh->shnum;
sh = newElfShdr(elfstr[ElfStrDynsym]);
sh->type = SHT_DYNSYM;
sh->flags = SHF_ALLOC;
sh->entsize = ELF32SYMSIZE;
sh->addralign = 4;
sh->link = dynsym+1; // dynstr
// sh->info = index of first non-local symbol (number of local symbols)
shsym(sh, lookup(".dynsym", 0));
sh = newElfShdr(elfstr[ElfStrDynstr]);
sh->type = SHT_STRTAB;
sh->flags = SHF_ALLOC;
sh->addralign = 1;
shsym(sh, lookup(".dynstr", 0));
sh = newElfShdr(elfstr[ElfStrRelPlt]);
sh->type = SHT_REL;
sh->flags = SHF_ALLOC;
sh->entsize = ELF32RELSIZE;
sh->addralign = 4;
sh->link = dynsym;
sh->info = eh->shnum; // .plt
shsym(sh, lookup(".rel.plt", 0));
// ARM ELF needs .plt to be placed before .got
sh = newElfShdr(elfstr[ElfStrPlt]);
sh->type = SHT_PROGBITS;
@ -908,22 +948,6 @@ asmb(void)
sh->addralign = 4;
shsym(sh, lookup(".got", 0));
dynsym = eh->shnum;
sh = newElfShdr(elfstr[ElfStrDynsym]);
sh->type = SHT_DYNSYM;
sh->flags = SHF_ALLOC;
sh->entsize = ELF32SYMSIZE;
sh->addralign = 4;
sh->link = dynsym+1; // dynstr
// sh->info = index of first non-local symbol (number of local symbols)
shsym(sh, lookup(".dynsym", 0));
sh = newElfShdr(elfstr[ElfStrDynstr]);
sh->type = SHT_STRTAB;
sh->flags = SHF_ALLOC;
sh->addralign = 1;
shsym(sh, lookup(".dynstr", 0));
if(elfverneed) {
sh = newElfShdr(elfstr[ElfStrGnuVersion]);
sh->type = SHT_GNU_VERSYM;
@ -1029,6 +1053,11 @@ asmb(void)
eh->ident[EI_CLASS] = ELFCLASS32;
eh->ident[EI_DATA] = ELFDATA2LSB;
eh->ident[EI_VERSION] = EV_CURRENT;
switch(HEADTYPE) {
case Hfreebsd:
eh->ident[EI_OSABI] = ELFOSABI_FREEBSD;
break;
}
eh->type = ET_EXEC;
eh->machine = EM_ARM;

View File

@ -52,6 +52,7 @@ Header headers[] = {
"ixp1200", Hixp1200,
"ipaq", Hipaq,
"linux", Hlinux,
"freebsd", Hfreebsd,
0, 0
};
@ -152,7 +153,7 @@ main(int argc, char *argv[])
libinit();
if(HEADTYPE == -1)
HEADTYPE = Hlinux;
HEADTYPE = headtype(goos);
switch(HEADTYPE) {
default:
diag("unknown -H option");
@ -212,6 +213,7 @@ main(int argc, char *argv[])
INITRND = 1024;
break;
case Hlinux: /* arm elf */
case Hfreebsd:
debug['d'] = 0; // with dynamic linking
tlsoffset = -8; // hardcoded number, first 4-byte word for g, and then 4-byte word for m
// this number is known to ../../pkg/runtime/cgo/gcc_linux_arm.c