From: Gustavo Niemeyer Date: Wed, 20 Jul 2011 15:47:02 +0000 (-0300) Subject: ld: remove overlap of ELF sections on dynamic binaries X-Git-Tag: weekly.2011-07-29~117 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ba2e3af1778da52340a9f3f7dd7262e5ebf64055;p=gostls13.git ld: remove overlap of ELF sections on dynamic binaries The dynamic ELF sections were pointing to the proper data, but that data was already owned by the rodata and text sections. Some ELF references explicitly prohibit multiple sections from owning the same data, and strip behaves accordingly. The data for these sections was moved out and their ranges are now owned by their respective sections. This change makes strip happy both with and without -s being provided at link time. A test was added in debug/elf to ensure there are no regressions on this area in the future. Fixes #1242. Fixes #2022. NOTE: Tested on Linux amd64/386/arm only. R=rsc CC=golang-dev https://golang.org/cl/4808043 --- diff --git a/src/cmd/5l/asm.c b/src/cmd/5l/asm.c index b820cc7082..8a60ff74a9 100644 --- a/src/cmd/5l/asm.c +++ b/src/cmd/5l/asm.c @@ -157,7 +157,7 @@ doelf(void) /* predefine strings we need for section headers */ shstrtab = lookup(".shstrtab", 0); - shstrtab->type = SELFDATA; + shstrtab->type = SELFROSECT; shstrtab->reachable = 1; elfstr[ElfStrEmpty] = addstring(shstrtab, ""); @@ -186,19 +186,22 @@ doelf(void) elfstr[ElfStrPlt] = addstring(shstrtab, ".plt"); /* interpreter string */ + if(interpreter == nil) + interpreter = linuxdynld; s = lookup(".interp", 0); + s->type = SELFROSECT; s->reachable = 1; - s->type = SELFDATA; // TODO: rodata + addstring(s, interpreter); /* dynamic symbol table - first entry all zeros */ s = lookup(".dynsym", 0); - s->type = SELFDATA; + s->type = SELFROSECT; s->reachable = 1; s->value += ELF32SYMSIZE; /* dynamic string table */ s = lookup(".dynstr", 0); - s->type = SELFDATA; + s->type = SELFROSECT; s->reachable = 1; if(s->size == 0) addstring(s, ""); @@ -207,37 +210,37 @@ doelf(void) /* relocation table */ s = lookup(".rel", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* global offset table */ s = lookup(".got", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFSECT; // writable /* hash */ s = lookup(".hash", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* got.plt */ s = lookup(".got.plt", 0); s->reachable = 1; - s->type = SDATA; // writable, so not SELFDATA + s->type = SELFSECT; // writable s = lookup(".plt", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".rel.plt", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; elfsetupplt(); /* define dynamic elf table */ s = lookup(".dynamic", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* * .dynamic table @@ -274,8 +277,11 @@ datoff(vlong addr) void shsym(Elf64_Shdr *sh, Sym *s) { - sh->addr = symaddr(s); - sh->off = datoff(sh->addr); + vlong addr; + addr = symaddr(s); + if(sh->flags&SHF_ALLOC) + sh->addr = addr; + sh->off = datoff(addr); sh->size = s->size; } @@ -331,7 +337,7 @@ asmb(void) if(iself) { /* index of elf text section; needed by asmelfsym, double-checked below */ /* !debug['d'] causes extra sections before the .text section */ - elftextsh = 1; + elftextsh = 2; if(!debug['d']) { elftextsh += 10; if(elfverneed) @@ -486,9 +492,7 @@ asmb(void) sh->type = SHT_PROGBITS; sh->flags = SHF_ALLOC; sh->addralign = 1; - if(interpreter == nil) - interpreter = linuxdynld; - elfinterp(sh, startva, interpreter); + shsym(sh, lookup(".interp", 0)); ph = newElfPhdr(); ph->type = PT_INTERP; @@ -579,6 +583,11 @@ asmb(void) ph->flags = PF_W+PF_R; ph->align = 4; + sh = newElfShstrtab(elfstr[ElfStrShstrtab]); + sh->type = SHT_STRTAB; + sh->addralign = 1; + shsym(sh, lookup(".shstrtab", 0)); + if(elftextsh != eh->shnum) diag("elftextsh = %d, want %d", elftextsh, eh->shnum); for(sect=segtext.sect; sect!=nil; sect=sect->next) @@ -604,11 +613,6 @@ asmb(void) // dwarfaddelfheaders(); } - sh = newElfShstrtab(elfstr[ElfStrShstrtab]); - sh->type = SHT_STRTAB; - sh->addralign = 1; - shsym(sh, lookup(".shstrtab", 0)); - /* Main header */ eh->ident[EI_MAG0] = '\177'; eh->ident[EI_MAG1] = 'E'; @@ -634,7 +638,7 @@ asmb(void) a += elfwritephdrs(); a += elfwriteshdrs(); cflush(); - if(a+elfwriteinterp() > ELFRESERVE) + if(a > ELFRESERVE) diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE); break; } @@ -1825,7 +1829,7 @@ genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*)) case SCONST: case SRODATA: case SDATA: - case SELFDATA: + case SELFROSECT: case STYPE: case SSTRING: case SGOSTRING: diff --git a/src/cmd/5l/span.c b/src/cmd/5l/span.c index 338c9665bf..2e1232a1a1 100644 --- a/src/cmd/5l/span.c +++ b/src/cmd/5l/span.c @@ -416,7 +416,7 @@ symaddr(Sym *s) return 0; case STEXT: - case SELFDATA: + case SELFROSECT: case SRODATA: case SDATA: case SBSS: diff --git a/src/cmd/6l/asm.c b/src/cmd/6l/asm.c index 723ac0efe3..fb088fd9ee 100644 --- a/src/cmd/6l/asm.c +++ b/src/cmd/6l/asm.c @@ -559,7 +559,7 @@ doelf(void) /* predefine strings we need for section headers */ shstrtab = lookup(".shstrtab", 0); - shstrtab->type = SELFDATA; + shstrtab->type = SELFROSECT; shstrtab->reachable = 1; elfstr[ElfStrEmpty] = addstring(shstrtab, ""); @@ -591,15 +591,31 @@ doelf(void) elfstr[ElfStrGnuVersion] = addstring(shstrtab, ".gnu.version"); elfstr[ElfStrGnuVersionR] = addstring(shstrtab, ".gnu.version_r"); + /* interpreter string */ + if(interpreter == nil) { + switch(HEADTYPE) { + case Hlinux: + interpreter = linuxdynld; + break; + case Hfreebsd: + interpreter = freebsddynld; + break; + } + } + s = lookup(".interp", 0); + s->type = SELFROSECT; + s->reachable = 1; + addstring(s, interpreter); + /* dynamic symbol table - first entry all zeros */ s = lookup(".dynsym", 0); - s->type = SELFDATA; + s->type = SELFROSECT; s->reachable = 1; s->size += ELF64SYMSIZE; /* dynamic string table */ s = lookup(".dynstr", 0); - s->type = SELFDATA; + s->type = SELFROSECT; s->reachable = 1; if(s->size == 0) addstring(s, ""); @@ -608,44 +624,44 @@ doelf(void) /* relocation table */ s = lookup(".rela", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* global offset table */ s = lookup(".got", 0); s->reachable = 1; - s->type = SDATA; // writable, so not SELFDATA + s->type = SELFSECT; // writable /* hash */ s = lookup(".hash", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".got.plt", 0); s->reachable = 1; - s->type = SDATA; // writable, not SELFDATA + s->type = SELFSECT; // writable s = lookup(".plt", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; elfsetupplt(); s = lookup(".rela.plt", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".gnu.version", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".gnu.version_r", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* define dynamic elf table */ s = lookup(".dynamic", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* * .dynamic table @@ -673,8 +689,11 @@ doelf(void) void shsym(ElfShdr *sh, Sym *s) { - sh->addr = symaddr(s); - sh->off = datoff(sh->addr); + vlong addr; + addr = symaddr(s); + if(sh->flags&SHF_ALLOC) + sh->addr = addr; + sh->off = datoff(addr); sh->size = s->size; } @@ -746,7 +765,7 @@ asmb(void) debug['8'] = 1; /* 64-bit addresses */ /* index of elf text section; needed by asmelfsym, double-checked below */ /* !debug['d'] causes extra sections before the .text section */ - elftextsh = 1; + elftextsh = 2; if(!debug['d']) { elftextsh += 10; if(elfverneed) @@ -890,7 +909,7 @@ asmb(void) break; } } - elfinterp(sh, startva, interpreter); + shsym(sh, lookup(".interp", 0)); ph = newElfPhdr(); ph->type = PT_INTERP; @@ -1014,6 +1033,11 @@ asmb(void) ph->flags = PF_W+PF_R; ph->align = 8; + sh = newElfShstrtab(elfstr[ElfStrShstrtab]); + sh->type = SHT_STRTAB; + sh->addralign = 1; + shsym(sh, lookup(".shstrtab", 0)); + if(elftextsh != eh->shnum) diag("elftextsh = %d, want %d", elftextsh, eh->shnum); for(sect=segtext.sect; sect!=nil; sect=sect->next) @@ -1039,11 +1063,6 @@ asmb(void) dwarfaddelfheaders(); } - sh = newElfShstrtab(elfstr[ElfStrShstrtab]); - sh->type = SHT_STRTAB; - sh->addralign = 1; - shsym(sh, lookup(".shstrtab", 0)); - /* Main header */ eh->ident[EI_MAG0] = '\177'; eh->ident[EI_MAG1] = 'E'; @@ -1069,7 +1088,7 @@ asmb(void) a += elfwritephdrs(); a += elfwriteshdrs(); cflush(); - if(a+elfwriteinterp() > ELFRESERVE) + if(a > ELFRESERVE) diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE); break; case Hwindows: @@ -1111,7 +1130,7 @@ genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*)) case SCONST: case SRODATA: case SDATA: - case SELFDATA: + case SELFROSECT: case SMACHOGOT: case STYPE: case SSTRING: diff --git a/src/cmd/8l/asm.c b/src/cmd/8l/asm.c index 1832b3767b..5d49628588 100644 --- a/src/cmd/8l/asm.c +++ b/src/cmd/8l/asm.c @@ -519,7 +519,7 @@ doelf(void) /* predefine strings we need for section headers */ shstrtab = lookup(".shstrtab", 0); - shstrtab->type = SELFDATA; + shstrtab->type = SELFROSECT; shstrtab->reachable = 1; elfstr[ElfStrEmpty] = addstring(shstrtab, ""); @@ -552,20 +552,31 @@ doelf(void) elfstr[ElfStrGnuVersionR] = addstring(shstrtab, ".gnu.version_r"); /* interpreter string */ + if(interpreter == nil) { + switch(HEADTYPE) { + case Hlinux: + interpreter = linuxdynld; + break; + case Hfreebsd: + interpreter = freebsddynld; + break; + } + } s = lookup(".interp", 0); + s->type = SELFROSECT; s->reachable = 1; - s->type = SELFDATA; + addstring(s, interpreter); /* dynamic symbol table - first entry all zeros */ s = lookup(".dynsym", 0); - s->type = SELFDATA; + s->type = SELFROSECT; s->reachable = 1; s->size += ELF32SYMSIZE; /* dynamic string table */ s = lookup(".dynstr", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; if(s->size == 0) addstring(s, ""); dynstr = s; @@ -573,45 +584,45 @@ doelf(void) /* relocation table */ s = lookup(".rel", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* global offset table */ s = lookup(".got", 0); s->reachable = 1; - s->type = SDATA; // writable, so not SELFDATA + s->type = SELFSECT; // writable /* hash */ s = lookup(".hash", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* got.plt */ s = lookup(".got.plt", 0); s->reachable = 1; - s->type = SDATA; // writable, so not SELFDATA + s->type = SELFSECT; // writable s = lookup(".plt", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".rel.plt", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".gnu.version", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; s = lookup(".gnu.version_r", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; elfsetupplt(); /* define dynamic elf table */ s = lookup(".dynamic", 0); s->reachable = 1; - s->type = SELFDATA; + s->type = SELFROSECT; /* * .dynamic table @@ -638,8 +649,11 @@ doelf(void) void shsym(Elf64_Shdr *sh, Sym *s) { - sh->addr = symaddr(s); - sh->off = datoff(sh->addr); + vlong addr; + addr = symaddr(s); + if(sh->flags&SHF_ALLOC) + sh->addr = addr; + sh->off = datoff(addr); sh->size = s->size; } @@ -696,7 +710,7 @@ asmb(void) if(iself) { /* index of elf text section; needed by asmelfsym, double-checked below */ /* !debug['d'] causes extra sections before the .text section */ - elftextsh = 1; + elftextsh = 2; if(!debug['d']) { elftextsh += 10; if(elfverneed) @@ -950,17 +964,7 @@ asmb(void) sh->type = SHT_PROGBITS; sh->flags = SHF_ALLOC; sh->addralign = 1; - if(interpreter == nil) { - switch(HEADTYPE) { - case Hlinux: - interpreter = linuxdynld; - break; - case Hfreebsd: - interpreter = freebsddynld; - break; - } - } - elfinterp(sh, startva, interpreter); + shsym(sh, lookup(".interp", 0)); ph = newElfPhdr(); ph->type = PT_INTERP; @@ -1084,6 +1088,11 @@ asmb(void) ph->flags = PF_W+PF_R; ph->align = 4; + sh = newElfShstrtab(elfstr[ElfStrShstrtab]); + sh->type = SHT_STRTAB; + sh->addralign = 1; + shsym(sh, lookup(".shstrtab", 0)); + if(elftextsh != eh->shnum) diag("elftextsh = %d, want %d", elftextsh, eh->shnum); for(sect=segtext.sect; sect!=nil; sect=sect->next) @@ -1109,11 +1118,6 @@ asmb(void) dwarfaddelfheaders(); } - sh = newElfShstrtab(elfstr[ElfStrShstrtab]); - sh->type = SHT_STRTAB; - sh->addralign = 1; - shsym(sh, lookup(".shstrtab", 0)); - /* Main header */ eh->ident[EI_MAG0] = '\177'; eh->ident[EI_MAG1] = 'E'; @@ -1144,7 +1148,7 @@ asmb(void) a += elfwritephdrs(); a += elfwriteshdrs(); cflush(); - if(a+elfwriteinterp() > ELFRESERVE) + if(a > ELFRESERVE) diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE); break; @@ -1200,7 +1204,7 @@ genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*)) case SCONST: case SRODATA: case SDATA: - case SELFDATA: + case SELFROSECT: case SMACHO: case SMACHOGOT: case STYPE: diff --git a/src/cmd/ld/data.c b/src/cmd/ld/data.c index 9974dbc513..5cf5f4d7a0 100644 --- a/src/cmd/ld/data.c +++ b/src/cmd/ld/data.c @@ -821,9 +821,8 @@ dodata(void) s = datap; for(; s != nil && s->type < SSYMTAB; s = s->next) { s->type = SRODATA; - t = rnd(s->size, PtrSize); s->value = datsize; - datsize += t; + datsize += rnd(s->size, PtrSize); } sect->len = datsize - sect->vaddr; @@ -836,19 +835,41 @@ dodata(void) datsize += s->size; } sect->len = datsize - sect->vaddr; + datsize = rnd(datsize, PtrSize); /* gopclntab */ sect = addsection(&segtext, ".gopclntab", 04); sect->vaddr = datsize; - for(; s != nil && s->type < SDATA; s = s->next) { + for(; s != nil && s->type < SELFROSECT; s = s->next) { s->type = SRODATA; s->value = datsize; datsize += s->size; } sect->len = datsize - sect->vaddr; + datsize = rnd(datsize, PtrSize); - /* data */ + /* read-only ELF sections */ + for(; s != nil && s->type < SELFSECT; s = s->next) { + sect = addsection(&segtext, s->name, 04); + sect->vaddr = datsize; + s->type = SRODATA; + s->value = datsize; + datsize += rnd(s->size, PtrSize); + sect->len = datsize - sect->vaddr; + } + + /* writable ELF sections */ datsize = 0; + for(; s != nil && s->type < SDATA; s = s->next) { + sect = addsection(&segdata, s->name, 06); + sect->vaddr = datsize; + s->type = SDATA; + s->value = datsize; + datsize += rnd(s->size, PtrSize); + sect->len = datsize - sect->vaddr; + } + + /* data */ sect = addsection(&segdata, ".data", 06); sect->vaddr = 0; for(; s != nil && s->type < SBSS; s = s->next) { @@ -950,38 +971,43 @@ address(void) segtext.fileoff = HEADR; for(s=segtext.sect; s != nil; s=s->next) { s->vaddr = va; - va += s->len; - segtext.len = va - INITTEXT; - va = rnd(va, INITRND); + va += rnd(s->len, PtrSize); } + segtext.len = va - INITTEXT; segtext.filelen = segtext.len; + va = rnd(va, INITRND); + segdata.rwx = 06; segdata.vaddr = va; segdata.fileoff = va - segtext.vaddr + segtext.fileoff; + segdata.filelen = 0; if(HEADTYPE == Hwindows) segdata.fileoff = segtext.fileoff + rnd(segtext.len, PEFILEALIGN); if(HEADTYPE == Hplan9x32) segdata.fileoff = segtext.fileoff + segtext.filelen; + data = nil; for(s=segdata.sect; s != nil; s=s->next) { s->vaddr = va; va += s->len; + segdata.filelen += s->len; segdata.len = va - segdata.vaddr; + if(strcmp(s->name, ".data") == 0) + data = s; } - segdata.filelen = segdata.sect->len; // assume .data is first - + segdata.filelen -= data->next->len; // deduct .bss + text = segtext.sect; rodata = text->next; symtab = rodata->next; pclntab = symtab->next; - data = segdata.sect; for(sym = datap; sym != nil; sym = sym->next) { cursym = sym; if(sym->type < SDATA) sym->value += rodata->vaddr; else - sym->value += data->vaddr; + sym->value += segdata.sect->vaddr; for(sub = sym->sub; sub != nil; sub = sub->sub) sub->value += sym->value; } diff --git a/src/cmd/ld/elf.c b/src/cmd/ld/elf.c index 9c72890d43..3fe8ba83a6 100644 --- a/src/cmd/ld/elf.c +++ b/src/cmd/ld/elf.c @@ -19,7 +19,6 @@ static int elf64; static ElfEhdr hdr; static ElfPhdr *phdr[NSECT]; static ElfShdr *shdr[NSECT]; -static char *interp; typedef struct Elfstring Elfstring; struct Elfstring @@ -304,32 +303,6 @@ elfwritedynentsymsize(Sym *s, int tag, Sym *t) addsize(s, t); } -int -elfwriteinterp(void) -{ - int n; - - if(interp == nil) - return 0; - - n = strlen(interp)+1; - cseek(ELFRESERVE-n); - cwrite(interp, n); - return n; -} - -void -elfinterp(ElfShdr *sh, uint64 startva, char *p) -{ - int n; - - interp = p; - n = strlen(interp)+1; - sh->addr = startva + ELFRESERVE - n; - sh->off = ELFRESERVE - n; - sh->size = n; -} - extern int nelfsym; int elfverneed; @@ -393,7 +366,7 @@ elfdynhash(void) nsym = nelfsym; s = lookup(".hash", 0); - s->type = SELFDATA; + s->type = SELFROSECT; s->reachable = 1; i = nsym; @@ -539,6 +512,12 @@ elfshbits(Section *sect) return nil; found: + for(i=0; iname == off) + return sh; + } + sh = newElfShdr(off); if(sect->vaddr < sect->seg->vaddr + sect->seg->filelen) sh->type = SHT_PROGBITS; diff --git a/src/cmd/ld/lib.h b/src/cmd/ld/lib.h index e2b9858cb0..ee7eb87c00 100644 --- a/src/cmd/ld/lib.h +++ b/src/cmd/ld/lib.h @@ -34,7 +34,6 @@ enum /* order here is order in output file */ STEXT, - SELFDATA, SMACHOPLT, STYPE, SSTRING, @@ -42,6 +41,8 @@ enum SRODATA, SSYMTAB, SPCLNTAB, + SELFROSECT, + SELFSECT, SDATA, SMACHO, /* Mach-O __nl_symbol_ptr */ SMACHOGOT, diff --git a/src/cmd/ld/pe.c b/src/cmd/ld/pe.c index d13801ac02..d235e33c13 100644 --- a/src/cmd/ld/pe.c +++ b/src/cmd/ld/pe.c @@ -396,7 +396,7 @@ dope(void) /* relocation table */ rel = lookup(".rel", 0); rel->reachable = 1; - rel->type = SELFDATA; + rel->type = SELFROSECT; initdynimport(); initdynexport(); diff --git a/src/pkg/debug/elf/file_test.go b/src/pkg/debug/elf/file_test.go index 62e2f3b2df..451d3d5147 100644 --- a/src/pkg/debug/elf/file_test.go +++ b/src/pkg/debug/elf/file_test.go @@ -7,7 +7,10 @@ package elf import ( "debug/dwarf" "encoding/binary" + "net" + "os" "reflect" + "runtime" "testing" ) @@ -210,3 +213,29 @@ func TestDWARFRelocations(t *testing.T) { } } } + +func TestNoSectionOverlaps(t *testing.T) { + // Ensure 6l outputs sections without overlaps. + if runtime.GOOS != "linux" && runtime.GOOS != "freebsd" { + return // not ELF + } + _ = net.ResolveIPAddr // force dynamic linkage + f, err := Open(os.Args[0]) + if err != nil { + t.Error(err) + return + } + for i, si := range f.Sections { + sih := si.SectionHeader + for j, sj := range f.Sections { + sjh := sj.SectionHeader + if i == j || sjh.Type == SHT_NOBITS || sih.Offset == sjh.Offset && sih.Size == 0 { + continue + } + if sih.Offset >= sjh.Offset && sih.Offset < sjh.Offset+sjh.Size { + t.Errorf("ld produced ELF with section %s within %s: 0x%x <= 0x%x..0x%x < 0x%x", + sih.Name, sjh.Name, sjh.Offset, sih.Offset, sih.Offset+sih.Size, sjh.Offset+sjh.Size) + } + } + } +}