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cosmopolitan/tool/build/lib/elfwriter.c
Justine Tunney f7780de24b
Make realloc() go 100x faster on Linux/NetBSD 
Cosmopolitan now supports mremap(), which is only supported on Linux and
NetBSD. First, it allows memory mappings to be relocated without copying
them; this can dramatically speed up data structures like std::vector if
the array size grows larger than 256kb. The mremap() system call is also
10x faster than munmap() when shrinking large memory mappings.

There's now two functions, getpagesize() and getgransize() which help to
write portable code that uses mmap(MAP_FIXED). Alternative sysconf() may
be called with our new _SC_GRANSIZE. The madvise() system call now has a
better wrapper with improved documentation.
2024-07-07 12:40:30 -07:00

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "tool/build/lib/elfwriter.h"
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/elf/def.h"
#include "libc/log/check.h"
#include "libc/mem/arraylist2.internal.h"
#include "libc/mem/gc.h"
#include "libc/mem/mem.h"
#include "libc/runtime/memtrack.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/stdalign.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/map.h"
#include "libc/sysv/consts/msync.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/prot.h"
#include "libc/x/xasprintf.h"
static const Elf64_Ehdr kObjHeader = {
.e_ident = {ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3, ELFCLASS64, ELFDATA2LSB, 1,
ELFOSABI_NONE},
.e_type = ET_REL,
.e_machine = EM_NEXGEN32E,
.e_version = 1,
.e_ehsize = sizeof(Elf64_Ehdr),
.e_shentsize = sizeof(Elf64_Shdr),
};
static size_t AppendSection(struct ElfWriter *elf, const char *name,
int sh_type, int sh_flags) {
ssize_t section =
APPEND(&elf->shdrs->p, &elf->shdrs->i, &elf->shdrs->n,
(&(Elf64_Shdr){.sh_type = sh_type,
.sh_flags = sh_flags,
.sh_entsize = elf->entsize,
.sh_addralign = elf->addralign,
.sh_offset = sh_type != SHT_NULL ? elf->wrote : 0,
.sh_name = intern(elf->shstrtab, name)}));
CHECK_NE(-1, section);
return section;
}
static size_t FinishSection(struct ElfWriter *elf) {
size_t section = elf->shdrs->i - 1;
elf->shdrs->p[section].sh_size =
elf->wrote - elf->shdrs->p[section].sh_offset;
return section;
}
static struct ElfWriterSymRef AppendSymbol(struct ElfWriter *elf,
const char *name, int st_info,
int st_other, size_t st_value,
size_t st_size, size_t st_shndx,
enum ElfWriterSymOrder slg) {
ssize_t sym =
APPEND(&elf->syms[slg]->p, &elf->syms[slg]->i, &elf->syms[slg]->n,
(&(Elf64_Sym){.st_info = st_info,
.st_size = st_size,
.st_value = st_value,
.st_other = st_other,
.st_name = intern(elf->strtab, name),
.st_shndx = st_shndx}));
CHECK_NE(-1, sym);
return (struct ElfWriterSymRef){.slg = slg, .sym = sym};
}
static void MakeRelaSection(struct ElfWriter *elf, size_t section) {
size_t shdr, size;
size = (elf->relas->i - elf->relas->j) * sizeof(Elf64_Rela);
elfwriter_align(elf, alignof(Elf64_Rela), sizeof(Elf64_Rela));
shdr = elfwriter_startsection(
elf,
gc(xasprintf("%s%s", ".rela",
&elf->shstrtab->p[elf->shdrs->p[section].sh_name])),
SHT_RELA, SHF_INFO_LINK);
elf->shdrs->p[shdr].sh_info = section;
elfwriter_reserve(elf, size);
elfwriter_commit(elf, size);
FinishSection(elf);
elf->relas->j = elf->relas->i;
}
static void WriteRelaSections(struct ElfWriter *elf, size_t symtab) {
uint32_t sym;
size_t i, j, k;
Elf64_Rela *rela;
for (j = 0, i = 0; i < elf->shdrs->i; ++i) {
if (elf->shdrs->p[i].sh_type == SHT_RELA) {
elf->shdrs->p[i].sh_link = symtab;
for (rela = (Elf64_Rela *)((char *)elf->map + elf->shdrs->p[i].sh_offset);
rela <
(Elf64_Rela *)((char *)elf->map + (elf->shdrs->p[i].sh_offset +
elf->shdrs->p[i].sh_size));
rela++, j++) {
sym = elf->relas->p[j].symkey.sym;
for (k = 0; k < elf->relas->p[j].symkey.slg; ++k) {
sym += elf->syms[k]->i;
}
rela->r_offset = elf->relas->p[j].offset;
rela->r_info = ELF64_R_INFO(sym, elf->relas->p[j].type);
rela->r_addend = elf->relas->p[j].addend;
}
}
}
assert(j == elf->relas->i);
}
static size_t FlushStrtab(struct ElfWriter *elf, const char *name,
struct Interner *strtab) {
size_t size = strtab->i * sizeof(strtab->p[0]);
elfwriter_align(elf, 1, 0);
AppendSection(elf, name, SHT_STRTAB, 0);
mempcpy(elfwriter_reserve(elf, size), strtab->p, size);
elfwriter_commit(elf, size);
return FinishSection(elf);
}
static void FlushTables(struct ElfWriter *elf) {
size_t i, size, symtab;
elfwriter_align(elf, alignof(Elf64_Sym), sizeof(Elf64_Sym));
symtab = AppendSection(elf, ".symtab", SHT_SYMTAB, 0);
for (i = 0; i < ARRAYLEN(elf->syms); ++i) {
size = elf->syms[i]->i * sizeof(Elf64_Sym);
if (size) {
memcpy(elfwriter_reserve(elf, size), elf->syms[i]->p, size);
}
elfwriter_commit(elf, size);
}
FinishSection(elf);
elf->shdrs->p[symtab].sh_link = FlushStrtab(elf, ".strtab", elf->strtab);
elf->ehdr->e_shstrndx = FlushStrtab(elf, ".shstrtab", elf->shstrtab);
WriteRelaSections(elf, symtab);
size = elf->shdrs->i * sizeof(elf->shdrs->p[0]);
elfwriter_align(elf, alignof(Elf64_Shdr), sizeof(elf->shdrs->p[0]));
elf->ehdr->e_shoff = elf->wrote;
elf->ehdr->e_shnum = elf->shdrs->i;
elf->shdrs->p[symtab].sh_info =
elf->syms[kElfWriterSymSection]->i + elf->syms[kElfWriterSymLocal]->i;
mempcpy(elfwriter_reserve(elf, size), elf->shdrs->p, size);
elfwriter_commit(elf, size);
}
struct ElfWriter *elfwriter_open(const char *path, int mode, int arch) {
struct ElfWriter *elf;
CHECK_NOTNULL((elf = calloc(1, sizeof(struct ElfWriter))));
CHECK_NOTNULL((elf->path = strdup(path)));
CHECK_NE(-1, (elf->fd = open(elf->path, O_CREAT | O_TRUNC | O_RDWR, mode)));
CHECK_NE(-1, ftruncate(elf->fd, (elf->mapsize = getgransize())));
CHECK_NE(MAP_FAILED, (elf->map = mmap((void *)(intptr_t)kFixedmapStart,
elf->mapsize, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_FIXED, elf->fd, 0)));
elf->ehdr = memcpy(elf->map, &kObjHeader, (elf->wrote = sizeof(kObjHeader)));
if (!arch) {
#ifdef __x86_64__
arch = EM_NEXGEN32E;
#elif defined(__aarch64__)
arch = EM_AARCH64;
#elif defined(__powerpc64__)
arch = EM_PPC64;
#elif defined(__riscv)
arch = EM_RISCV;
#elif defined(__s390x__)
arch = EM_S390;
#else
#error "unsupported architecture"
#endif
}
elf->ehdr->e_machine = arch;
elf->strtab = newinterner();
elf->shstrtab = newinterner();
intern(elf->strtab, "");
intern(elf->shstrtab, "");
intern(elf->shstrtab, ".shstrtab");
return elf;
}
void elfwriter_close(struct ElfWriter *elf) {
size_t i;
FlushTables(elf);
CHECK_NE(-1, msync(elf->map, elf->wrote, MS_ASYNC));
CHECK_NE(-1, munmap(elf->map, elf->mapsize));
CHECK_NE(-1, ftruncate(elf->fd, elf->wrote));
CHECK_NE(-1, close(elf->fd));
freeinterner(elf->shstrtab);
freeinterner(elf->strtab);
free(elf->shdrs->p);
free(elf->relas->p);
free(elf->path);
for (i = 0; i < ARRAYLEN(elf->syms); ++i) {
free(elf->syms[i]->p);
}
free(elf);
}
void elfwriter_align(struct ElfWriter *elf, size_t addralign, size_t entsize) {
elf->entsize = entsize;
elf->addralign = addralign;
elf->wrote = ROUNDUP(elf->wrote, addralign);
}
size_t elfwriter_startsection(struct ElfWriter *elf, const char *name,
int sh_type, int sh_flags) {
size_t shdr = AppendSection(elf, name, sh_type, sh_flags);
AppendSymbol(elf, "",
sh_type != SHT_NULL ? ELF64_ST_INFO(STB_LOCAL, STT_SECTION)
: ELF64_ST_INFO(STB_LOCAL, STT_NOTYPE),
STV_DEFAULT, 0, 0, shdr, kElfWriterSymSection);
return shdr;
}
void *elfwriter_reserve(struct ElfWriter *elf, size_t size) {
size_t need, greed;
need = elf->wrote + size;
greed = elf->mapsize;
if (need > greed) {
do {
greed = greed + (greed >> 1);
} while (need > greed);
greed = ROUNDUP(greed, getgransize());
CHECK_NE(-1, ftruncate(elf->fd, greed));
CHECK_NE(MAP_FAILED, mmap((char *)elf->map + elf->mapsize,
greed - elf->mapsize, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_FIXED, elf->fd, elf->mapsize));
elf->mapsize = greed;
}
return (char *)elf->map + elf->wrote;
}
void elfwriter_commit(struct ElfWriter *elf, size_t size) {
elf->wrote += size;
}
void elfwriter_finishsection(struct ElfWriter *elf) {
size_t section = FinishSection(elf);
if (elf->relas->j < elf->relas->i)
MakeRelaSection(elf, section);
}
/**
* Appends symbol.
*
* This function should be called between elfwriter_startsection() and
* elfwriter_finishsection(). If that's not possible, then this can be
* called after elfwriter_open() and then elfwriter_setsection() can be
* called later to fix-up the section id.
*/
struct ElfWriterSymRef elfwriter_appendsym(struct ElfWriter *elf,
const char *name, int st_info,
int st_other, size_t st_value,
size_t st_size) {
return AppendSymbol(
elf, name, st_info, st_other, st_value, st_size, elf->shdrs->i - 1,
ELF64_ST_BIND(st_info) == STB_LOCAL ? kElfWriterSymLocal
: kElfWriterSymGlobal);
}
void elfwriter_setsection(struct ElfWriter *elf, struct ElfWriterSymRef sym,
uint16_t st_shndx) {
elf->syms[sym.slg]->p[sym.sym].st_shndx = st_shndx;
}
struct ElfWriterSymRef elfwriter_linksym(struct ElfWriter *elf,
const char *name, int st_info,
int st_other) {
return AppendSymbol(elf, name, st_info, st_other, 0, 0, 0,
kElfWriterSymGlobal);
}
void elfwriter_appendrela(struct ElfWriter *elf, uint64_t r_offset,
struct ElfWriterSymRef symkey, uint32_t type,
int64_t r_addend) {
CHECK_NE(-1, APPEND(&elf->relas->p, &elf->relas->i, &elf->relas->n,
(&(struct ElfWriterRela){.type = type,
.symkey = symkey,
.offset = r_offset,
.addend = r_addend})));
}
uint32_t elfwriter_relatype_abs32(const struct ElfWriter *elf) {
switch (elf->ehdr->e_machine) {
case EM_NEXGEN32E:
return R_X86_64_32;
case EM_AARCH64:
return R_AARCH64_ABS32;
case EM_PPC64:
return R_PPC64_ADDR32;
case EM_RISCV:
return R_RISCV_32;
case EM_S390:
return R_390_32;
default:
notpossible;
}
}
uint32_t elfwriter_relatype_pc32(const struct ElfWriter *elf) {
switch (elf->ehdr->e_machine) {
case EM_NEXGEN32E:
return R_X86_64_PC32;
case EM_AARCH64:
return R_AARCH64_PREL32;
case EM_PPC64:
return R_PPC64_REL32;
case EM_RISCV:
return R_RISCV_RELATIVE;
case EM_S390:
return R_390_PC32;
default:
notpossible;
}
}
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