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0e13d1c0b4ad2285108ffe878ba751783ac20eca
zinnia/fs/exec/elf.c
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371 lines
12 KiB
C
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// SPDX-License-Identifier: ISC
#include <zinnia/alloc.h>
#include <zinnia/assert.h>
#include <zinnia/elf.h>
#include <zinnia/errno.h>
#include <zinnia/exec.h>
#include <zinnia/initgraph.h>
#include <zinnia/mman.h>
#include <zinnia/percpu.h>
#include <zinnia/pmap.h>
#include <zinnia/print.h>
#include <zinnia/sched.h>
#include <zinnia/utils.h>
#include <zinnia/vfs.h>
#include <zinnia/vma.h>
#include <zinnia/vmo.h>
#include <bits/elf.h>
#include <stdckdint.h>
#include <uapi/limits.h>
constexpr uintptr_t ELF_DYN_BASE = 0x10000;
struct elf_image {
uintptr_t base;
uintptr_t entry;
uintptr_t phdr;
size_t phnum;
size_t phent;
};
static bool elf_identify(struct vmo* obj) {
elf_ehdr_t ehdr = {};
size_t read;
if (vmo_read(obj, 0, &ehdr, sizeof(ehdr), &read) || read != sizeof(ehdr))
return false;
return memcmp(ehdr.e_ident, ELF_MAG, sizeof(ELF_MAG)) == 0;
}
static errno_t elf_read_interp(struct vmo* obj, const elf_phdr_t* phdr, char** out) {
if (phdr->p_filesz < 2 || phdr->p_filesz > __PATH_MAX)
return ENOEXEC;
char* path = mem_alloc(phdr->p_filesz, ALLOC_NOZERO);
if (!path)
return ENOMEM;
size_t read;
errno_t err = vmo_read(obj, phdr->p_offset, path, phdr->p_filesz, &read);
if (!err && (read != phdr->p_filesz || path[phdr->p_filesz - 1] != '\0'))
err = ENOEXEC;
if (err) {
mem_free(path);
return err;
}
*out = path;
return 0;
}
static errno_t elf_map(
struct vma* space,
struct vmo* obj,
uintptr_t dyn_base,
struct elf_image* out,
char** out_interp
) {
errno_t err;
size_t read;
elf_ehdr_t ehdr = {};
err = vmo_read(obj, 0, &ehdr, sizeof(ehdr), &read);
if (err)
return err;
if (read != sizeof(ehdr))
return ENOEXEC;
// Check if the file is an ELF.
if (memcmp(ehdr.e_ident, ELF_MAG, sizeof(ELF_MAG)) != 0)
return EINVAL;
if (ehdr.e_ident[EI_VERSION] != EV_CURRENT)
return EINVAL;
if (ehdr.e_ident[EI_CLASS] != ELF_ARCH_CLASS)
return EINVAL;
if (ehdr.e_ident[EI_DATA] != ELF_ARCH_DATA)
return EINVAL;
if (ehdr.e_machine != ELF_ARCH_MACHINE)
return EINVAL;
if (ehdr.e_type != ET_EXEC && ehdr.e_type != ET_DYN)
return EINVAL;
const uintptr_t base = ehdr.e_type == ET_DYN ? dyn_base : 0;
uintptr_t entry;
if (ckd_add(&entry, ehdr.e_entry, base) || !arch_mem_addr_is_user(entry))
return ENOEXEC;
const size_t phdrs_size = (size_t)ehdr.e_phnum * ehdr.e_phentsize;
uintptr_t phdrs_end;
if (ehdr.e_phentsize < sizeof(elf_phdr_t) || ehdr.e_phnum == 0 || phdrs_size > 64 * 1024)
return ENOEXEC;
if (ckd_add(&phdrs_end, ehdr.e_phoff, phdrs_size))
return ENOEXEC;
const size_t page_size = arch_mem_page_size();
uintptr_t phdr_addr = 0;
for (size_t i = 0; i < ehdr.e_phnum; i++) {
elf_phdr_t phdr = {};
err = vmo_read(obj, (ehdr.e_phoff + (i * ehdr.e_phentsize)), &phdr, sizeof(phdr), &read);
if (err)
return err;
if (read != sizeof(phdr))
return ENOEXEC;
if (phdr.p_type == PT_PHDR)
phdr_addr = phdr.p_vaddr + base;
if (phdr.p_type == PT_INTERP && out_interp) {
if (*out_interp)
return ENOEXEC;
err = elf_read_interp(obj, &phdr, out_interp);
if (err)
return err;
}
if (phdr.p_type == PT_LOAD) {
if (phdr.p_memsz == 0)
continue;
if (phdr.p_filesz > phdr.p_memsz)
return ENOEXEC;
uintptr_t vaddr, seg_end;
if (ckd_add(&vaddr, phdr.p_vaddr, base) || ckd_add(&seg_end, vaddr, phdr.p_memsz))
return ENOEXEC;
if (!arch_mem_addr_is_user(vaddr) || !arch_mem_addr_is_user(seg_end - 1))
return ENOEXEC;
if (phdr.p_align > 1 && phdr.p_offset % phdr.p_align != phdr.p_vaddr % phdr.p_align)
return ENOEXEC;
if (phdr_addr == 0 && ehdr.e_phoff >= phdr.p_offset && phdrs_end - phdr.p_offset <= phdr.p_filesz)
phdr_addr = vaddr + (ehdr.e_phoff - phdr.p_offset);
enum prot_flags prot = 0;
if (phdr.p_flags & PF_R)
prot |= PROT_READ;
if (phdr.p_flags & PF_W)
prot |= PROT_WRITE;
if (phdr.p_flags & PF_X)
prot |= PROT_EXEC;
const uintptr_t misalign = vaddr & (page_size - 1);
const uintptr_t map_address = vaddr - misalign;
const size_t backed_map_size = (phdr.p_filesz + misalign + page_size - 1) & ~(page_size - 1);
const size_t total_map_size = (phdr.p_memsz + misalign + page_size - 1) & ~(page_size - 1);
if (backed_map_size) {
err = vma_map(space, obj, map_address, backed_map_size, prot, 0, phdr.p_offset - misalign);
if (err)
return err;
}
if (total_map_size > backed_map_size) {
err = vma_map(
space,
nullptr,
map_address + backed_map_size,
total_map_size - backed_map_size,
prot,
0,
0
);
if (err)
return err;
}
const uintptr_t file_end = vaddr + phdr.p_filesz;
if (phdr.p_memsz > phdr.p_filesz && file_end % page_size != 0) {
const uintptr_t zero_end = MIN(ALIGN_UP(file_end, page_size), seg_end);
err = vma_zero(space, file_end, zero_end - file_end);
if (err)
return err;
}
}
}
*out = (struct elf_image){
.base = base,
.entry = entry,
.phdr = phdr_addr,
.phnum = ehdr.e_phnum,
.phent = ehdr.e_phentsize,
};
return 0;
}
static errno_t elf_load(struct process* proc, struct exec_info* info, uintptr_t* out_ip, uintptr_t* out_sp) {
struct elf_image exe = {};
char* interp_path = nullptr;
errno_t err = elf_map(info->space, info->file_obj, ELF_DYN_BASE, &exe, &interp_path);
uintptr_t entry = exe.entry;
uintptr_t interp_base = 0;
if (!err && interp_path) {
struct vmo* interp;
err = exec_open(proc, interp_path, &interp);
if (!err) {
struct elf_image ld;
if (!elf_identify(interp))
err = ELIBBAD;
else
err = elf_map(info->space, interp, (uintptr_t)1 << (mem_high_shift() - 2), &ld, nullptr);
if (!err) {
entry = ld.entry;
interp_base = ld.base;
}
vmo_unref(interp);
}
}
mem_free(interp_path);
if (err)
return err;
const size_t page_size = arch_mem_page_size();
const uintptr_t highest = ((uintptr_t)1 << (mem_high_shift() - 1)) - page_size;
const size_t stack_size = 2 * 1024 * 1024; // 2MiB
const uintptr_t stack_start = highest - stack_size;
err = vma_map(info->space, nullptr, stack_start, stack_size, PROT_READ | PROT_WRITE, 0, 0);
if (err)
return err;
// Fill in stack info.
uintptr_t stack_off = stack_size;
uintptr_t execfn = 0;
if (info->exec_path) {
const char nul = 0;
stack_off -= 1;
vma_write(info->space, stack_start + stack_off, &nul, sizeof(nul));
const size_t len = strlen(info->exec_path);
stack_off -= len;
vma_write(info->space, stack_start + stack_off, info->exec_path, len);
execfn = stack_start + stack_off;
}
// TODO: Instead of allocating, calculate it on the fly.
size_t num_envp = 0;
for (const char** ptr = info->envp; *ptr != nullptr; ptr++) {
num_envp++;
}
size_t num_argv = 0;
for (const char** ptr = info->argv; *ptr != nullptr; ptr++) {
num_argv++;
}
size_t strings_size = 0;
for (size_t env = 0; env < num_envp; env++)
strings_size += strlen(info->envp[env]) + 1;
for (size_t arg = 0; arg < num_argv; arg++)
strings_size += strlen(info->argv[arg]) + 1;
uintptr_t* envp_offsets = mem_alloc(num_envp * sizeof(uintptr_t), 0);
uintptr_t* argv_offsets = mem_alloc(num_argv * sizeof(uintptr_t), 0);
if ((num_envp && !envp_offsets) || (num_argv && !argv_offsets)) {
mem_free(envp_offsets);
mem_free(argv_offsets);
return ENOMEM;
}
for (size_t env = 0; env < num_envp; env++) {
const char nul = 0;
stack_off -= 1;
vma_write(info->space, stack_start + stack_off, &nul, sizeof(nul));
const size_t len = strlen(info->envp[env]);
stack_off -= len;
vma_write(info->space, stack_start + stack_off, info->envp[env], len);
envp_offsets[env] = stack_start + stack_off;
}
for (size_t arg = 0; arg < num_argv; arg++) {
const char nul = 0;
stack_off -= 1;
vma_write(info->space, stack_start + stack_off, &nul, sizeof(nul));
const size_t len = strlen(info->argv[arg]);
stack_off -= len;
vma_write(info->space, stack_start + stack_off, info->argv[arg], len);
argv_offsets[arg] = stack_start + stack_off;
}
stack_off = ALIGN_DOWN(stack_off, 16);
// Align the stack if argc + argv + envp does not add up to 16 byte alignment.
if ((1 + num_argv + num_envp) & 1) {
stack_off -= sizeof(uintptr_t);
uintptr_t zero = 0;
vma_write(info->space, stack_start + stack_off, &zero, sizeof(zero));
}
#define WRITE_AUXV(auxv, value) \
do { \
stack_off -= sizeof(uintptr_t); \
uintptr_t auxv_val = value; \
vma_write(info->space, stack_start + stack_off, &auxv_val, sizeof(uintptr_t)); \
stack_off -= sizeof(uintptr_t); \
auxv_val = auxv; \
vma_write(info->space, stack_start + stack_off, &auxv_val, sizeof(uintptr_t)); \
} while (0)
// Write auxiliary values.
WRITE_AUXV(AT_NULL, 0);
WRITE_AUXV(AT_SECURE, 0);
WRITE_AUXV(AT_PAGESZ, page_size);
WRITE_AUXV(AT_PHNUM, exe.phnum);
WRITE_AUXV(AT_PHENT, exe.phent);
WRITE_AUXV(AT_ENTRY, exe.entry);
if (exe.phdr)
WRITE_AUXV(AT_PHDR, exe.phdr);
if (interp_base)
WRITE_AUXV(AT_BASE, interp_base);
if (execfn)
WRITE_AUXV(AT_EXECFN, execfn);
// envp pointers.
stack_off -= sizeof(uintptr_t);
const uintptr_t zero = 0;
vma_write(info->space, stack_start + stack_off, &zero, sizeof(zero));
for (size_t env = num_envp; env > 0; env--) {
stack_off -= sizeof(uintptr_t);
vma_write(info->space, stack_start + stack_off, &envp_offsets[env - 1], sizeof(envp_offsets[env - 1]));
}
// argv pointers.
stack_off -= sizeof(uintptr_t);
vma_write(info->space, stack_start + stack_off, &zero, sizeof(zero));
for (size_t arg = num_argv; arg > 0; arg--) {
stack_off -= sizeof(uintptr_t);
vma_write(info->space, stack_start + stack_off, &argv_offsets[arg - 1], sizeof(argv_offsets[arg - 1]));
}
mem_free(envp_offsets);
mem_free(argv_offsets);
// argc
stack_off -= sizeof(uintptr_t);
uintptr_t argc = num_argv;
vma_write(info->space, stack_start + stack_off, &argc, sizeof(argc));
*out_ip = entry;
*out_sp = highest - stack_size + stack_off;
return 0;
}
static struct exec_format elf_format = {
.name = "elf",
.identify = elf_identify,
.load = elf_load,
};
static void elf_stage_init(struct boot_info*) {
exec_register(&elf_format);
}
INIT_TASK(elf_stage, "fs.exec.elf", elf_stage_init);
INIT_DEPENDS(elf_stage, mem_stage);
INIT_ENTAILS(elf_stage, vfs_stage);
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