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#![doc = include_str!("../README.md")]
#![no_std]
#![deny(clippy::all)]
#![deny(missing_docs)]
const R_TYPE_MASK: u64 = 0x7fffffff;
use goblin::elf::dynamic::dyn64::Dyn;
use goblin::elf::dynamic::{DT_REL, DT_RELA, DT_RELASZ, DT_RELSZ};
use goblin::elf::reloc::reloc64::Rel;
use goblin::elf::reloc::reloc64::Rela;
use goblin::elf::reloc::R_X86_64_RELATIVE;
#[inline(never)]
pub unsafe extern "C" fn dyn_reloc(dynamic_section: *const u64, base: u64) {
inner_dyn_reloc(dynamic_section, base)
}
#[inline(always)]
unsafe fn inner_dyn_reloc(dynamic_section: *const u64, base: u64) {
let mut dt_rel: Option<u64> = None;
let mut dt_relsz: usize = 0;
let mut dt_rela: Option<u64> = None;
let mut dt_relasz: usize = 0;
let mut dynv = dynamic_section as *const Dyn;
loop {
match (*dynv).d_tag {
0 => break,
DT_REL => dt_rel = Some((*dynv).d_val),
DT_RELSZ => dt_relsz = (*dynv).d_val as usize / core::mem::size_of::<Rel>(),
DT_RELA => dt_rela = Some((*dynv).d_val),
DT_RELASZ => dt_relasz = (*dynv).d_val as usize / core::mem::size_of::<Rela>(),
_ => {}
}
dynv = dynv.add(1);
}
if let Some(dt_rel) = dt_rel {
let rels = core::slice::from_raw_parts((base + dt_rel) as *const Rel, dt_relsz);
rels.iter()
.filter(|rel| rel.r_info & R_TYPE_MASK == R_X86_64_RELATIVE as u64)
.for_each(|rel| {
let rel_addr = (base + rel.r_offset) as *mut u64;
rel_addr.write(rel_addr.read() + base);
});
}
if let Some(dt_rela) = dt_rela {
let relas = core::slice::from_raw_parts((base + dt_rela) as *const Rela, dt_relasz);
relas
.iter()
.filter(|rela| rela.r_info & R_TYPE_MASK == R_X86_64_RELATIVE as u64)
.for_each(|rela| {
let rel_addr_0 = (base + rela.r_offset) as *mut u64;
rel_addr_0.write((base as i64 + rela.r_addend) as u64);
});
}
}
#[inline(never)]
pub unsafe extern "C" fn rcrt(
dynv: *const u64,
sp: *const usize,
pre_main: extern "C" fn() -> !,
) -> ! {
use goblin::elf64::program_header::{ProgramHeader, PT_DYNAMIC};
const AT_PHDR: usize = 3;
const AT_PHENT: usize = 4;
const AT_PHNUM: usize = 5;
let argc: usize = *sp;
let argv = sp.add(1);
let mut i = argc + 1;
while *argv.add(i) != 0 {
i += 1;
}
let auxv_ptr = argv.add(i + 1);
let mut phnum: usize = 0;
let mut phentsize: usize = 0;
let mut ph: usize = 0;
let mut i = 0;
while *auxv_ptr.add(i) != 0 {
match *auxv_ptr.add(i) {
AT_PHDR => ph = *auxv_ptr.add(i + 1),
AT_PHENT => phentsize = *auxv_ptr.add(i + 1),
AT_PHNUM => phnum = *auxv_ptr.add(i + 1),
_ => {}
}
if ph != 0 && phentsize != 0 && phnum != 0 {
break;
}
i += 2;
}
let mut ph = ph as *const ProgramHeader;
let mut i = phnum;
while i != 0 {
if (*ph).p_type == PT_DYNAMIC {
let base = dynv as u64 - (*ph).p_vaddr;
inner_dyn_reloc(dynv, base);
pre_main()
}
ph = (ph as usize + phentsize) as *const ProgramHeader;
i -= 1;
}
unreachable!();
}
#[macro_export]
macro_rules! x86_64_linux_startup {
(fn $name:ident() -> ! $code:block ) => {
#[no_mangle]
#[naked]
pub unsafe extern "sysv64" fn $name() -> ! {
use core::arch::asm;
fn inner() -> ! {
$code
}
asm!(
"lea rdi, [rip + _DYNAMIC]",
"mov rsi, rsp",
"lea rdx, [rip + {INNER}]",
"jmp {RCRT}",
RCRT = sym $crate::rcrt,
INNER = sym inner,
options(noreturn)
)
}
};
}