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Fill gaps in binary memory image

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Some ELFs can have gaps between the segments, this results in problems
when mprotecting or when converting (addr + size) into rust slice.
Motivated by this This patch will fill these gaps with mmaped addresses.
In theory no real memory should be allocated because mmap is lazy
allocator.
This commit is contained in:
oddcoder
2020-05-03 09:48:55 +02:00
parent e9615065ac
commit 1182d12006
1 changed files with 31 additions and 1 deletions
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src/ld_so/linker.rs
+31 -1
View File
@@ -383,7 +383,6 @@ impl Linker {
}
// Allocate memory
let mmap = unsafe {
let size = bounds.1 /* - bounds.0 */;
let same_elf = if let Some(prog) = dso.as_ref() {
if prog.name == *elf_name {
true
@@ -395,6 +394,36 @@ impl Linker {
};
if same_elf {
let addr = dso.as_ref().unwrap().base_addr;
let mut size = bounds.1;
// Fill the gaps i the binary
let mut ranges = Vec::new();
for ph in elf.program_headers.iter() {
if ph.p_type == program_header::PT_LOAD {
let voff = ph.p_vaddr as usize % PAGE_SIZE;
let vaddr = ph.p_vaddr as usize - voff;
let vsize = ((ph.p_memsz as usize + voff + PAGE_SIZE - 1) / PAGE_SIZE)
* PAGE_SIZE;
ranges.push((vaddr, vsize));
}
}
ranges.sort();
let mut start = addr;
for (vaddr, vsize) in ranges.iter() {
if start < addr + vaddr {
let gap_size = addr + vaddr - start;
size += gap_size;
sys_mman::mmap(
start as *mut c_void,
addr + vaddr - start,
//TODO: Make it possible to not specify PROT_EXEC on Redox
sys_mman::PROT_READ | sys_mman::PROT_WRITE,
sys_mman::MAP_ANONYMOUS | sys_mman::MAP_PRIVATE,
-1,
0,
);
}
start = addr + vaddr + vsize
}
sys_mman::mprotect(
addr as *mut c_void,
size,
@@ -403,6 +432,7 @@ impl Linker {
_r_debug.insert(addr as usize, &elf_name, addr + l_ld as usize);
slice::from_raw_parts_mut(addr as *mut u8, size)
} else {
let size = bounds.1;
let ptr = sys_mman::mmap(
ptr::null_mut(),
size,