From 1182d1200603c9f33ec9968a1a00df5ebd3aa7d8 Mon Sep 17 00:00:00 2001
From: oddcoder <ahmedsoliman@oddcoder.com>
Date: Sun, 3 May 2020 09:48:55 +0200
Subject: [PATCH] Fill gaps in binary memory image
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.
---
src/ld_so/linker.rs | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/src/ld_so/linker.rs b/src/ld_so/linker.rs
index fbd7dd0a..118122f6 100644
--- a/src/ld_so/linker.rs
+++ b/src/ld_so/linker.rs
@@ -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,
--
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