From 67be05d3a350a9a4d4db0c07366cad9b93d66610 Mon Sep 17 00:00:00 2001
From: oddcoder <ahmedsoliman@oddcoder.com>
Date: Sun, 3 May 2020 12:33:55 +0200
Subject: [PATCH] Use segments instead of sections for calculating which offset
to write,
I noticed that the implementation is noth precise although it worked.
and instead of using the sections to identify memory addresses of
DT_DEBUG. I used segements
---
src/ld_so/linker.rs | 49 ++++++++++++++++++++++++++-------------------
1 file changed, 28 insertions(+), 21 deletions(-)
diff --git a/src/ld_so/linker.rs b/src/ld_so/linker.rs
index 118122f6..8fc7bc87 100644
--- a/src/ld_so/linker.rs
+++ b/src/ld_so/linker.rs
@@ -689,29 +689,36 @@ impl Linker {
}
}
- // overwrite DT_DEBUG if exist in .dynamic section
- for section in &elf.section_headers {
- // we won't bother with half corrupted elfs.
- let name = elf.shdr_strtab.get(section.sh_name).unwrap().unwrap();
- if name != ".dynamic" {
- continue;
+ // overwrite DT_DEBUG if exist in DYNAMIC segment
+ // first we identify the location of DYNAMIC segment
+ let mut dyn_start = None;
+ let mut debug_start = None;
+ for ph in elf.program_headers.iter() {
+ if ph.p_type == program_header::PT_DYNAMIC {
+ dyn_start = Some(ph.p_vaddr as usize);
}
- let mmap = match self.mmaps.get_mut(*elf_name) {
- Some(some) => some,
- None => continue,
- };
- let dyn_start = section.sh_addr as usize;
- let bytes: [u8; size_of::<Dyn>() / 2] =
- unsafe { transmute((&_r_debug) as *const RTLDDebug as usize) };
- if let Some(dynamic) = elf.dynamic.as_ref() {
- let mut i = 0;
- for entry in &dynamic.dyns {
- if entry.d_tag == DT_DEBUG {
- let start = dyn_start + i * size_of::<Dyn>() + size_of::<Dyn>() / 2;
- mmap[start..start + size_of::<Dyn>() / 2].clone_from_slice(&bytes);
- }
- i += 1;
+ }
+ // next we identify the location of DT_DEBUG in .dynamic section
+ if let Some(dynamic) = elf.dynamic.as_ref() {
+ let mut i = 0;
+ for entry in &dynamic.dyns {
+ if entry.d_tag == DT_DEBUG {
+ debug_start = Some(i as usize);
+ break;
}
+ i += 1;
+ }
+ }
+ if let Some(dyn_start_addr) = dyn_start {
+ if let Some(i) = debug_start {
+ let mmap = match self.mmaps.get_mut(*elf_name) {
+ Some(some) => some,
+ None => continue,
+ };
+ let bytes: [u8; size_of::<Dyn>() / 2] =
+ unsafe { transmute((&_r_debug) as *const RTLDDebug as usize) };
+ let start = dyn_start_addr + i * size_of::<Dyn>() + size_of::<Dyn>() / 2;
+ mmap[start..start + size_of::<Dyn>() / 2].clone_from_slice(&bytes);
}
}
--
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