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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,134 @@ | ||
| use libc::c_void; | ||
| use plt_rs::{collect_modules, DynamicLibrary, RelocationTable}; | ||
|
|
||
| /// Make sure we can load all the modules we load ourselves | ||
| /// A simple sanity check, we are not checking the modules contents in any meaningful way. | ||
| /// But this works great to catch issues, because realistically we should never run into a issue parsing libraries. | ||
| #[test] | ||
| fn can_load_own_link_map() {} | ||
| fn can_load_own_link_map() { | ||
| let entries = collect_modules(); | ||
|
|
||
| for entry in entries.into_iter() { | ||
| if let Ok(dynamic_lib) = DynamicLibrary::initialize(entry) { | ||
| let dynamic_symbols = dynamic_lib.symbols().expect("symbols..."); | ||
| let string_table = dynamic_lib.string_table(); | ||
| if let Some(dyn_relas) = dynamic_lib.addend_relocs() { | ||
| dyn_relas | ||
| .entries() | ||
| .iter() | ||
| .flat_map(|e| { | ||
| dynamic_symbols.resolve_name(e.symbol_index() as usize, string_table) | ||
| }) | ||
| .filter(|s| !s.is_empty()) | ||
| .for_each(|s| println!("\t{}", s)); | ||
| } | ||
|
|
||
| if let Some(dyn_relocs) = dynamic_lib.relocs() { | ||
| dyn_relocs | ||
| .entries() | ||
| .iter() | ||
| .flat_map(|e| { | ||
| dynamic_symbols.resolve_name(e.symbol_index() as usize, string_table) | ||
| }) | ||
| .filter(|s| !s.is_empty()) | ||
| .for_each(|s| println!("\t{}", s)); | ||
| } | ||
|
|
||
| if let Some(plt) = dynamic_lib.plt() { | ||
| match plt { | ||
| RelocationTable::WithAddend(rel) => { | ||
| rel.entries() | ||
| .iter() | ||
| .flat_map(|e| { | ||
| dynamic_symbols | ||
| .resolve_name(e.symbol_index() as usize, string_table) | ||
| }) | ||
| .filter(|s| !s.is_empty()) | ||
| .for_each(|s| println!("\t{}", s)); | ||
| } | ||
| RelocationTable::WithoutAddend(rel) => { | ||
| rel.entries() | ||
| .iter() | ||
| .flat_map(|e| { | ||
| dynamic_symbols | ||
| .resolve_name(e.symbol_index() as usize, string_table) | ||
| }) | ||
| .filter(|s| !s.is_empty()) | ||
| .for_each(|s| println!("\t{}", s)); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| unsafe fn getpid() -> u32 { | ||
| 999 | ||
| } | ||
|
|
||
| /// Finding executable target differs on unix and android | ||
| #[cfg(target_os = "linux")] | ||
| fn find_executable<'a>() -> Option<plt_rs::LoadedLibrary<'a>> { | ||
| let loaded_modules = collect_modules(); | ||
| loaded_modules.into_iter().next() | ||
| } | ||
|
|
||
| /// Finding executable target differs on unix and android | ||
| #[cfg(target_os = "android")] | ||
| fn find_executable<'a>() -> Option<plt_rs::LoadedLibrary<'a>> { | ||
| let executable = std::env::current_exe().expect("current exe"); | ||
| let file_stem = executable.file_stem()?; | ||
| let file_stem = file_stem.to_str()?; | ||
| let loaded_modules = collect_modules(); | ||
| loaded_modules | ||
| .into_iter() | ||
| .filter(|lib| lib.name().contains(file_stem)) | ||
| .next() | ||
| } | ||
| #[test] | ||
| fn can_hook_getpid() {} | ||
| fn can_hook_getpid() { | ||
| let my_pid = unsafe { libc::getpid() }; | ||
| println!("application pid is {my_pid}"); | ||
|
|
||
| let executable_entry = find_executable().expect("can find executable"); | ||
| println!("successfully identified executable"); | ||
|
|
||
| let dyn_lib = DynamicLibrary::initialize(executable_entry).expect("can load"); | ||
| println!("successfully initialied dynamic library for instrumentation"); | ||
|
|
||
| let target_function = dyn_lib | ||
| .try_find_function("getpid") | ||
| .expect("executable should link getpid"); | ||
| println!( | ||
| "successfully identified libc getpid offset: {:#X?}", | ||
| target_function.r_offset | ||
| ); | ||
|
|
||
| let base_addr = dyn_lib.library().addr(); | ||
| let plt_fn_ptr = (base_addr + target_function.r_offset as usize) as *mut *mut libc::c_void; | ||
| let page_size = unsafe { libc::sysconf(libc::_SC_PAGE_SIZE) as usize }; | ||
| let plt_page = ((plt_fn_ptr as usize / page_size) * page_size) as *mut libc::c_void; | ||
| println!("page start for function is {plt_page:#X?}"); | ||
|
|
||
| let _stored_address = unsafe { | ||
| // Set the memory page to read, write | ||
| let prot_res = libc::mprotect(plt_page, page_size, libc::PROT_WRITE | libc::PROT_READ); | ||
| if prot_res != 0 { | ||
| panic!("failed to set prot res"); | ||
| } | ||
|
|
||
| // Replace the function address | ||
| let previous_address = std::ptr::replace(plt_fn_ptr, getpid as *mut _); | ||
|
|
||
| // Set the memory page protection back to read only | ||
| let prot_res = libc::mprotect(plt_page, page_size, libc::PROT_READ); | ||
| if prot_res != 0 { | ||
| panic!("failed to set prot res"); | ||
| } | ||
|
|
||
| previous_address as *const c_void | ||
| }; | ||
|
|
||
| let get_pid = unsafe { libc::getpid() }; | ||
| assert_eq!(get_pid, 999) | ||
| } |