backtrace/symbolize/gimli/
libs_dl_iterate_phdr.rs

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1// Other Unix (e.g. Linux) platforms use ELF as an object file format
2// and typically implement an API called `dl_iterate_phdr` to load
3// native libraries.
4
5use super::mystd::env;
6use super::mystd::ffi::{OsStr, OsString};
7use super::mystd::os::unix::prelude::*;
8use super::{parse_running_mmaps, Library, LibrarySegment};
9use alloc::borrow::ToOwned;
10use alloc::vec::Vec;
11use core::ffi::CStr;
12use core::slice;
13
14struct CallbackData {
15    libs: Vec<Library>,
16    maps: Option<Vec<parse_running_mmaps::MapsEntry>>,
17}
18pub(super) fn native_libraries() -> Vec<Library> {
19    let mut cb_data = CallbackData {
20        libs: Vec::new(),
21        #[cfg(not(target_os = "hurd"))]
22        maps: parse_running_mmaps::parse_maps().ok(),
23        #[cfg(target_os = "hurd")]
24        maps: None,
25    };
26    unsafe {
27        libc::dl_iterate_phdr(Some(callback), core::ptr::addr_of_mut!(cb_data).cast());
28    }
29    cb_data.libs
30}
31
32fn infer_current_exe(
33    maps: &Option<Vec<parse_running_mmaps::MapsEntry>>,
34    base_addr: usize,
35) -> OsString {
36    #[cfg(not(target_os = "hurd"))]
37    if let Some(entries) = maps {
38        let opt_path = entries
39            .iter()
40            .find(|e| e.ip_matches(base_addr) && e.pathname().len() > 0)
41            .map(|e| e.pathname())
42            .cloned();
43        if let Some(path) = opt_path {
44            return path;
45        }
46    }
47
48    env::current_exe().map(|e| e.into()).unwrap_or_default()
49}
50
51/// # Safety
52/// `info` must be a valid pointer.
53/// `data` must be a valid pointer to `CallbackData`.
54#[forbid(unsafe_op_in_unsafe_fn)]
55unsafe extern "C" fn callback(
56    info: *mut libc::dl_phdr_info,
57    _size: libc::size_t,
58    data: *mut libc::c_void,
59) -> libc::c_int {
60    // SAFETY: We are guaranteed these fields:
61    let dlpi_addr = unsafe { (*info).dlpi_addr };
62    let dlpi_name = unsafe { (*info).dlpi_name };
63    let dlpi_phdr = unsafe { (*info).dlpi_phdr };
64    let dlpi_phnum = unsafe { (*info).dlpi_phnum };
65    // SAFETY: We assured this.
66    let CallbackData { libs, maps } = unsafe { &mut *data.cast::<CallbackData>() };
67    // most implementations give us the main program first
68    let is_main = libs.is_empty();
69    // we may be statically linked, which means we are main and mostly one big blob of code
70    let is_static = dlpi_addr == 0;
71    // sometimes we get a null or 0-len CStr, based on libc's whims, but these mean the same thing
72    let no_given_name = dlpi_name.is_null()
73        // SAFETY: we just checked for null
74        || unsafe { *dlpi_name == 0 };
75    let name = if is_static {
76        // don't try to look up our name from /proc/self/maps, it'll get silly
77        env::current_exe().unwrap_or_default().into_os_string()
78    } else if is_main && no_given_name {
79        infer_current_exe(&maps, dlpi_addr as usize)
80    } else {
81        // this fallback works even if we are main, because some platforms give the name anyways
82        if dlpi_name.is_null() {
83            OsString::new()
84        } else {
85            // SAFETY: we just checked for nullness
86            OsStr::from_bytes(unsafe { CStr::from_ptr(dlpi_name) }.to_bytes()).to_owned()
87        }
88    };
89    #[cfg(target_os = "android")]
90    let zip_offset: Option<u64> = {
91        // only check for ZIP-embedded file if we have data from /proc/self/maps
92        maps.as_ref().and_then(|maps| {
93            // check if file is embedded within a ZIP archive by searching for `!/`
94            super::extract_zip_path_android(&name).and_then(|_| {
95                // find MapsEntry matching library's base address and get its file offset
96                maps.iter()
97                    .find(|m| m.ip_matches(dlpi_addr as usize))
98                    .map(|m| m.offset())
99            })
100        })
101    };
102    let headers = if dlpi_phdr.is_null() || dlpi_phnum == 0 {
103        &[]
104    } else {
105        // SAFETY: We just checked for nullness or 0-len slices
106        unsafe { slice::from_raw_parts(dlpi_phdr, dlpi_phnum as usize) }
107    };
108    libs.push(Library {
109        name,
110        #[cfg(target_os = "android")]
111        zip_offset,
112        segments: headers
113            .iter()
114            .map(|header| LibrarySegment {
115                len: header.p_memsz as usize,
116                stated_virtual_memory_address: header.p_vaddr as usize,
117            })
118            .collect(),
119        bias: dlpi_addr as usize,
120    });
121    0
122}
backtrace/symbolize/gimli/libs_dl_iterate_phdr.rs

backtrace/symbolize/gimli/
libs_dl_iterate_phdr.rs
