1//! Linux auxv support, using libc.
2//!
3//! # Safety
4//!
5//! This uses raw pointers to locate and read the kernel-provided auxv array.
6#![allow(unsafe_code)]
7
8use crate::backend::c;
9#[cfg(feature = "param")]
10use crate::ffi::CStr;
11#[cfg(not(feature = "runtime"))]
12use core::ptr::null;
13use linux_raw_sys::elf::*;
14
15// `getauxval` wasn't supported in glibc until 2.16. Also this lets us use
16// `*mut` as the return type to preserve strict provenance.
17#[cfg(not(feature = "runtime"))]
18weak!(fn getauxval(c::c_ulong) -> *mut c::c_void);
19
20// With the "runtime" feature, go ahead and depend on `getauxval` existing so
21// that we never fail.
22#[cfg(feature = "runtime")]
23extern "C" {
24 fn getauxval(type_: c::c_ulong) -> *mut c::c_void;
25}
26
27#[cfg(feature = "runtime")]
28const AT_PHDR: c::c_ulong = 3;
29#[cfg(feature = "runtime")]
30const AT_PHENT: c::c_ulong = 4;
31#[cfg(feature = "runtime")]
32const AT_PHNUM: c::c_ulong = 5;
33#[cfg(feature = "runtime")]
34const AT_ENTRY: c::c_ulong = 9;
35const AT_HWCAP: c::c_ulong = 16;
36#[cfg(feature = "runtime")]
37const AT_RANDOM: c::c_ulong = 25;
38const AT_HWCAP2: c::c_ulong = 26;
39const AT_SECURE: c::c_ulong = 23;
40const AT_EXECFN: c::c_ulong = 31;
41const AT_SYSINFO_EHDR: c::c_ulong = 33;
42
43// Declare `sysconf` ourselves so that we don't depend on all of libc just for
44// this.
45extern "C" {
46 fn sysconf(name: c::c_int) -> c::c_long;
47}
48
49#[cfg(target_os = "android")]
50const _SC_PAGESIZE: c::c_int = 39;
51#[cfg(target_os = "linux")]
52const _SC_PAGESIZE: c::c_int = 30;
53#[cfg(target_os = "android")]
54const _SC_CLK_TCK: c::c_int = 6;
55#[cfg(target_os = "linux")]
56const _SC_CLK_TCK: c::c_int = 2;
57
58#[test]
59fn test_abi() {
60 const_assert_eq!(self::_SC_PAGESIZE, ::libc::_SC_PAGESIZE);
61 const_assert_eq!(self::_SC_CLK_TCK, ::libc::_SC_CLK_TCK);
62 const_assert_eq!(self::AT_HWCAP, ::libc::AT_HWCAP);
63 const_assert_eq!(self::AT_HWCAP2, ::libc::AT_HWCAP2);
64 const_assert_eq!(self::AT_EXECFN, ::libc::AT_EXECFN);
65 const_assert_eq!(self::AT_SECURE, ::libc::AT_SECURE);
66 const_assert_eq!(self::AT_SYSINFO_EHDR, ::libc::AT_SYSINFO_EHDR);
67 #[cfg(feature = "runtime")]
68 const_assert_eq!(self::AT_PHDR, ::libc::AT_PHDR);
69 #[cfg(feature = "runtime")]
70 const_assert_eq!(self::AT_PHNUM, ::libc::AT_PHNUM);
71 #[cfg(feature = "runtime")]
72 const_assert_eq!(self::AT_ENTRY, ::libc::AT_ENTRY);
73 #[cfg(feature = "runtime")]
74 const_assert_eq!(self::AT_RANDOM, ::libc::AT_RANDOM);
75}
76
77#[cfg(feature = "param")]
78#[inline]
79pub(crate) fn page_size() -> usize {
80 unsafe { sysconf(_SC_PAGESIZE) as usize }
81}
82
83#[cfg(feature = "param")]
84#[inline]
85pub(crate) fn clock_ticks_per_second() -> u64 {
86 unsafe { sysconf(_SC_CLK_TCK) as u64 }
87}
88
89#[cfg(feature = "param")]
90#[inline]
91pub(crate) fn linux_hwcap() -> (usize, usize) {
92 #[cfg(not(feature = "runtime"))]
93 unsafe {
94 if let Some(libc_getauxval) = getauxval.get() {
95 let hwcap = libc_getauxval(AT_HWCAP) as usize;
96 let hwcap2 = libc_getauxval(AT_HWCAP2) as usize;
97 (hwcap, hwcap2)
98 } else {
99 (0, 0)
100 }
101 }
102
103 #[cfg(feature = "runtime")]
104 unsafe {
105 let hwcap = getauxval(AT_HWCAP) as usize;
106 let hwcap2 = getauxval(AT_HWCAP2) as usize;
107 (hwcap, hwcap2)
108 }
109}
110
111#[cfg(feature = "param")]
112#[inline]
113pub(crate) fn linux_execfn() -> &'static CStr {
114 #[cfg(not(feature = "runtime"))]
115 unsafe {
116 if let Some(libc_getauxval) = getauxval.get() {
117 CStr::from_ptr(libc_getauxval(AT_EXECFN).cast())
118 } else {
119 cstr!("")
120 }
121 }
122
123 #[cfg(feature = "runtime")]
124 unsafe {
125 CStr::from_ptr(getauxval(AT_EXECFN).cast())
126 }
127}
128
129#[cfg(feature = "runtime")]
130#[inline]
131pub(crate) fn linux_secure() -> bool {
132 unsafe { getauxval(AT_SECURE) as usize != 0 }
133}
134
135#[cfg(feature = "runtime")]
136#[inline]
137pub(crate) fn exe_phdrs() -> (*const c::c_void, usize, usize) {
138 unsafe {
139 let phdr = getauxval(AT_PHDR) as *const c::c_void;
140 let phent = getauxval(AT_PHENT) as usize;
141 let phnum = getauxval(AT_PHNUM) as usize;
142 (phdr, phent, phnum)
143 }
144}
145
146/// `AT_SYSINFO_EHDR` isn't present on all platforms in all configurations, so
147/// if we don't see it, this function returns a null pointer.
148#[inline]
149pub(in super::super) fn sysinfo_ehdr() -> *const Elf_Ehdr {
150 #[cfg(not(feature = "runtime"))]
151 unsafe {
152 if let Some(libc_getauxval: unsafe fn(u64) -> *mut c_void) = getauxval.get() {
153 libc_getauxval(AT_SYSINFO_EHDR) as *const Elf_Ehdr
154 } else {
155 null()
156 }
157 }
158
159 #[cfg(feature = "runtime")]
160 unsafe {
161 getauxval(AT_SYSINFO_EHDR) as *const Elf_Ehdr
162 }
163}
164
165#[cfg(feature = "runtime")]
166#[inline]
167pub(crate) fn entry() -> usize {
168 unsafe { getauxval(AT_ENTRY) as usize }
169}
170
171#[cfg(feature = "runtime")]
172#[inline]
173pub(crate) fn random() -> *const [u8; 16] {
174 unsafe { getauxval(AT_RANDOM) as *const [u8; 16] }
175}
176