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1//===-- Classes to capture properites of linux applications -----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLVM_LIBC_CONFIG_LINUX_APP_H
10#define LLVM_LIBC_CONFIG_LINUX_APP_H
11
12#include "src/__support/macros/config.h"
13#include "src/__support/macros/properties/architectures.h"
14
15#include <stdint.h>
16
17namespace LIBC_NAMESPACE_DECL {
18
19// Data structure to capture properties of the linux/ELF TLS image.
20struct TLSImage {
21 // The load address of the TLS.
22 uintptr_t address;
23
24 // The byte size of the TLS image consisting of both initialized and
25 // uninitialized memory. In ELF executables, it is size of .tdata + size of
26 // .tbss. Put in another way, it is the memsz field of the PT_TLS header.
27 uintptr_t size;
28
29 // The byte size of initialized memory in the TLS image. In ELF exectubles,
30 // this is the size of .tdata. Put in another way, it is the filesz of the
31 // PT_TLS header.
32 uintptr_t init_size;
33
34 // The alignment of the TLS layout. It assumed that the alignment
35 // value is a power of 2.
36 uintptr_t align;
37};
38
39// Linux manpage on `proc(5)` says that the aux vector is an array of
40// unsigned long pairs.
41// (see: https://man7.org/linux/man-pages/man5/proc.5.html)
42using AuxEntryType = unsigned long;
43// Using the naming convention from `proc(5)`.
44// TODO: Would be nice to use the aux entry structure from elf.h when available.
45struct AuxEntry {
46 AuxEntryType id;
47 AuxEntryType value;
48};
49
50struct Args {
51 uintptr_t argc;
52
53 // A flexible length array would be more suitable here, but C++ doesn't have
54 // flexible arrays: P1039 proposes to fix this. So, for now we just fake it.
55 // Even if argc is zero, "argv[argc] shall be a null pointer"
56 // (ISO C 5.1.2.2.1) so one is fine. Also, length of 1 is not really wrong as
57 // |argc| is guaranteed to be atleast 1, and there is an 8-byte null entry at
58 // the end of the argv array.
59 uintptr_t argv[1];
60};
61
62// Data structure which captures properties of a linux application.
63struct AppProperties {
64 // Page size used for the application.
65 uintptr_t page_size;
66
67 Args *args;
68
69 // The properties of an application's TLS image.
70 TLSImage tls;
71
72 // Environment data.
73 uintptr_t *env_ptr;
74
75 // Auxiliary vector data.
76 AuxEntry *auxv_ptr;
77};
78
79[[gnu::weak]] extern AppProperties app;
80
81// The descriptor of a thread's TLS area.
82struct TLSDescriptor {
83 // The size of the TLS area.
84 uintptr_t size = 0;
85
86 // The address of the TLS area. This address can be passed to cleanup
87 // functions like munmap.
88 uintptr_t addr = 0;
89
90 // The value the thread pointer register should be initialized to.
91 // Note that, dependending the target architecture ABI, it can be the
92 // same as |addr| or something else.
93 uintptr_t tp = 0;
94
95 constexpr TLSDescriptor() = default;
96};
97
98// Create and initialize the TLS area for the current thread. Should not
99// be called before app.tls has been initialized.
100void init_tls(TLSDescriptor &tls);
101
102// Cleanup the TLS area as described in |tls_descriptor|.
103void cleanup_tls(uintptr_t tls_addr, uintptr_t tls_size);
104
105// Set the thread pointer for the current thread.
106bool set_thread_ptr(uintptr_t val);
107
108} // namespace LIBC_NAMESPACE_DECL
109
110#endif // LLVM_LIBC_CONFIG_LINUX_APP_H
111

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source code of libc/config/linux/app.h