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 17 namespace LIBC_NAMESPACE_DECL { 18 19 // Data structure to capture properties of the linux/ELF TLS image. 20 struct 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) 42 using 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. 45 struct AuxEntry { 46 AuxEntryType id; 47 AuxEntryType value; 48 }; 49 50 struct 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. 63 struct 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. 82 struct 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. 100 void init_tls(TLSDescriptor &tls); 101 102 // Cleanup the TLS area as described in |tls_descriptor|. 103 void cleanup_tls(uintptr_t tls_addr, uintptr_t tls_size); 104 105 // Set the thread pointer for the current thread. 106 bool set_thread_ptr(uintptr_t val); 107 108 } // namespace LIBC_NAMESPACE_DECL 109 110 #endif // LLVM_LIBC_CONFIG_LINUX_APP_H 111