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//===-- Classes to capture properites of linux applications -----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_CONFIG_LINUX_APP_H
#define LLVM_LIBC_CONFIG_LINUX_APP_H
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/architectures.h"
#include <stdint.h>
namespace LIBC_NAMESPACE_DECL {
// Data structure to capture properties of the linux/ELF TLS image.
struct TLSImage {
// The load address of the TLS.
uintptr_t address;
// The byte size of the TLS image consisting of both initialized and
// uninitialized memory. In ELF executables, it is size of .tdata + size of
// .tbss. Put in another way, it is the memsz field of the PT_TLS header.
uintptr_t size;
// The byte size of initialized memory in the TLS image. In ELF exectubles,
// this is the size of .tdata. Put in another way, it is the filesz of the
// PT_TLS header.
uintptr_t init_size;
// The alignment of the TLS layout. It assumed that the alignment
// value is a power of 2.
uintptr_t align;
};
// Linux manpage on `proc(5)` says that the aux vector is an array of
// unsigned long pairs.
// (see: https://man7.org/linux/man-pages/man5/proc.5.html)
using AuxEntryType = unsigned long;
// Using the naming convention from `proc(5)`.
// TODO: Would be nice to use the aux entry structure from elf.h when available.
struct AuxEntry {
AuxEntryType id;
AuxEntryType value;
};
struct Args {
uintptr_t argc;
// A flexible length array would be more suitable here, but C++ doesn't have
// flexible arrays: P1039 proposes to fix this. So, for now we just fake it.
// Even if argc is zero, "argv[argc] shall be a null pointer"
// (ISO C 5.1.2.2.1) so one is fine. Also, length of 1 is not really wrong as
// |argc| is guaranteed to be atleast 1, and there is an 8-byte null entry at
// the end of the argv array.
uintptr_t argv[1];
};
// Data structure which captures properties of a linux application.
struct AppProperties {
// Page size used for the application.
uintptr_t page_size;
Args *args;
// The properties of an application's TLS image.
TLSImage tls;
// Environment data.
uintptr_t *env_ptr;
// Auxiliary vector data.
AuxEntry *auxv_ptr;
};
[[gnu::weak]] extern AppProperties app;
// The descriptor of a thread's TLS area.
struct TLSDescriptor {
// The size of the TLS area.
uintptr_t size = 0;
// The address of the TLS area. This address can be passed to cleanup
// functions like munmap.
uintptr_t addr = 0;
// The value the thread pointer register should be initialized to.
// Note that, dependending the target architecture ABI, it can be the
// same as |addr| or something else.
uintptr_t tp = 0;
constexpr TLSDescriptor() = default;
};
// Create and initialize the TLS area for the current thread. Should not
// be called before app.tls has been initialized.
void init_tls(TLSDescriptor &tls);
// Cleanup the TLS area as described in |tls_descriptor|.
void cleanup_tls(uintptr_t tls_addr, uintptr_t tls_size);
// Set the thread pointer for the current thread.
bool set_thread_ptr(uintptr_t val);
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_CONFIG_LINUX_APP_H
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