127 lines
4.1 KiB
C++
127 lines
4.1 KiB
C++
//===-- Classes to capture properites of linux applications -----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_CONFIG_LINUX_APP_H
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#define LLVM_LIBC_CONFIG_LINUX_APP_H
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#include "src/__support/macros/properties/architectures.h"
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#include <stdint.h>
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namespace LIBC_NAMESPACE {
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// Data structure to capture properties of the linux/ELF TLS image.
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struct TLSImage {
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// The load address of the TLS.
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uintptr_t address;
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// The byte size of the TLS image consisting of both initialized and
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// uninitialized memory. In ELF executables, it is size of .tdata + size of
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// .tbss. Put in another way, it is the memsz field of the PT_TLS header.
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uintptr_t size;
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// The byte size of initialized memory in the TLS image. In ELF exectubles,
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// this is the size of .tdata. Put in another way, it is the filesz of the
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// PT_TLS header.
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uintptr_t init_size;
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// The alignment of the TLS layout. It assumed that the alignment
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// value is a power of 2.
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uintptr_t align;
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};
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#if defined(LIBC_TARGET_ARCH_IS_X86_64) || \
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defined(LIBC_TARGET_ARCH_IS_AARCH64) || \
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defined(LIBC_TARGET_ARCH_IS_ANY_RISCV)
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// At the language level, argc is an int. But we use uint64_t as the x86_64
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// ABI specifies it as an 8 byte value. Likewise, in the ARM64 ABI, arguments
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// are usually passed in registers. x0 is a doubleword register, so this is
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// 64 bit for aarch64 as well.
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typedef uintptr_t ArgcType;
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// At the language level, argv is a char** value. However, we use uint64_t as
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// ABIs specify the argv vector be an |argc| long array of 8-byte values.
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typedef uintptr_t ArgVEntryType;
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typedef uintptr_t EnvironType;
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#else
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#error "argc and argv types are not defined for the target platform."
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#endif
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// Linux manpage on `proc(5)` says that the aux vector is an array of
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// unsigned long pairs.
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// (see: https://man7.org/linux/man-pages/man5/proc.5.html)
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using AuxEntryType = unsigned long;
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// Using the naming convention from `proc(5)`.
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// TODO: Would be nice to use the aux entry structure from elf.h when available.
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struct AuxEntry {
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AuxEntryType id;
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AuxEntryType value;
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};
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struct Args {
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ArgcType argc;
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// A flexible length array would be more suitable here, but C++ doesn't have
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// flexible arrays: P1039 proposes to fix this. So, for now we just fake it.
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// Even if argc is zero, "argv[argc] shall be a null pointer"
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// (ISO C 5.1.2.2.1) so one is fine. Also, length of 1 is not really wrong as
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// |argc| is guaranteed to be atleast 1, and there is an 8-byte null entry at
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// the end of the argv array.
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ArgVEntryType argv[1];
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};
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// Data structure which captures properties of a linux application.
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struct AppProperties {
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// Page size used for the application.
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uintptr_t page_size;
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Args *args;
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// The properties of an application's TLS image.
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TLSImage tls;
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// Environment data.
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EnvironType *env_ptr;
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// Auxiliary vector data.
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AuxEntry *auxv_ptr;
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};
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[[gnu::weak]] extern AppProperties app;
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// The descriptor of a thread's TLS area.
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struct TLSDescriptor {
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// The size of the TLS area.
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uintptr_t size = 0;
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// The address of the TLS area. This address can be passed to cleanup
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// functions like munmap.
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uintptr_t addr = 0;
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// The value the thread pointer register should be initialized to.
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// Note that, dependending the target architecture ABI, it can be the
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// same as |addr| or something else.
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uintptr_t tp = 0;
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constexpr TLSDescriptor() = default;
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};
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// Create and initialize the TLS area for the current thread. Should not
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// be called before app.tls has been initialized.
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void init_tls(TLSDescriptor &tls);
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// Cleanup the TLS area as described in |tls_descriptor|.
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void cleanup_tls(uintptr_t tls_addr, uintptr_t tls_size);
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// Set the thread pointer for the current thread.
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bool set_thread_ptr(uintptr_t val);
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} // namespace LIBC_NAMESPACE
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#endif // LLVM_LIBC_CONFIG_LINUX_APP_H
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