0db5ba0ce6
Closes https://github.com/llvm/llvm-project/issues/153666 This patch introduces a new centralized AUXV (auxiliary vector) handling mechanism for LLVM libc on Linux, replacing the previous scattered implementation across multiple files. ## Key Changes: ### New Files: - **libc/src/__support/OSUtil/linux/auxv.h**: New header library providing a clean interface for AUXV access with: - `auxv::Entry` struct for AUXV entries (type and value) - `auxv::Vector` class with iterator support for traversing AUXV - `auxv::get()` function for retrieving specific AUXV values - Thread-safe initialization with fallback mechanisms (prctl and /proc/self/auxv) ### Modified Files: 1. **libc/src/__support/OSUtil/linux/CMakeLists.txt**: - Added `auxv` header library declaration with proper dependencies: - libc.hdr.fcntl_macros - libc.src.__support.OSUtil.osutil - libc.src.__support.common - libc.src.__support.CPP.optional - libc.src.__support.threads.callonce 2. **libc/config/linux/app.h**: - Removed `AuxEntry` struct (moved to auxv.h as `auxv::Entry`) - Removed `auxv_ptr` from `AppProperties` struct - Simplified application properties structure 3. **libc/src/sys/auxv/linux/getauxval.cpp**: - Completely refactored to use new auxv.h interface - Removed ~200 lines of complex initialization code - Simplified to just call `auxv::get()` function - Removed dependencies to external symbols (mman, prctl, fcntl, read, close, open) 4. **libc/src/sys/auxv/linux/CMakeLists.txt**: - Updated dependencies to use new auxv header library - Removed dependencies to external symbols (prctl, mman, fcntl, unistd, etc.) 5. **libc/startup/linux/do_start.cpp**: - Updated to use new `auxv::Vector` interface - Changed from pointer-based to iterator-based AUXV traversal - Updated field names (`aux_entry->id` → `aux_entry.type`, `aux_entry->value` → `aux_entry.val`) - Added call to `auxv::Vector::initialize_unsafe()` for early AUXV setup 6. **libc/startup/linux/CMakeLists.txt**: - Added dependency on `libc.src.__support.OSUtil.linux.auxv`
96 lines
3.0 KiB
C++
96 lines
3.0 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 "hdr/stdint_proxy.h"
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#include "src/__support/macros/config.h"
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#include "src/__support/macros/properties/architectures.h"
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namespace LIBC_NAMESPACE_DECL {
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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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struct Args {
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uintptr_t 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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uintptr_t 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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uintptr_t *env_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_DECL
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#endif // LLVM_LIBC_CONFIG_LINUX_APP_H
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