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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`
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This is a part of #97655.
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declaration" (#98593)
Reverts llvm/llvm-project#98075
bots are broken
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This is a part of #97655.
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Split from #91572
---------
Co-authored-by: Nick Desaulniers (paternity leave) <nickdesaulniers@users.noreply.github.com>
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Avoid `cmpxchg` operation if the function has already been called.
The destination operand of `cmpxchg` may receive a write cycle without
regard to the result of the comparison
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# Motivation
Futex syscalls are widely used in our codebase as synchronization
mechanism. Hence, it may be worthy to abstract out the most common
routines (wait and wake). On the other hand, C++20 also provides
`std::atomic_notify_one/std::atomic_wait/std::atomic_notify_all` which
align with such functionalities. This PR introduces `Futex` as a subtype
of `cpp::Atomic<FutexWordType>` with additional
`notify_one/notify_all/wait` operations.
Providing such wrappers also make future porting easier. For example,
FreeBSD's `_umtx_op` and Darwin's `ulock` can be wrapped in a similar
manner.
### Similar Examples
1. [bionic
futex](https://android.googlesource.com/platform/bionic/+/refs/heads/main/libc/bionic/bionic_futex.cpp)
2. [futex in Rust's
std](https://github.com/rust-lang/rust/blob/8cef37dbb67e9c80702925f19cf298c4203991e4/library/std/src/sys/pal/unix/futex.rs#L21)
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This is step 4 of
https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079
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These were omitted from previous cleanup changes.
Differential Revision: https://reviews.llvm.org/D159066
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This patch is large, but is almost entirely just adding casts to calls
to syscall_impl. Much of the work was done programatically, with human
checking when the syntax or types got confusing.
Reviewed By: mcgrathr
Differential Revision: https://reviews.llvm.org/D156950
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This patch adds a bunch of ifdefs to handle the 32 bit versions of
some syscalls, which often only append a 64 to the name of the syscall
(with exception of SYS_lseek -> SYS_llseek and SYS_futex ->
SYS_futex_time64)
This patch also tries to handle cases where wait4 is not available
(as in riscv32): to implement wait, wait4 and waitpid when wait4 is
not available, we check for alternative wait calls and ultimately rely
on waitid to implement them all.
In riscv32, only waitid is available, so we need it to support this
platform.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D148371
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Add the syscall wrapper function and tests. It's implemented using a
macro to guarantee the minimum number of arguments.
Reviewed By: sivachandra, lntue
Differential Revision: https://reviews.llvm.org/D134919
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The existing thrd_once function has been refactored so that the
implementation can be shared between thrd_once and pthread_once
functions.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D134716
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