[libc] add linux mman extension `process_mrelease`

[SchrodingerZhu]

We need to create a process_mrelease wrapper for linux targets, see https://lwn.net/Articles/865341/. This is already inside glibc.

This requires:

• add syscall number into libc/include/sys/syscall.h.def
• implement the entrypoint header similar to libc/src/sys/mman/mmap.h
  • modify libc/src/sys/mman/CMakeLists.txt accordingly
• implement the entrypoint similar to libc/src/sys/mman/linux/mmap.cpp
  • modify libc/src/sys/mman/linux/CMakeLists.txt accordingly
• add the header spec
  • modify functions section in libc/newhdrgen/yaml/sys/mman.yaml
  • modify SysMMan section in libc/spec/linux.td
• add test
  • similar to libc/test/src/sys/mman/linux/mmap_test.cpp
  • modify libc/test/src/sys/mman/linux/CMakeLists.txt accordingly

---

Misc:

• How to build libc for dev: https://libc.llvm.org/full_host_build.html
• Code style and dev guide: https://libc.llvm.org/dev/index.html

If you use vscode, sample settings are as the following (optional settings are useful in speeding up the compilation):

{
    "cmake.sourceDirectory": "${workspaceFolder}/runtimes",
    "cmake.configureSettings": {
        "CMAKE_EXPORT_COMPILE_COMMANDS": true,
        "LLVM_ENABLE_RUNTIMES": [
            "libc",
            "compiler-rt"
        ],
        "LLVM_LIBC_FULL_BUILD": true,
        "LLVM_USE_LINKER": "lld", // optional: requires installing lld
        "CMAKE_CXX_COMPILER_LAUNCHER": "sccache", // optional: requires installing sccache first
        "CMAKE_C_COMPILER_LAUNCHER": "sccache", // optional: requires installing sccache first
        "CMAKE_CXX_COMPILER": "/usr/bin/clang++",
        "CMAKE_C_COMPILER": "/usr/bin/clang",
        "LLVM_LIBC_INCLUDE_SCUDO": true,
        "COMPILER_RT_BUILD_SCUDO_STANDALONE_WITH_LLVM_LIBC": true,
        "COMPILER_RT_BUILD_GWP_ASAN": false,
        "COMPILER_RT_SCUDO_STANDALONE_BUILD_SHARED": false,
        "LIBC_USE_NEW_HEADER_GEN": true
    },
    "cmake.generator": "Ninja", // optional: requires installing Ninja
    "editor.formatOnSave": true,
    "files.insertFinalNewline": true,
    "clangd.arguments": [
        "--header-insertion=never"
    ]
}

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Schrodinger ZHU Yifan (SchrodingerZhu)

We need to create a `process_mrelease` wrapper for linux targets, see https://lwn.net/Articles/865341/. This is already inside glibc.

This requires:

• add syscall number into libc/include/sys/syscall.h.def
• implement the entrypoint header similar to libc/src/sys/mman/mmap.h
  • modify libc/src/sys/mman/CMakeLists.txt accordingly
• implement the entrypoint similar to libc/src/sys/mman/linux/mmap.cpp
  • modify libc/src/sys/mman/linux/CMakeLists.txt accordingly
• add the header spec
  • modify functions section in libc/newhdrgen/yaml/sys/mman.yaml
  • modify SysMMan section in libc/spec/linux.td
• add test
  • similar to libc/test/src/sys/mman/linux/mmap_test.cpp
  • modify libc/test/src/sys/mman/linux/CMakeLists.txt accordingly

---

Misc:

• How to build libc for dev: https://libc.llvm.org/full_host_build.html
• Code style and dev guide: https://libc.llvm.org/dev/index.html

If you use vscode, sample settings are as the following (optional settings are useful in speeding up the compilation):

{
    "cmake.sourceDirectory": "${workspaceFolder}/runtimes",
    "cmake.configureSettings": {
        "CMAKE_EXPORT_COMPILE_COMMANDS": true,
        "LLVM_ENABLE_RUNTIMES": [
            "libc",
            "compiler-rt"
        ],
        "LLVM_LIBC_FULL_BUILD": true,
        "LLVM_USE_LINKER": "lld", // optional: requires installing lld
        "CMAKE_CXX_COMPILER_LAUNCHER": "sccache", // optional: requires installing sccache first
        "CMAKE_C_COMPILER_LAUNCHER": "sccache", // optional: requires installing sccache first
        "CMAKE_CXX_COMPILER": "/usr/bin/clang++",
        "CMAKE_C_COMPILER": "/usr/bin/clang",
        "LLVM_LIBC_INCLUDE_SCUDO": true,
        "COMPILER_RT_BUILD_SCUDO_STANDALONE_WITH_LLVM_LIBC": true,
        "COMPILER_RT_BUILD_GWP_ASAN": false,
        "COMPILER_RT_SCUDO_STANDALONE_BUILD_SHARED": false,
        "LIBC_USE_NEW_HEADER_GEN": true
    },
    "cmake.generator": "Ninja", // optional: requires installing Ninja
    "editor.formatOnSave": true,
    "files.insertFinalNewline": true,
    "clangd.arguments": [
        "--header-insertion=never"
    ]
}

[moar55]

I would like to take this if possible :)

[SchrodingerZhu]

Sure. go ahead.

[vortex73]

I can work on this if its free?

[moar55]

I can work on this if its free?
I am currently working on it ;) Will have a PR up soon

[krishna2803]

Hey @SchrodingerZhu if @moar55 isn't working on this, can I be assigned this? Thanks!

[nickdesaulniers]

Removing the good first issue tag, since it's leading to multiple folks looking to work on it, without any patches. Removing the assignee. At this point, first person to post a PR, I will reassign this issue to (no need to ask to work on this). It may result in duplicated work if there's a mid air collision.