[libc] Implement pkey_alloc/free/get/set/mprotect for x86_64 linux (#162362)

This patch provides definitions for `pkey_*` functions for linux x86_64.

`pkey_alloc`, `pkey_free`, and `pkey_mprotect` are simple syscall
wrappers. `pkey_set` and `pkey_get` modify architecture-specific
registers. The logic for these live in architecture specific
directories:

* `libc/src/sys/mman/linux/x86_64/pkey_common.h` has a real
implementation
* `libc/src/sys/mman/linux/generic/pkey_common.h` contains stubs that
just return `ENOSYS`.

Author: jtstogel

libc/config/linux/x86_64/entrypoints.txt

@@ -264,6 +264,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.munlock
     libc.src.sys.mman.munlockall
     libc.src.sys.mman.munmap
+    libc.src.sys.mman.pkey_alloc
+    libc.src.sys.mman.pkey_free
+    libc.src.sys.mman.pkey_get
+    libc.src.sys.mman.pkey_mprotect
+    libc.src.sys.mman.pkey_set
     libc.src.sys.mman.remap_file_pages
     libc.src.sys.mman.posix_madvise
     libc.src.sys.mman.shm_open

libc/include/sys/mman.yaml

@@ -101,6 +101,41 @@ functions:
     arguments:
       - type: void *
       - type: size_t
+  - name: pkey_alloc
+    standards:
+      - Linux
+    return_type: int
+    arguments:
+      - type: unsigned int
+      - type: unsigned int
+  - name: pkey_free
+    standards:
+      - Linux
+    return_type: int
+    arguments:
+      - type: int
+  - name: pkey_get
+    standards:
+      - GNU
+    return_type: int
+    arguments:
+      - type: int
+  - name: pkey_mprotect
+    standards:
+      - Linux
+    return_type: int
+    arguments:
+      - type: void *
+      - type: size_t
+      - type: int
+      - type: int
+  - name: pkey_set
+    standards:
+      - GNU
+    return_type: int
+    arguments:
+      - type: int
+      - type: unsigned int
   - name: posix_madvise
     standards:
       - POSIX

libc/src/sys/mman/CMakeLists.txt

@@ -86,6 +86,41 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.msync
 )
 
+add_entrypoint_object(
+  pkey_alloc
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pkey_alloc
+)
+
+add_entrypoint_object(
+  pkey_free
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pkey_free
+)
+
+add_entrypoint_object(
+  pkey_get
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pkey_get
+)
+
+add_entrypoint_object(
+  pkey_mprotect
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pkey_mprotect
+)
+
+add_entrypoint_object(
+  pkey_set
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.pkey_set
+)
+
 add_entrypoint_object(
   remap_file_pages
   ALIAS

libc/src/sys/mman/linux/CMakeLists.txt

@@ -1,3 +1,10 @@
+add_subdirectory(generic)
+set(ARCH_SUBDIRECTORY generic)
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
+  add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
+  set(ARCH_SUBDIRECTORY ${LIBC_TARGET_ARCHITECTURE})
+endif()
+
 add_entrypoint_object(
   madvise
   SRCS
@@ -50,6 +57,17 @@ add_entrypoint_object(
     libc.src.errno.errno
 )
 
+add_header_library(
+  mprotect_common
+  HDRS
+    mprotect_common.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+    libc.src.__support.error_or
+)
+
 add_entrypoint_object(
   mprotect
   SRCS
@@ -61,6 +79,7 @@ add_entrypoint_object(
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
+    .mprotect_common
 )
 
 add_entrypoint_object(
@@ -166,6 +185,82 @@ add_entrypoint_object(
     libc.src.errno.errno
 )
 
+add_entrypoint_object(
+  pkey_alloc
+  SRCS
+    pkey_alloc.cpp
+  HDRS
+    ../pkey_alloc.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_header_library(
+  pkey_common
+  HDRS
+    pkey_common.h
+  DEPENDS
+    .${ARCH_SUBDIRECTORY}.pkey_common
+)
+
+add_entrypoint_object(
+  pkey_free
+  SRCS
+    pkey_free.cpp
+  HDRS
+    ../pkey_free.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  pkey_get
+  SRCS
+    pkey_get.cpp
+  HDRS
+    ../pkey_get.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+    .pkey_common
+)
+
+add_entrypoint_object(
+  pkey_mprotect
+  SRCS
+    pkey_mprotect.cpp
+  HDRS
+    ../pkey_mprotect.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+    .mprotect_common
+)
+
+add_entrypoint_object(
+  pkey_set
+  SRCS
+    pkey_set.cpp
+  HDRS
+    ../pkey_set.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+    .pkey_common
+)
+
 add_entrypoint_object(
   remap_file_pages
   SRCS

libc/src/sys/mman/linux/generic/CMakeLists.txt

@@ -0,0 +1,9 @@
+add_header_library(
+  pkey_common
+  HDRS
+    pkey_common.h
+  DEPENDS
+    libc.hdr.errno_macros
+    libc.src.__support.common
+    libc.src.__support.error_or
+)

libc/src/sys/mman/linux/generic/pkey_common.h

@@ -0,0 +1,31 @@
+//===---------- Generic stub implementations for pkey functionality. ------===//
+//
+// 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_SYS_MMAN_LINUX_GENERIC_PKEY_COMMON_H_
+#define LLVM_SYS_MMAN_LINUX_GENERIC_PKEY_COMMON_H_
+
+#include "hdr/errno_macros.h" // For ENOSYS
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace pkey_common {
+
+LIBC_INLINE ErrorOr<int> pkey_get([[maybe_unused]] int pkey) {
+  return Error(ENOSYS);
+}
+
+LIBC_INLINE ErrorOr<int> pkey_set([[maybe_unused]] int pkey,
+                                  [[maybe_unused]] unsigned int access_rights) {
+  return Error(ENOSYS);
+}
+
+} // namespace pkey_common
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_SYS_MMAN_LINUX_GENERIC_PKEY_COMMON_H_

libc/src/sys/mman/linux/mprotect.cpp

@@ -11,26 +11,22 @@
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
+#include "src/__support/error_or.h"
 #include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
+#include "src/sys/mman/linux/mprotect_common.h"
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace LIBC_NAMESPACE_DECL {
 
-// This function is currently linux only. It has to be refactored suitably if
-// mprotect is to be supported on non-linux operating systems also.
 LLVM_LIBC_FUNCTION(int, mprotect, (void *addr, size_t size, int prot)) {
-  int ret = LIBC_NAMESPACE::syscall_impl<int>(
-      SYS_mprotect, reinterpret_cast<long>(addr), size, prot);
-
-  // A negative return value indicates an error with the magnitude of the
-  // value being the error code.
-  if (ret < 0) {
-    libc_errno = -ret;
+  ErrorOr<int> result =
+      LIBC_NAMESPACE::mprotect_common::mprotect_impl(addr, size, prot);
+  if (!result.has_value()) {
+    libc_errno = result.error();
     return -1;
   }
-
-  return 0;
+  return result.value();
 }
 
 } // namespace LIBC_NAMESPACE_DECL

libc/src/sys/mman/linux/mprotect_common.h

@@ -0,0 +1,38 @@
+//===---------- Shared Linux implementation of POSIX mprotect. ------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/attributes.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace mprotect_common {
+
+// This function is currently linux only. It has to be refactored suitably if
+// mprotect is to be supported on non-linux operating systems also.
+LIBC_INLINE ErrorOr<int> mprotect_impl(void *addr, size_t size, int prot) {
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_mprotect, reinterpret_cast<long>(addr), size, prot);
+
+  // A negative return value indicates an error with the magnitude of the
+  // value being the error code.
+  if (ret < 0) {
+    return Error(-ret);
+  }
+
+  return 0;
+}
+
+} // namespace mprotect_common
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/mman/linux/pkey_alloc.cpp

@@ -0,0 +1,37 @@
+//===---------- Linux implementation of the Linux pkey_alloc function -----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/mman/pkey_alloc.h"
+
+#include "hdr/errno_macros.h"             // For ENOSYS
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, pkey_alloc,
+                   (unsigned int flags, unsigned int access_rights)) {
+#if !defined(SYS_pkey_alloc)
+  libc_errno = ENOSYS;
+  return -1;
+#else
+  int ret =
+      LIBC_NAMESPACE::syscall_impl<int>(SYS_pkey_alloc, flags, access_rights);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return static_cast<int>(ret);
+#endif
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/mman/linux/pkey_common.h

@@ -0,0 +1,15 @@
+//===---------- Linux implementation of the Linux pkey_mprotect function --===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/macros/properties/architectures.h"
+
+#if defined(LIBC_TARGET_ARCH_IS_X86_64)
+#include "src/sys/mman/linux/x86_64/pkey_common.h"
+#else
+#include "src/sys/mman/linux/generic/pkey_common.h"
+#endif