diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 87b78a337b875..4c56d23d96877 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/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
diff --git a/libc/include/sys/mman.yaml b/libc/include/sys/mman.yaml
index 8c207552f9805..91b0f17313a26 100644
--- a/libc/include/sys/mman.yaml
+++ b/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:
+      - GNUExtensions
+    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:
+      - GNUExtensions
+    return_type: int
+    arguments:
+      - type: int
+      - type: unsigned int
   - name: posix_madvise
     standards:
       - POSIX
diff --git a/libc/src/sys/mman/CMakeLists.txt b/libc/src/sys/mman/CMakeLists.txt
index 4d4c2ad376050..c7be1eddacb5e 100644
--- a/libc/src/sys/mman/CMakeLists.txt
+++ b/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
diff --git a/libc/src/sys/mman/linux/CMakeLists.txt b/libc/src/sys/mman/linux/CMakeLists.txt
index 7181bb98a187f..1c79180cbcabb 100644
--- a/libc/src/sys/mman/linux/CMakeLists.txt
+++ b/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
@@ -166,6 +173,74 @@ 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_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
+    .${ARCH_SUBDIRECTORY}.pkey_common
+)
+
+add_entrypoint_object(
+  pkey_mprotect
+  SRCS
+    pkey_mprotect.cpp
+  HDRS
+    ../pkey_mprotect.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.sys.mman.mprotect
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  pkey_set
+  SRCS
+    pkey_set.cpp
+  HDRS
+    ../pkey_set.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+    .${ARCH_SUBDIRECTORY}.pkey_common
+)
+
 add_entrypoint_object(
   remap_file_pages
   SRCS
diff --git a/libc/src/sys/mman/linux/generic/CMakeLists.txt b/libc/src/sys/mman/linux/generic/CMakeLists.txt
new file mode 100644
index 0000000000000..42b6d96c8387e
--- /dev/null
+++ b/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
+)
diff --git a/libc/src/sys/mman/linux/generic/pkey_common.h b/libc/src/sys/mman/linux/generic/pkey_common.h
new file mode 100644
index 0000000000000..51ffe870ce901
--- /dev/null
+++ b/libc/src/sys/mman/linux/generic/pkey_common.h
@@ -0,0 +1,33 @@
+//===---------- 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(int pkey) {
+  (void)pkey;
+  return Error(ENOSYS);
+}
+
+LIBC_INLINE ErrorOr<int> pkey_set(int pkey, unsigned int access_rights) {
+  (void)pkey;
+  (void)access_rights;
+  return Error(ENOSYS);
+}
+
+} // namespace pkey_common
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_SYS_MMAN_LINUX_GENERIC_PKEY_COMMON_H_
diff --git a/libc/src/sys/mman/linux/pkey_alloc.cpp b/libc/src/sys/mman/linux/pkey_alloc.cpp
new file mode 100644
index 0000000000000..baf32013bc5c7
--- /dev/null
+++ b/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 = static_cast<int>(-ret);
+    return -1;
+  }
+  return static_cast<int>(ret);
+#endif
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/linux/pkey_free.cpp b/libc/src/sys/mman/linux/pkey_free.cpp
new file mode 100644
index 0000000000000..0228971bd10f6
--- /dev/null
+++ b/libc/src/sys/mman/linux/pkey_free.cpp
@@ -0,0 +1,35 @@
+//===---------- Linux implementation of the Linux pkey_free 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_free.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_free, (int pkey)) {
+#if !defined(SYS_pkey_free)
+  libc_errno = ENOSYS;
+  return -1;
+#else
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_pkey_free, pkey);
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return 0;
+#endif
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/linux/pkey_get.cpp b/libc/src/sys/mman/linux/pkey_get.cpp
new file mode 100644
index 0000000000000..623b7930c7a23
--- /dev/null
+++ b/libc/src/sys/mman/linux/pkey_get.cpp
@@ -0,0 +1,35 @@
+//===---------- 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/sys/mman/pkey_get.h"
+
+#include "hdr/errno_macros.h" // For ENOSYS
+#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/__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
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, pkey_get, (int pkey)) {
+  ErrorOr<int> ret = LIBC_NAMESPACE::pkey_common::pkey_get(pkey);
+  if (!ret.has_value()) {
+    libc_errno = ret.error();
+    return -1;
+  }
+  return ret.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/linux/pkey_mprotect.cpp b/libc/src/sys/mman/linux/pkey_mprotect.cpp
new file mode 100644
index 0000000000000..15c5d9db39b33
--- /dev/null
+++ b/libc/src/sys/mman/linux/pkey_mprotect.cpp
@@ -0,0 +1,45 @@
+//===---------- 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/sys/mman/pkey_mprotect.h"
+
+#include "hdr/errno_macros.h" // For ENOSYS
+#include "hdr/types/size_t.h"
+#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 "src/sys/mman/mprotect.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, pkey_mprotect,
+                   (void *addr, size_t len, int prot, int pkey)) {
+  // Fall back to mprotect if pkey is -1
+  // to maintain compatibility with kernel versions that don't support pkey.
+  if (pkey == -1) {
+    return LIBC_NAMESPACE::mprotect(addr, len, prot);
+  }
+
+#if !defined(SYS_pkey_mprotect)
+  libc_errno = ENOSYS;
+  return -1;
+#else
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_pkey_mprotect, addr, len,
+                                              prot, pkey);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+#endif
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/linux/pkey_set.cpp b/libc/src/sys/mman/linux/pkey_set.cpp
new file mode 100644
index 0000000000000..7921443f688d3
--- /dev/null
+++ b/libc/src/sys/mman/linux/pkey_set.cpp
@@ -0,0 +1,35 @@
+//===---------- 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/sys/mman/pkey_set.h"
+
+#include "hdr/errno_macros.h" // For ENOSYS
+#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"
+
+#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
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, pkey_set, (int pkey, unsigned int access_rights)) {
+  ErrorOr<int> ret = LIBC_NAMESPACE::pkey_common::pkey_set(pkey, access_rights);
+  if (!ret.has_value()) {
+    libc_errno = ret.error();
+    return -1;
+  }
+  return ret.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/linux/x86_64/CMakeLists.txt b/libc/src/sys/mman/linux/x86_64/CMakeLists.txt
new file mode 100644
index 0000000000000..1ce23af6dbd2a
--- /dev/null
+++ b/libc/src/sys/mman/linux/x86_64/CMakeLists.txt
@@ -0,0 +1,10 @@
+add_header_library(
+  pkey_common
+  HDRS
+    pkey_common.h
+  DEPENDS
+    libc.hdr.errno_macros
+    libc.hdr.stdint_proxy
+    libc.src.__support.common
+    libc.src.__support.error_or
+)
diff --git a/libc/src/sys/mman/linux/x86_64/pkey_common.h b/libc/src/sys/mman/linux/x86_64/pkey_common.h
new file mode 100644
index 0000000000000..17b0e3684c60d
--- /dev/null
+++ b/libc/src/sys/mman/linux/x86_64/pkey_common.h
@@ -0,0 +1,79 @@
+//===---------- x86_64-specific implementations for pkey_{get,set}. -------===//
+//
+// 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_X86_64_PKEY_COMMON_H_
+#define LLVM_SYS_MMAN_LINUX_X86_64_PKEY_COMMON_H_
+
+#include "hdr/errno_macros.h" // For ENOSYS
+#include "hdr/stdint_proxy.h"
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+
+#if !defined(LIBC_TARGET_ARCH_IS_X86_64)
+#error "Invalid include"
+#endif
+
+namespace LIBC_NAMESPACE_DECL {
+namespace pkey_common {
+namespace internal {
+
+constexpr int MAX_KEY = 15;
+constexpr int KEY_MASK = 0x3;
+constexpr int BITS_PER_KEY = 2;
+
+// This will SIGILL on CPUs that don't support PKU / OSPKE,
+// but this case should never be reached as a prior pkey_alloc invocation
+// would have failed more gracefully.
+LIBC_INLINE uint32_t read_prku() {
+  uint32_t pkru = 0;
+  uint32_t edx = 0;
+  asm volatile("rdpkru" : "=a"(pkru), "=d"(edx) : "c"(0));
+  return pkru;
+}
+
+// This will SIGILL on CPUs that don't support PKU / OSPKE,
+// but this case should never be reached as a prior pkey_alloc invocation
+// would have failed more gracefully.
+LIBC_INLINE void write_prku(uint32_t pkru) {
+  asm volatile("wrpkru" : : "a"(pkru), "d"(0), "c"(0));
+}
+
+} // namespace internal
+
+// x86_64 implementation of pkey_get.
+// Returns the access rights for the given pkey on success, errno otherwise.
+LIBC_INLINE ErrorOr<int> pkey_get(int pkey) {
+  if (pkey < 0 || pkey > internal::MAX_KEY) {
+    return Error(EINVAL);
+  }
+
+  uint32_t pkru = internal::read_prku();
+  return (pkru >> (pkey * internal::BITS_PER_KEY)) & internal::KEY_MASK;
+}
+
+// x86_64 implementation of pkey_set.
+// Returns 0 on success, errno otherwise.
+LIBC_INLINE ErrorOr<int> pkey_set(int pkey, unsigned int access_rights) {
+  if (pkey < 0 || pkey > internal::MAX_KEY ||
+      access_rights > internal::KEY_MASK) {
+    return Error(EINVAL);
+  }
+
+  uint32_t pkru = internal::read_prku();
+  pkru &= ~(internal::KEY_MASK << (pkey * internal::BITS_PER_KEY));
+  pkru |=
+      ((access_rights & internal::KEY_MASK) << (pkey * internal::BITS_PER_KEY));
+  internal::write_prku(pkru);
+
+  return 0;
+}
+
+} // namespace pkey_common
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_SYS_MMAN_LINUX_X86_64_PKEY_COMMON_H_
diff --git a/libc/src/sys/mman/pkey_alloc.h b/libc/src/sys/mman/pkey_alloc.h
new file mode 100644
index 0000000000000..c63c6a36c8021
--- /dev/null
+++ b/libc/src/sys/mman/pkey_alloc.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for pkey_alloc function -----------*- C++ -*-===//
+//
+// 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_LIBC_SRC_SYS_MMAN_PKEY_ALLOC_H
+#define LLVM_LIBC_SRC_SYS_MMAN_PKEY_ALLOC_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int pkey_alloc(unsigned int flags, unsigned int access_rights);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_PKEY_ALLOC_H
diff --git a/libc/src/sys/mman/pkey_free.h b/libc/src/sys/mman/pkey_free.h
new file mode 100644
index 0000000000000..a357e9b8c847b
--- /dev/null
+++ b/libc/src/sys/mman/pkey_free.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for pkey_free function ------------*- C++ -*-===//
+//
+// 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_LIBC_SRC_SYS_MMAN_PKEY_FREE_H
+#define LLVM_LIBC_SRC_SYS_MMAN_PKEY_FREE_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int pkey_free(int pkey);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_PKEY_FREE_H
diff --git a/libc/src/sys/mman/pkey_get.h b/libc/src/sys/mman/pkey_get.h
new file mode 100644
index 0000000000000..d41afe08ae371
--- /dev/null
+++ b/libc/src/sys/mman/pkey_get.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for pkey_get function -------------*- C++ -*-===//
+//
+// 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_LIBC_SRC_SYS_MMAN_PKEY_GET_H
+#define LLVM_LIBC_SRC_SYS_MMAN_PKEY_GET_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int pkey_get(int pkey);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_PKEY_GET_H
diff --git a/libc/src/sys/mman/pkey_mprotect.h b/libc/src/sys/mman/pkey_mprotect.h
new file mode 100644
index 0000000000000..c02c61594ecc6
--- /dev/null
+++ b/libc/src/sys/mman/pkey_mprotect.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for pkey_mprotect function --------*- C++ -*-===//
+//
+// 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_LIBC_SRC_SYS_MMAN_PKEY_MPROTECT_H
+#define LLVM_LIBC_SRC_SYS_MMAN_PKEY_MPROTECT_H
+
+#include "hdr/types/size_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int pkey_mprotect(void *addr, size_t len, int prot, int pkey);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_PKEY_MPROTECT_H
diff --git a/libc/src/sys/mman/pkey_set.h b/libc/src/sys/mman/pkey_set.h
new file mode 100644
index 0000000000000..55bafbd11d709
--- /dev/null
+++ b/libc/src/sys/mman/pkey_set.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for pkey_set function -------------*- C++ -*-===//
+//
+// 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_LIBC_SRC_SYS_MMAN_PKEY_SET_H
+#define LLVM_LIBC_SRC_SYS_MMAN_PKEY_SET_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int pkey_set(int pkey, unsigned int access_rights);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_PKEY_SET_H
diff --git a/libc/test/src/sys/mman/linux/CMakeLists.txt b/libc/test/src/sys/mman/linux/CMakeLists.txt
index a362c1cf61cbc..721f89961f7c0 100644
--- a/libc/test/src/sys/mman/linux/CMakeLists.txt
+++ b/libc/test/src/sys/mman/linux/CMakeLists.txt
@@ -67,6 +67,27 @@ add_libc_unittest(
 )
 
 
+add_libc_unittest(
+  pkey_test
+  SUITE
+    libc_sys_mman_unittests
+  SRCS
+    pkey_test.cpp
+  DEPENDS
+    libc.hdr.errno_macros
+    libc.hdr.signal_macros
+    libc.hdr.types.size_t
+    libc.src.sys.mman.mmap
+    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.test.UnitTest.ErrnoCheckingTest
+    libc.test.UnitTest.ErrnoSetterMatcher
+)
+
 add_libc_unittest(
   posix_madvise_test
   SUITE
diff --git a/libc/test/src/sys/mman/linux/pkey_test.cpp b/libc/test/src/sys/mman/linux/pkey_test.cpp
new file mode 100644
index 0000000000000..9c6feae2d457b
--- /dev/null
+++ b/libc/test/src/sys/mman/linux/pkey_test.cpp
@@ -0,0 +1,241 @@
+//===-- Unit tests for pkey functions -------------------------------------===//
+//
+// 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 "hdr/errno_macros.h"
+#include "hdr/signal_macros.h"
+#include "hdr/types/size_t.h"
+#include "src/sys/mman/mmap.h"
+#include "src/sys/mman/munmap.h"
+#include "src/sys/mman/pkey_alloc.h"
+#include "src/sys/mman/pkey_free.h"
+#include "src/sys/mman/pkey_get.h"
+#include "src/sys/mman/pkey_mprotect.h"
+#include "src/sys/mman/pkey_set.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/LibcTest.h"
+#include "test/UnitTest/TestLogger.h"
+
+#include <linux/param.h> // For EXEC_PAGESIZE.
+
+using LIBC_NAMESPACE::testing::tlog;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+using LlvmLibcProtectionKeyTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+constexpr size_t MMAP_SIZE = EXEC_PAGESIZE;
+
+// Wrapper around a pkey to ensure it is freed.
+class PKeyGuard {
+public:
+  int key;
+
+  PKeyGuard() : key(-1) {}
+
+  PKeyGuard(int key) : key(key) {}
+
+  ~PKeyGuard() {
+    if (key != -1) {
+      LIBC_NAMESPACE::pkey_free(key);
+    }
+  }
+};
+
+// Wrapper around mmap to ensure munmap is called.
+class MMapPageGuard {
+public:
+  void *addr = nullptr;
+  size_t size = 0;
+
+  static MMapPageGuard mmap(int prot) {
+    void *addr = LIBC_NAMESPACE::mmap(nullptr, MMAP_SIZE, prot,
+                                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    if (addr == MAP_FAILED) {
+      return MMapPageGuard(nullptr, 0);
+    }
+    return MMapPageGuard(addr, MMAP_SIZE);
+  }
+
+  MMapPageGuard(void *addr, size_t size) : addr(addr), size(size) {}
+
+  ~MMapPageGuard() {
+    if (addr != nullptr) {
+      LIBC_NAMESPACE::munmap(addr, size);
+    }
+  }
+};
+
+bool protection_keys_supported() {
+  static bool supported = []() {
+    PKeyGuard pkey(LIBC_NAMESPACE::pkey_alloc(0, 0));
+    int err = libc_errno;
+    libc_errno = 0;
+
+    if (pkey.key < 0 || (err == ENOSPC || err == ENOSYS || err == EINVAL)) {
+      tlog << "pkey_alloc failed with errno=" << err << "\n";
+      return false;
+    }
+
+    int access_rights = LIBC_NAMESPACE::pkey_get(pkey.key);
+    err = libc_errno;
+    libc_errno = 0;
+    if (access_rights < 0 || err == ENOSYS) {
+      tlog << "pkey_get failed with errno=" << err << "\n";
+      return false;
+    }
+
+    return true;
+  }();
+  return supported;
+}
+
+TEST_F(LlvmLibcProtectionKeyTest, MProtectWithPKeyDisablesWrite) {
+  if (!protection_keys_supported()) {
+    tlog << "Skipping test: pkey is not available\n";
+    return;
+  }
+
+  PKeyGuard pkey(LIBC_NAMESPACE::pkey_alloc(0, PKEY_DISABLE_WRITE));
+  ASSERT_NE(pkey.key, -1);
+
+  MMapPageGuard page = MMapPageGuard::mmap(PROT_READ | PROT_WRITE);
+  ASSERT_NE(page.addr, nullptr);
+
+  volatile char *data = (char *)page.addr;
+  data[0] = 'a';
+
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_mprotect(page.addr, page.size,
+                                            PROT_READ | PROT_WRITE, pkey.key),
+              Succeeds());
+
+  // Read is still allowed.
+  EXPECT_EQ(data[0], 'a');
+
+  // Write is not allowed.
+  EXPECT_DEATH([&data]() { data[0] = 'b'; }, WITH_SIGNAL(SIGSEGV));
+}
+
+TEST_F(LlvmLibcProtectionKeyTest, PKeySetChangesAccessRights) {
+  if (!protection_keys_supported()) {
+    tlog << "Skipping test: pkey is not available\n";
+    return;
+  }
+
+  PKeyGuard pkey(LIBC_NAMESPACE::pkey_alloc(0, 0));
+  ASSERT_NE(pkey.key, -1);
+
+  MMapPageGuard page = MMapPageGuard::mmap(PROT_READ | PROT_WRITE);
+  ASSERT_NE(page.addr, nullptr);
+
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_mprotect(page.addr, page.size,
+                                            PROT_READ | PROT_WRITE, pkey.key),
+              Succeeds());
+
+  // Write is allowed by default.
+  volatile char *data = (char *)page.addr;
+  data[0] = 'a';
+
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_set(pkey.key, PKEY_DISABLE_WRITE),
+              Succeeds());
+
+  // Now read is allowed but write is not.
+  EXPECT_EQ(data[0], 'a');
+  EXPECT_DEATH([&data]() { data[0] = 'b'; }, WITH_SIGNAL(SIGSEGV));
+
+  // Now neither read nor write is allowed.
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_set(pkey.key, PKEY_DISABLE_ACCESS |
+                                                     PKEY_DISABLE_WRITE),
+              Succeeds());
+  EXPECT_DEATH([&data]() { (void)data[0]; }, WITH_SIGNAL(SIGSEGV));
+  EXPECT_DEATH([&data]() { data[0] = 'b'; }, WITH_SIGNAL(SIGSEGV));
+}
+
+TEST_F(LlvmLibcProtectionKeyTest, FallsBackToMProtectForInvalidPKey) {
+  MMapPageGuard page = MMapPageGuard::mmap(PROT_READ | PROT_WRITE);
+  ASSERT_NE(page.addr, nullptr);
+
+  volatile char *data = (char *)page.addr;
+  data[0] = 'a';
+
+  EXPECT_THAT(
+      LIBC_NAMESPACE::pkey_mprotect(page.addr, page.size, PROT_READ, -1),
+      Succeeds());
+
+  // Read is still allowed.
+  EXPECT_EQ(data[0], 'a');
+
+  // Write is not allowed.
+  EXPECT_DEATH([&data]() { data[0] = 'b'; }, WITH_SIGNAL(SIGSEGV));
+}
+
+TEST_F(LlvmLibcProtectionKeyTest, ExhaustedKeysFailsWithENOSPC) {
+  if (!protection_keys_supported()) {
+    tlog << "Skipping test: pkey is not available\n";
+    return;
+  }
+
+  // Use an unreasonably large limit to ensure test is cross-platform.
+  // This limit is intended to be much larger than the actual hardware limit.
+  constexpr int MAX_PKEYS = 64;
+  PKeyGuard pkeys[MAX_PKEYS];
+  for (int i = 0; i < MAX_PKEYS; ++i) {
+    pkeys[i].key = LIBC_NAMESPACE::pkey_alloc(0, 0);
+  }
+
+  // pkey allocation should eventually fail with ENOSPC.
+  PKeyGuard pkey(LIBC_NAMESPACE::pkey_alloc(0, 0));
+  EXPECT_THAT(pkey.key, Fails(ENOSPC));
+  libc_errno = 0;
+}
+
+TEST_F(LlvmLibcProtectionKeyTest, Accessors) {
+  if (!protection_keys_supported()) {
+    tlog << "Skipping test: pkey is not available\n";
+    return;
+  }
+
+  PKeyGuard pkey(LIBC_NAMESPACE::pkey_alloc(0, PKEY_DISABLE_WRITE));
+  ASSERT_NE(pkey.key, -1);
+
+  // Check that pkey_alloc sets the access rights.
+  EXPECT_EQ(LIBC_NAMESPACE::pkey_get(pkey.key), PKEY_DISABLE_WRITE);
+
+  // Check that pkey_set changes the access rights.
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_set(pkey.key, PKEY_DISABLE_ACCESS),
+              Succeeds());
+  EXPECT_EQ(LIBC_NAMESPACE::pkey_get(pkey.key), PKEY_DISABLE_ACCESS);
+}
+
+TEST_F(LlvmLibcProtectionKeyTest, AccessorsErrorForInvalidValues) {
+  if (!protection_keys_supported()) {
+    tlog << "Skipping test: pkey is not available\n";
+    return;
+  }
+
+  PKeyGuard pkey(LIBC_NAMESPACE::pkey_alloc(0, PKEY_DISABLE_WRITE));
+  ASSERT_NE(pkey.key, -1);
+
+  // Pkey is out of bounds in pkey_get.
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_get(100), Fails(EINVAL));
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_get(-1234), Fails(EINVAL));
+
+  // Pkey is out of bounds in pkey_set.
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_set(100, PKEY_DISABLE_ACCESS),
+              Fails(EINVAL));
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_set(-1234, PKEY_DISABLE_ACCESS),
+              Fails(EINVAL));
+
+  // Non-zero flags are not supported in pkey_alloc.
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_alloc(123, PKEY_DISABLE_WRITE),
+              Fails(EINVAL));
+
+  // Access rights are out of bounds.
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_alloc(0, 1000), Fails(EINVAL));
+  EXPECT_THAT(LIBC_NAMESPACE::pkey_set(pkey.key, 1000), Fails(EINVAL));
+}
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index a9675f4b02565..5bd45df678085 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -6899,6 +6899,81 @@ libc_function(
     ],
 )
 
+libc_function(
+    name = "pkey_alloc",
+    srcs = ["src/sys/mman/linux/pkey_alloc.cpp"],
+    hdrs = ["src/sys/mman/pkey_alloc.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
+
+libc_function(
+    name = "pkey_free",
+    srcs = ["src/sys/mman/linux/pkey_free.cpp"],
+    hdrs = ["src/sys/mman/pkey_free.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
+
+libc_function(
+    name = "pkey_get",
+    srcs = ["src/sys/mman/linux/pkey_get.cpp"],
+    hdrs = ["src/sys/mman/pkey_get.h"],
+    deps = [
+        ":__support_common",
+        ":__support_error_or",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":pkey_common",
+    ],
+)
+
+libc_function(
+    name = "pkey_mprotect",
+    srcs = ["src/sys/mman/linux/pkey_mprotect.cpp"],
+    hdrs = ["src/sys/mman/pkey_mprotect.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":mprotect",
+        ":types_size_t",
+    ],
+)
+
+libc_function(
+    name = "pkey_set",
+    srcs = ["src/sys/mman/linux/pkey_set.cpp"],
+    hdrs = ["src/sys/mman/pkey_set.h"],
+    deps = [
+        ":__support_common",
+        ":__support_error_or",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":pkey_common",
+    ],
+)
+
+libc_support_library(
+    name = "pkey_common",
+    hdrs = select({
+        "@platforms//cpu:x86_64": ["src/sys/mman/linux/x86_64/pkey_common.h"],
+        "//conditions:default": ["src/sys/mman/linux/generic/pkey_common.h"],
+    }),
+    deps = [
+        ":__support_common",
+        ":__support_error_or",
+        ":hdr_errno_macros",
+        ":hdr_stdint_proxy",
+    ],
+)
+
 libc_function(
     name = "posix_madvise",
     srcs = ["src/sys/mman/linux/posix_madvise.cpp"],
diff --git a/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel
index b44273123dcad..4a0a81a4b2057 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel
@@ -35,6 +35,7 @@ libc_test_library(
     srcs = [
         "BazelFilePath.cpp",
         "ExecuteFunctionUnix.cpp",
+        "LibcDeathTestExecutors.cpp",
         "LibcTest.cpp",
         "LibcTestMain.cpp",
     ],
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/sys/mman/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/sys/mman/BUILD.bazel
index e2c7f7a8bf60b..13353e2a1722b 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/src/sys/mman/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/src/sys/mman/BUILD.bazel
@@ -92,6 +92,24 @@ libc_test(
     ],
 )
 
+libc_test(
+    name = "pkey_test",
+    srcs = ["linux/pkey_test.cpp"],
+    deps = [
+        "//libc:hdr_errno_macros",
+        "//libc:hdr_signal_macros",
+        "//libc:mmap",
+        "//libc:munmap",
+        "//libc:pkey_alloc",
+        "//libc:pkey_free",
+        "//libc:pkey_get",
+        "//libc:pkey_mprotect",
+        "//libc:pkey_set",
+        "//libc:types_size_t",
+        "//libc/test/UnitTest:test_logger",
+    ],
+)
+
 libc_test(
     name = "posix_madvise_test",
     srcs = ["linux/posix_madvise_test.cpp"],