[libc] add mremap (#112804)

4 files changed, 87 insertions, 0 deletions

diff --git a/libc/src/sys/mman/CMakeLists.txt b/libc/src/sys/mman/CMakeLists.txt
index 4ea43e14be02..4d4c2ad37605 100644
--- a/libc/src/sys/mman/CMakeLists.txt
+++ b/libc/src/sys/mman/CMakeLists.txt
@@ -106,3 +106,10 @@ add_entrypoint_object(
   DEPENDS
     .${LIBC_TARGET_OS}.shm_unlink
 )
+
+add_entrypoint_object(
+  mremap
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.mremap
+)
diff --git a/libc/src/sys/mman/linux/CMakeLists.txt b/libc/src/sys/mman/linux/CMakeLists.txt
index 47c16f79bc8d..89a0ad1527a0 100644
--- a/libc/src/sys/mman/linux/CMakeLists.txt
+++ b/libc/src/sys/mman/linux/CMakeLists.txt
@@ -25,6 +25,19 @@ add_entrypoint_object(
 )
 
 add_entrypoint_object(
+  mremap
+  SRCS
+    mremap.cpp
+  HDRS
+    ../mremap.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
   munmap
   SRCS
     munmap.cpp
diff --git a/libc/src/sys/mman/linux/mremap.cpp b/libc/src/sys/mman/linux/mremap.cpp
new file mode 100644
index 000000000000..38bcfce833d3
--- /dev/null
+++ b/libc/src/sys/mman/linux/mremap.cpp
@@ -0,0 +1,45 @@
+//===---------- Linux implementation of the POSIX mremap 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/mremap.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "src/__support/macros/config.h"
+#include "src/errno/libc_errno.h"
+#include <linux/param.h> // For EXEC_PAGESIZE.
+#include <stdarg.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(void *, mremap,
+                   (void *old_address, size_t old_size, size_t new_size,
+                    int flags, ... /* void *new_address */)) {
+
+  long ret = 0;
+  void *new_address = nullptr;
+  if (flags & MREMAP_FIXED) {
+    va_list varargs;
+    va_start(varargs, flags);
+    new_address = va_arg(varargs, void *);
+    va_end(varargs);
+  }
+  ret = LIBC_NAMESPACE::syscall_impl<long>(SYS_mremap, old_address, old_size,
+                                           new_size, flags, new_address);
+
+  if (ret < 0 && ret > -EXEC_PAGESIZE) {
+    libc_errno = static_cast<int>(-ret);
+    return MAP_FAILED;
+  }
+
+  return reinterpret_cast<void *>(ret);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/mman/mremap.h b/libc/src/sys/mman/mremap.h
new file mode 100644
index 000000000000..208946bc58a2
--- /dev/null
+++ b/libc/src/sys/mman/mremap.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for mremap 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_MMAN_MREMAP_H
+#define LLVM_LIBC_SRC_SYS_MMAN_MREMAP_H
+
+#include "src/__support/macros/config.h"
+#include <sys/mman.h> // For size_t and off_t
+
+namespace LIBC_NAMESPACE_DECL {
+
+void *mremap(void *old_address, size_t old_size, size_t new_size, int flags,
+             ... /* void *new_address */);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_MREMAP_H