From 53e9b9758e470950141b609526c22d6de405e9b1 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 23 Nov 2021 11:47:32 +0100
Subject: [PATCH] LibCore: Add syscall wrapper for mmap()

For convenience on SerenityOS, this also takes a custom alignment
request, and a memory region name. These are non-POSIX extensions.
---
 Userland/Libraries/LibCore/System.cpp | 19 +++++++++++++++++++
 Userland/Libraries/LibCore/System.h   |  1 +
 2 files changed, 20 insertions(+)

diff --git a/Userland/Libraries/LibCore/System.cpp b/Userland/Libraries/LibCore/System.cpp
index 611817c135..6f44dffe83 100644
--- a/Userland/Libraries/LibCore/System.cpp
+++ b/Userland/Libraries/LibCore/System.cpp
@@ -8,6 +8,7 @@
 #include <LibSystem/syscall.h>
 #include <fcntl.h>
 #include <stdarg.h>
+#include <sys/mman.h>
 
 #define HANDLE_SYSCALL_RETURN_VALUE(syscall_name, rc, success_value) \
     if ((rc) < 0) {                                                  \
@@ -66,4 +67,22 @@ ErrorOr<int> fcntl(int fd, int command, ...)
     return rc;
 }
 
+ErrorOr<void*> mmap(void* address, size_t size, int protection, int flags, int fd, off_t offset, [[maybe_unused]] size_t alignment, [[maybe_unused]] StringView name)
+{
+#ifdef __serenity__
+    Syscall::SC_mmap_params params { (uintptr_t)address, size, alignment, protection, flags, fd, offset, { name.characters_without_null_termination(), name.length() } };
+    ptrdiff_t rc = syscall(SC_mmap, &params);
+    if (rc < 0 && rc > -EMAXERRNO)
+        return Error::from_syscall("mmap"sv, rc);
+    return reinterpret_cast<void*>(rc);
+#else
+    // NOTE: Regular POSIX mmap() doesn't support custom alignment requests.
+    VERIFY(!alignment);
+    auto* ptr = ::mmap(address, size, protection, flags, fd, offset);
+    if (ptr == MAP_FAILED)
+        return Error::from_syscall("mmap"sv, -errno);
+    return ptr;
+#endif
+}
+
 }
diff --git a/Userland/Libraries/LibCore/System.h b/Userland/Libraries/LibCore/System.h
index 9af82b2233..933c3bb71e 100644
--- a/Userland/Libraries/LibCore/System.h
+++ b/Userland/Libraries/LibCore/System.h
@@ -20,5 +20,6 @@ ErrorOr<void> unveil(StringView path, StringView permissions);
 ErrorOr<void> sigaction(int signal, struct sigaction const* action, struct sigaction* old_action);
 ErrorOr<struct stat> fstat(int fd);
 ErrorOr<int> fcntl(int fd, int command, ...);
+ErrorOr<void*> mmap(void* address, size_t, int protection, int flags, int fd, off_t, size_t alignment = 0, StringView name = {});
 
 }