From 9ea1be96dbf9678f9fba27221ac267afa1d69ed3 Mon Sep 17 00:00:00 2001
From: belliash <belliash@codingworkshop.eu.org>
Date: Wed, 15 Feb 2023 20:48:48 +0100
Subject: [PATCH] Implement MmZeroPages() routine

---
 xtoskrnl/CMakeLists.txt   |  1 +
 xtoskrnl/mm/amd64/pages.c | 42 +++++++++++++++++++++++++++++++++++++++
 xtoskrnl/mm/i686/pages.c  | 38 +++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 xtoskrnl/mm/amd64/pages.c
 create mode 100644 xtoskrnl/mm/i686/pages.c

diff --git a/xtoskrnl/CMakeLists.txt b/xtoskrnl/CMakeLists.txt
index 4d7efbb..889feae 100644
--- a/xtoskrnl/CMakeLists.txt
+++ b/xtoskrnl/CMakeLists.txt
@@ -21,6 +21,7 @@ list(APPEND XTOSKRNL_SOURCE
     ${XTOSKRNL_SOURCE_DIR}/ke/${ARCH}/krnlinit.c
     ${XTOSKRNL_SOURCE_DIR}/ke/${ARCH}/proc.c
     ${XTOSKRNL_SOURCE_DIR}/mm/kpools.c
+    ${XTOSKRNL_SOURCE_DIR}/mm/${ARCH}/pages.c
     ${XTOSKRNL_SOURCE_DIR}/rtl/atomic.c
     ${XTOSKRNL_SOURCE_DIR}/rtl/byteswap.c
     ${XTOSKRNL_SOURCE_DIR}/rtl/memory.c
diff --git a/xtoskrnl/mm/amd64/pages.c b/xtoskrnl/mm/amd64/pages.c
new file mode 100644
index 0000000..48c1184
--- /dev/null
+++ b/xtoskrnl/mm/amd64/pages.c
@@ -0,0 +1,42 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtoskrnl/mm/amd64/pages.c
+ * DESCRIPTION:     Architecture dependent paging support
+ * DEVELOPERS:      Rafal Kupiec <belliash@codingworkshop.eu.org>
+ */
+
+#include <xtos.h>
+
+
+/**
+ * Fills a section of memory with zeroes like RtlZeroMemory(), but in more efficient way.
+ *
+ * @param Address
+ *        Supplies an address of the page to be filled with zeroes.
+ *
+ * @param Size
+ *        Number of bytes to be filled with zeros. This always should be a multiply of page size.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTFASTCALL
+VOID
+MmZeroPages(IN PVOID Address,
+            IN ULONG Size)
+{
+    asm volatile("xor %%rax, %%rax\n"
+                 "mov %0, %%rdi\n"
+                 "mov %1, %%ecx\n"
+                 "shr $3, %%ecx\n"
+                 "rep stosq\n"
+                 :
+                 : "m" (Address),
+                   "m" (Size)
+                 : "rax",
+                   "rdi",
+                   "ecx",
+                   "memory");
+}
diff --git a/xtoskrnl/mm/i686/pages.c b/xtoskrnl/mm/i686/pages.c
new file mode 100644
index 0000000..073749a
--- /dev/null
+++ b/xtoskrnl/mm/i686/pages.c
@@ -0,0 +1,38 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtoskrnl/mm/i686/pages.c
+ * DESCRIPTION:     Architecture dependent paging support
+ * DEVELOPERS:      Rafal Kupiec <belliash@codingworkshop.eu.org>
+ */
+
+#include <xtos.h>
+
+
+/**
+ * Fills a section of memory with zeroes like RtlZeroMemory(), but in more efficient way.
+ *
+ * @param Address
+ *        Supplies an address of the page to be filled with zeroes.
+ *
+ * @param Size
+ *        Number of bytes to be filled with zeros. This always should be a multiply of page size.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTFASTCALL
+VOID
+MmZeroPages(IN PVOID Address,
+            IN ULONG Size)
+{
+    asm volatile("xor %%eax, %%eax\n"
+                 "rep stosb"
+                 : "=D"(Address),
+                   "=c"(Size)
+                 : "0"(Address),
+                   "1"(Size),
+                   "a"(0)
+                 : "memory");
+}