From a9555bb5b541ebc64839065ed0a9cae6774e52c1 Mon Sep 17 00:00:00 2001
From: plutoo <plutoo@universe>
Date: Sun, 8 Oct 2017 15:11:59 +0200
Subject: [PATCH] Implement virtual memory allocator

---
 nx/include/switch/result.h |   2 +
 nx/source/kernel/virtmem.c | 122 ++++++++++++++++++++++++++++++++++---
 2 files changed, 117 insertions(+), 7 deletions(-)

diff --git a/nx/include/switch/result.h b/nx/include/switch/result.h
index ea7b475f..daaaedf6 100644
--- a/nx/include/switch/result.h
+++ b/nx/include/switch/result.h
@@ -22,3 +22,5 @@
 #define LIBNX_BADRELOC       1
 #define LIBNX_OUTOFMEM       2
 #define LIBNX_ALREADYMAPPED  3
+#define LIBNX_BADGETINFO     4
+#define LIBNX_BADQUERYMEMORY 5
diff --git a/nx/source/kernel/virtmem.c b/nx/source/kernel/virtmem.c
index 426eef03..4bcc0138 100644
--- a/nx/source/kernel/virtmem.c
+++ b/nx/source/kernel/virtmem.c
@@ -1,21 +1,129 @@
 #include <switch.h>
 
-static u8* g_VirtBase;
+typedef struct {
+    u64  start;
+    u64  end;
+} VirtualRegion;
+
+enum {
+    REGION_MAP =0,
+    REGION_HEAP=1,
+    REGION_UNK =2,
+    REGION_MAX
+};
+
+static VirtualRegion g_AddressSpace;
+static VirtualRegion g_Region[REGION_MAX];
+static u64 g_CurrentAddr;
+
+static Result _GetRegionFromInfo(VirtualRegion* r, u64 id0_addr, u32 id0_sz) {
+    u64 base;
+    Result rc = svcGetInfo(&base, id0_addr, CUR_PROCESS_HANDLE, 0);
+
+    if (R_SUCCEEDED(rc)) {
+        u64 size;
+        rc = svcGetInfo(&size, id0_sz, CUR_PROCESS_HANDLE, 0);
+
+        if (R_SUCCEEDED(rc)) {
+            r->start = base;
+            r->end   = base + size;
+        }
+    }
+
+    return rc;
+}
+
+static inline bool _InRegion(VirtualRegion* r, u64 addr) {
+    return (addr >= r->start) && (addr < (r->end-1));
+}
 
 void virtmemSetup() {
-    // TODO: Implement this.
+    if (R_FAILED(_GetRegionFromInfo(&g_AddressSpace, 12, 13))) {
+        // Default values in case we're running on 1.0.0
+        // Assumes 36-bit address space
+        g_AddressSpace.start =    0x8000000ull;
+        g_AddressSpace.end   = 0x1000000000ull;
+    }
+
+    if (R_FAILED(_GetRegionFromInfo(&g_Region[REGION_MAP], 2, 3))) {
+        fatalSimple(MAKERESULT(MODULE_LIBNX, LIBNX_BADGETINFO));
+    }
+
+    if (R_FAILED(_GetRegionFromInfo(&g_Region[REGION_HEAP], 4, 5))) {
+        fatalSimple(MAKERESULT(MODULE_LIBNX, LIBNX_BADGETINFO));
+    }
+
+    // Failure is OK, happens on 1.0.0
+    // In that case, g_UnkRegion will default to (0, 0).
+    _GetRegionFromInfo(&g_Region[REGION_UNK], 14, 15);
 }
 
 void* virtmemReserve(size_t size) {
-    void* ret = g_VirtBase;
+    Result  rc;
+    MemInfo meminfo;
+    u32     pageinfo;
+    size_t  i;
 
     size = (size + 0xFFF) &~ 0xFFF;
-    g_VirtBase += size + 0x1000;
 
-    return ret;
+    u64 addr = g_CurrentAddr;
+    while (1)
+    {
+        // Add a guard page.
+        addr += 0x1000;
+
+        // If we go outside address space, let's go back to start.
+        if (!_InRegion(&g_AddressSpace, addr)) {
+            addr = g_AddressSpace.start;
+        }
+        // Query information about address.
+        rc = svcQueryMemory(&meminfo, &pageinfo, addr);
+
+        if (R_FAILED(rc)) {
+            fatalSimple(MAKERESULT(MODULE_LIBNX, LIBNX_BADQUERYMEMORY));
+        }
+
+        if (meminfo.memorytype != 0) {
+            // Address is already taken, let's move past it.
+            addr = meminfo.base_addr + meminfo.size;
+            continue;
+        }
+
+        if (size > meminfo.size) {
+            // We can't fit in this region, let's move past it.
+            addr = meminfo.base_addr + meminfo.size;
+            continue;
+        }
+
+        // Check if we end up in a reserved region.
+        for(i=0; i<REGION_MAX; i++)
+        {
+            u64 end = addr + size - 1;
+
+            if (_InRegion(&g_Region[i], addr)) {
+                break;
+            }
+
+            if (_InRegion(&g_Region[i], end)) {
+                break;
+            }
+        }
+
+        // Did we?
+        if (i != REGION_MAX) {
+            addr = g_Region[i].end;
+            continue;
+        }
+
+        // Not in a reserved region, we're good to go!
+        break;
+    }
+
+    g_CurrentAddr = addr + size;
+    return (void*) addr;
 }
 
 void  virtmemFree(void* addr, size_t size) {
-    (void) addr;
-    (void) size;
+    IGNORE_ARG(addr);
+    IGNORE_ARG(size);
 }