add raw mmap/mprotect access

library/Process-darwin.cpp

@@ -305,3 +305,28 @@ bool Process::setPermisions(const t_memrange & range,const t_memrange &trgrange)
 
     return result==0;
 }
+
+// returns -1 on error
+void* Process::memAlloc(const int length)
+{
+    return mmap(0, length, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
+}
+
+int Process::memDealloc(const void *ptr, const int length)
+{
+    return munmap(ptr, length);
+}
+
+int Process::memProtect(const void *ptr, const int length, const int prot)
+{
+    int prot_native = 0;
+
+    if (prot & Process::MemProt::READ)
+        prot_native |= PROT_READ;
+    if (prot & Process::MemProt::WRITE)
+        prot_native |= PROT_WRITE;
+    if (prot & Process::MemProt::EXEC)
+        prot_native |= PROT_EXEC;
+
+    return mprotect(ptr, length, prot_native);
+}

library/Process-linux.cpp

@@ -236,3 +236,28 @@ bool Process::setPermisions(const t_memrange & range,const t_memrange &trgrange)
 
     return result==0;
 }
+
+// returns -1 on error
+void* Process::memAlloc(const int length)
+{
+    return mmap(0, length, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+}
+
+int Process::memDealloc(void *ptr, const int length)
+{
+    return munmap(ptr, length);
+}
+
+int Process::memProtect(void *ptr, const int length, const int prot)
+{
+    int prot_native = 0;
+
+    if (prot & Process::MemProt::READ)
+        prot_native |= PROT_READ;
+    if (prot & Process::MemProt::WRITE)
+        prot_native |= PROT_WRITE;
+    if (prot & Process::MemProt::EXEC)
+        prot_native |= PROT_EXEC;
+
+    return mprotect(ptr, length, prot_native);
+}

library/Process-windows.cpp

@@ -473,3 +473,42 @@ bool Process::setPermisions(const t_memrange & range,const t_memrange &trgrange)
 
     return result;
 }
+
+void* Process::memAlloc(const int length)
+{
+    void *ret;
+    // returns 0 on error
+    ret = VirtualAlloc(0, length, MEM_RESERVE|MEM_COMMIT, PAGE_READWRITE);
+    if (!ret)
+        ret = (void*)-1;
+    return ret;
+}
+
+int Process::memDealloc(const void *ptr, const int length)
+{
+    // can only free the whole region at once
+    // vfree returns 0 on error
+    return !VirtualFree(ptr, 0, MEM_RELEASE)
+}
+
+int Process::memProtect(const void *ptr, const int length, const int prot)
+{
+    int prot_native = 0;
+    int old_prot = 0;
+
+    // only support a few constant combinations
+    if (prot == 0)
+        prot_native = PAGE_NOACCESS;
+    else if (prot == Process::MemProt::READ)
+        prot_native = PAGE_READONLY;
+    else if (prot == Process::MemProt::READ | Process::MemProt::WRITE)
+        prot_native = PAGE_READWRITE;
+    else if (prot == Process::MemProt::READ | Process::MemProt::WRITE | Process::MemProt::EXECUTE)
+        prot_native = PAGE_EXECUTE_READWRITE;
+    else if (prot == Process::MemProt::READ | Process::MemProt::EXECUTE)
+        prot_native = PAGE_EXECUTE_READ;
+    else
+        return -1;
+
+    return !VirtualProtect(ptr, length, prot_native, &old_prot);
+}

library/include/MemAccess.h

@@ -291,6 +291,27 @@ namespace DFHack
 
             /// write a possibly read-only memory area
             bool patchMemory(void *target, const void* src, size_t count);
+
+            /// allocate new memory pages for code or stuff
+            /// returns -1 on error (0 is a valid address)
+            void* memAlloc(const int length);
+
+            /// free memory pages from memAlloc
+            /// should have length = alloced length for portability
+            /// returns 0 on success
+            int memDealloc(void *ptr, const int length);
+
+            /// change memory page permissions
+            /// prot is a bitwise OR of the MemProt enum
+            /// returns 0 on success
+            int memProtect(void *ptr, const int length, const int prot);
+
+            enum MemProt {
+                READ = 1,
+                WRITE = 2,
+                EXEC = 4
+            };
+
     private:
         VersionInfo * my_descriptor;
         PlatformSpecific *d;