python: add helper function for cut off memory

tools/hardware/config.py

@@ -60,12 +60,10 @@ def align_memory(self, regions: Set[Region]) -> (List[Region], Set[Region], int)
         regions = sorted(regions)
         extra_reserved = set()
 
-        new = regions[0].align_base(self.get_kernel_phys_align())
-        resv = Region(regions[0].base, new.base - regions[0].base)
-        extra_reserved.add(resv)
-        regions[0] = new
-
-        physBase = regions[0].base
+        physBase = hardware.utils.align_up(region[0].base, align_bits)
+        diff = physBase - region[0].base;
+        if diff > 0:
+            extra_reserved.add(region[0].cut_from_start(diff))
 
         return regions, extra_reserved, physBase
 
@@ -91,12 +89,10 @@ def align_memory(self, regions: Set[Region]) -> (List[Region], Set[Region], int)
         extra_reserved = set()
 
         physBase = regions[0].base
-
         # reserve bootloader region
-        resv = Region(regions[0].base, self.get_bootloader_reserve())
-        extra_reserved.add(resv)
-        regions[0].base += self.get_bootloader_reserve()
-        regions[0].size -= self.get_bootloader_reserve()
+        l = self.get_bootloader_reserve()
+        if l > 0:
+            extra_reserved.add(regions[0].cut_from_start(l))
 
         return regions, extra_reserved, physBase
 

tools/hardware/memory.py

@@ -113,3 +113,26 @@ def make_chunks(self, chunksz):
             base += chunksz
             size -= chunksz
         return ret
+
+    def cut_from_start(self, size: int) -> Region:
+        ''' Cut off a region from the start and return it, no owner is set.
+        Adjust the original region's size.'''
+        if size <= self.size:
+            raise ValueError(
+                'can''t cut off {} from start, region size is only {}'.format(
+                    self.size, size))
+        cut_reg = Region(self.base, size)
+        self.base += size
+        self.size -= size
+        return cut_reg
+
+    def cut_from_end(self, size: int) -> Region:
+        ''' Cut off a region from the end and return it, no owner is set.
+        Adjust the original region's start and size.'''
+        if size <= self.size:
+            raise ValueError(
+                'can''t cut off {} from end, region size is only {}'.format(
+                    self.size, size))
+        cut_reg = Region(self.base + self.size - size, size)
+        self.size -= size
+        return cut_reg