Clear memory on demand

kernel/context/memory.rs

@@ -1,3 +1,4 @@
+use arch::externs::memset;
 use arch::paging::{ActivePageTable, Page, PageIter, VirtualAddress};
 use arch::paging::entry::EntryFlags;
 
@@ -9,14 +10,14 @@ pub struct Memory {
 }
 
 impl Memory {
-    pub fn new(start: VirtualAddress, size: usize, flags: EntryFlags) -> Self {
+    pub fn new(start: VirtualAddress, size: usize, flags: EntryFlags, flush: bool, clear: bool) -> Self {
         let mut memory = Memory {
             start: start,
             size: size,
             flags: flags
         };
 
-        memory.map(true);
+        memory.map(flush, clear);
 
         memory
     }
@@ -35,7 +36,7 @@ impl Memory {
         Page::range_inclusive(start_page, end_page)
     }
 
-    pub fn map(&mut self, flush: bool) {
+    pub fn map(&mut self, flush: bool, clear: bool) {
         let mut active_table = unsafe { ActivePageTable::new() };
 
         //TODO: Clear pages?
@@ -45,6 +46,11 @@ impl Memory {
                 active_table.flush(page);
             }
         }
+
+        if clear {
+            assert!(flush);
+            unsafe { memset(self.start_address().get() as *mut u8, 0, self.size); }
+        }
     }
 
     pub fn unmap(&mut self, flush: bool) {
@@ -71,39 +77,35 @@ impl Memory {
         self.flags = new_flags;
     }
 
-    pub fn resize(&mut self, new_size: usize, flush: bool) {
+    pub fn resize(&mut self, new_size: usize, flush: bool, clear: bool) {
         let mut active_table = unsafe { ActivePageTable::new() };
 
-        //TODO: Clear pages?
         //TODO: Calculate page changes to minimize operations
         if new_size > self.size {
             let start_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size));
             let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + new_size - 1));
             for page in Page::range_inclusive(start_page, end_page) {
-                //println!("Map {:X}", page.start_address().get());
                 if active_table.translate_page(page).is_none() {
-                    //println!("Not found - mapping");
                     active_table.map(page, self.flags);
                     if flush {
                         active_table.flush(page);
                     }
-                } else {
-                    //println!("Found - skipping {:X}", page.start_address().get());
                 }
             }
+
+            if clear {
+                assert!(flush);
+                unsafe { memset((self.start.get() + self.size) as *mut u8, 0, new_size - self.size); }
+            }
         } else if new_size < self.size {
             let start_page = Page::containing_address(VirtualAddress::new(self.start.get() + new_size));
             let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size - 1));
             for page in Page::range_inclusive(start_page, end_page) {
-                //println!("Unmap {:X}", page.start_address().get());
                 if active_table.translate_page(page).is_some() {
-                    //println!("Found - unmapping");
                     active_table.unmap(page);
                     if flush {
                         active_table.flush(page);
                     }
-                } else {
-                    //println!("Not found - skipping {:X}", page.start_address().get());
                 }
             }
         }

kernel/elf.rs

@@ -10,7 +10,7 @@ use goblin::elf32::{header, program_header};
 #[cfg(target_arch = "x86_64")]
 use goblin::elf64::{header, program_header};
 
-use arch::externs::{memcpy, memset};
+use arch::externs::memcpy;
 use arch::paging::{entry, VirtualAddress};
 use arch::start::usermode;
 use context;
@@ -70,7 +70,9 @@ impl<'a> Elf<'a> {
                     let mut memory = context::memory::Memory::new(
                         VirtualAddress::new(segment.p_vaddr as usize),
                         segment.p_memsz as usize,
-                        entry::NO_EXECUTE | entry::WRITABLE
+                        entry::NO_EXECUTE | entry::WRITABLE,
+                        true,
+                        true
                     );
 
                     unsafe {
@@ -78,10 +80,6 @@ impl<'a> Elf<'a> {
                         memcpy(segment.p_vaddr as *mut u8,
                                 (self.data.as_ptr() as usize + segment.p_offset as usize) as *const u8,
                                 segment.p_filesz as usize);
-                        // Set BSS
-                        memset((segment.p_vaddr + segment.p_filesz) as *mut u8,
-                                0,
-                                (segment.p_memsz - segment.p_filesz) as usize);
                     }
 
                     let mut flags = entry::NO_EXECUTE | entry::USER_ACCESSIBLE;
@@ -107,11 +105,10 @@ impl<'a> Elf<'a> {
             context.stack = Some(context::memory::Memory::new(
                 VirtualAddress::new(stack_addr),
                 stack_size,
-                entry::NO_EXECUTE | entry::WRITABLE | entry::USER_ACCESSIBLE
+                entry::NO_EXECUTE | entry::WRITABLE | entry::USER_ACCESSIBLE,
+                true,
+                true
             ));
-
-            // Clear stack
-            unsafe { memset(stack_addr as *mut u8, 0, stack_size); }
         }
 
         // Go to usermode

kernel/syscall/process.rs

@@ -24,14 +24,16 @@ pub fn brk(address: usize) -> Result<usize> {
     } else if address >= arch::USER_HEAP_OFFSET {
         //TODO: out of memory errors
         if let Some(ref mut heap) = context.heap {
-            heap.resize(address - arch::USER_HEAP_OFFSET, true);
+            heap.resize(address - arch::USER_HEAP_OFFSET, true, true);
             return Ok(address);
         }
 
         context.heap = Some(context::memory::Memory::new(
             VirtualAddress::new(arch::USER_HEAP_OFFSET),
             address - arch::USER_HEAP_OFFSET,
-            entry::WRITABLE | entry::NO_EXECUTE | entry::USER_ACCESSIBLE
+            entry::WRITABLE | entry::NO_EXECUTE | entry::USER_ACCESSIBLE,
+            true,
+            true
         ));
 
         Ok(address)