Fix RV32 multi-core: Setup page table for other cores.

kernel/src/arch/riscv32/memory.rs

@@ -1,4 +1,4 @@
-use core::slice;
+use core::{slice, mem};
 use memory::{active_table, FRAME_ALLOCATOR, init_heap, MemoryArea, MemoryAttr, MemorySet};
 use super::riscv::{addr::*, register::sstatus};
 use ucore_memory::PAGE_SIZE;
@@ -16,6 +16,13 @@ pub fn init() {
     remap_the_kernel();
 }
 
+pub fn init_other() {
+    unsafe {
+        sstatus::set_sum();         // Allow user memory access
+        asm!("csrw 0x180, $0; sfence.vma" :: "r"(SATP) :: "volatile");
+    }
+}
+
 fn init_frame_allocator() {
     use bit_allocator::BitAlloc;
     use core::ops::Range;
@@ -42,11 +49,15 @@ fn remap_the_kernel() {
     ms.push(MemoryArea::new_identity(srodata as usize, erodata as usize, MemoryAttr::default().readonly(), "rodata"));
     ms.push(MemoryArea::new_identity(sbss as usize, ebss as usize, MemoryAttr::default(), "bss"));
     unsafe { ms.activate(); }
-    use core::mem::forget;
+    unsafe { SATP = ms.token(); }
-    forget(ms);
+    mem::forget(ms);
     info!("kernel remap end");
 }
 
+// First core stores its SATP here.
+// Other cores load it later.
+static mut SATP: usize = 0;
+
 // Symbols provided by linker script
 extern {
     fn stext();

kernel/src/arch/riscv32/mod.rs

@@ -35,6 +35,7 @@ pub extern fn rust_main(hartid: usize, dtb: usize, hart_mask: usize) -> ! {
 
 fn others_main() -> ! {
     interrupt::init();
+    memory::init_other();
     timer::init();
     ::kmain();
 }