first commit

kernel/memlayout.h

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+// Physical memory layout
+
+// qemu -machine virt is set up like this,
+// based on qemu's hw/riscv/virt.c:
+//
+// 00001000 -- boot ROM, provided by qemu
+// 02000000 -- CLINT
+// 0C000000 -- PLIC
+// 10000000 -- uart0 
+// 10001000 -- virtio disk 
+// 80000000 -- boot ROM jumps here in machine mode
+//             -kernel loads the kernel here
+// unused RAM after 80000000.
+
+// the kernel uses physical memory thus:
+// 80000000 -- entry.S, then kernel text and data
+// end -- start of kernel page allocation area
+// PHYSTOP -- end RAM used by the kernel
+
+// qemu puts UART registers here in physical memory.
+#define UART0 0x10000000L
+#define UART0_IRQ 10
+
+// virtio mmio interface
+#define VIRTIO0 0x10001000
+#define VIRTIO0_IRQ 1
+
+// core local interruptor (CLINT), which contains the timer.
+#define CLINT 0x2000000L
+#define CLINT_MTIMECMP(hartid) (CLINT + 0x4000 + 8*(hartid))
+#define CLINT_MTIME (CLINT + 0xBFF8) // cycles since boot.
+
+// qemu puts platform-level interrupt controller (PLIC) here.
+#define PLIC 0x0c000000L
+#define PLIC_PRIORITY (PLIC + 0x0)
+#define PLIC_PENDING (PLIC + 0x1000)
+#define PLIC_SENABLE(hart) (PLIC + 0x2080 + (hart)*0x100)
+#define PLIC_SPRIORITY(hart) (PLIC + 0x201000 + (hart)*0x2000)
+#define PLIC_SCLAIM(hart) (PLIC + 0x201004 + (hart)*0x2000)
+
+// the kernel expects there to be RAM
+// for use by the kernel and user pages
+// from physical address 0x80000000 to PHYSTOP.
+#define KERNBASE 0x80000000L
+#define PHYSTOP (KERNBASE + 128*1024*1024)
+
+// map the trampoline page to the highest address,
+// in both user and kernel space.
+#define TRAMPOLINE (MAXVA - PGSIZE)
+
+// map kernel stacks beneath the trampoline,
+// each surrounded by invalid guard pages.
+#define KSTACK(p) (TRAMPOLINE - ((p)+1)* 2*PGSIZE)
+
+// User memory layout.
+// Address zero first:
+//   text
+//   original data and bss
+//   fixed-size stack
+//   expandable heap
+//   ...
+//   TRAPFRAME (p->trapframe, used by the trampoline)
+//   TRAMPOLINE (the same page as in the kernel)
+#define TRAPFRAME (TRAMPOLINE - PGSIZE)