memlayout.h

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Physical memory layout

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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.

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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

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qemu puts UART registers here in physical memory.

#define UART0 0x10000000L
#define UART0_IRQ 10

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virtio mmio interface

#define VIRTIO0 0x10001000
#define VIRTIO0_IRQ 1

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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)

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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)

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map the trampoline page to the highest address, in both user and kernel space.

#define TRAMPOLINE (MAXVA - PGSIZE)

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map kernel stacks beneath the trampoline, each surrounded by invalid guard pages.

#define KSTACK(p) (TRAMPOLINE - ((p)+1)* 2*PGSIZE)

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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)