d0f7acf9eb
An x86-64 operating system built from xv6, now largely rewritten: SMP, a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF rasteriser, and a Linux-numbered syscall ABI. No history before this point -- the tree was never under version control. This commit exists so the rename that follows has something to undo to.
49 lines
1.8 KiB
C
49 lines
1.8 KiB
C
#pragma once
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// Memory layout
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#define EXTMEM 0x100000 // Start of extended memory
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// Top of usable physical memory. A *variable*, read from the firmware's E820
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// map at boot -- see kernel/arch/x86_64/e820.c. It used to be the constant
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// below, which was not a limit on what the kernel used but an assertion that
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// exactly 224 MB existed: less and the allocator walked off the end of RAM,
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// more and it was invisible.
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//
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// The macro spelling is kept so that the twenty-odd call sites read the same as
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// they always did. It must not be used before e820_init(), which runs first
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// thing in main() for that reason.
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#ifndef __ASSEMBLER__
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extern uint64 phystop;
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#define PHYSTOP phystop
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#endif
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// What to assume when the firmware gives us nothing usable: the old constant,
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// so that path behaves exactly as the kernel always did.
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#define PHYSTOP_FALLBACK 0xE000000ULL
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// kvmalloc() maps physical 0-4 GB as four 1 GB pages and marks the top one
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// uncached, because that is where PCI BARs and the framebuffer sit. 3 GB is
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// therefore the most that can be treated as RAM.
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#define PHYSTOP_MAX 0xC0000000ULL
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// Below this the kernel image, its page tables and the DMA arena do not fit.
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#define PHYSTOP_MIN (24ULL * 1024 * 1024)
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// Key addresses for address space layout
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#define KERNBASE 0xFFFF800000000000 // First kernel virtual address
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#define KERNLINK (KERNBASE+EXTMEM) // Address where kernel is linked
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#ifndef __ASSEMBLER__
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static inline addr_t v2p(void *a) {
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return ((addr_t)(a)) - ((addr_t)KERNBASE);
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}
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static inline void *p2v(addr_t a) {
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return (void *)((a) + ((addr_t)KERNBASE));
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}
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#endif
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#define V2P(a) (((addr_t) (a)) - KERNBASE)
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#define P2V(a) (((void *) (a)) + KERNBASE)
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#define V2P_WO(x) ((x) - KERNBASE) // same as V2P, but without casts
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#define P2V_WO(x) ((x) + KERNBASE) // same as P2V, but without casts
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