mirror of https://github.com/tailix/libkernaux.git
72 lines
2.8 KiB
C
72 lines
2.8 KiB
C
#include <kernaux/pfa.h>
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#include <assert.h>
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// Create PFA in some static memory area because typically you don't have memory
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// management in kernel without PFA.
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struct KernAux_PFA pfa;
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void example_main()
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{
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// In the earliest stage of kernel initialization mark all pages as
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// unavailable because you don't have memory map yet.
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KernAux_PFA_initialize(&pfa);
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// Let's assume that you have the following memory map now:
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// * [0 B; 64 KiB)
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// * [1 MiB; 4 MiB)
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// * [6 MiB; 128 MiB)
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// Mark these pages as available. Note that page is identified by any
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// address inside it. This is why you can subtract 1, not only
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// KERNAUX_PFA_PAGE_SIZE.
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KernAux_PFA_mark_available(&pfa, 0, 1024 * 64 - 1);
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KernAux_PFA_mark_available(&pfa, 1024 * 1024, 1024 * 1024 * 4 - 1);
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KernAux_PFA_mark_available(&pfa, 1024 * 1024 * 6, 1024 * 1024 * 128 - 1);
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// You can test page availability.
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assert(KernAux_PFA_is_available(&pfa, 1024 * 32)); // 32 KiB
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assert(!KernAux_PFA_is_available(&pfa, 1024 * 64)); // 64 KiB
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assert(KernAux_PFA_is_available(&pfa, 1024 * 1024)); // 1 MiB
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assert(!KernAux_PFA_is_available(&pfa, 1024 * 1024 * 6 // 6 MiB - 4 KiB
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- KERNAUX_PFA_PAGE_SIZE));
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assert(KernAux_PFA_is_available(&pfa, 1024 * 1024 * 128 // 128 MiB - 4 KiB
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- KERNAUX_PFA_PAGE_SIZE));
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assert(!KernAux_PFA_is_available(&pfa, 1024 * 1024 * 128)); // 128 MiB
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// When you have configured PFA, you can use it to allocate and free pages.
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{
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const size_t page_addr =
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KernAux_PFA_alloc_pages(&pfa, KERNAUX_PFA_PAGE_SIZE);
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assert(!KernAux_PFA_is_available(&pfa, page_addr));
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KernAux_PFA_free_pages(&pfa, page_addr, KERNAUX_PFA_PAGE_SIZE);
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assert(KernAux_PFA_is_available(&pfa, page_addr));
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}
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// You can also allocate multiple continuous pages.
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{
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const size_t page_addr =
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KernAux_PFA_alloc_pages(&pfa, 10 * KERNAUX_PFA_PAGE_SIZE);
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for (size_t index = 0, addr = page_addr; index < 10; ++index) {
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assert(!KernAux_PFA_is_available(&pfa, addr));
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addr += KERNAUX_PFA_PAGE_SIZE;
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}
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KernAux_PFA_free_pages(&pfa, page_addr, 10 * KERNAUX_PFA_PAGE_SIZE);
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for (size_t index = 0, addr = page_addr; index < 10; ++index) {
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assert(KernAux_PFA_is_available(&pfa, addr));
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addr += KERNAUX_PFA_PAGE_SIZE;
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}
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}
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// You can also request amounts of memory which are not factors of page
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// size.
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{
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const size_t page_addr = KernAux_PFA_alloc_pages(&pfa, 123);
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assert(!KernAux_PFA_is_available(&pfa, page_addr));
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KernAux_PFA_free_pages(&pfa, page_addr, 123);
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assert(KernAux_PFA_is_available(&pfa, page_addr));
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}
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}
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