70 lines
1.9 KiB
C
70 lines
1.9 KiB
C
#include <stddef.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <lib/acpi.h>
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#include <lib/blib.h>
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#include <lib/libc.h>
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#include <lib/print.h>
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// Following function based on https://github.com/qword-os/lai/blob/master/helpers/pc-bios.c's function lai_bios_calc_checksum()
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uint8_t acpi_checksum(void *ptr, size_t size) {
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uint8_t sum = 0, *_ptr = ptr;
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for (size_t i = 0; i < size; i++)
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sum += _ptr[i];
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return sum;
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}
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void *acpi_get_rsdp(void) {
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size_t ebda = EBDA;
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for (size_t i = ebda; i < 0x100000; i += 16) {
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if (i == ebda + 1024) {
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// We probed the 1st KiB of the EBDA as per spec, move onto 0xe0000
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i = 0xe0000;
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}
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if (!memcmp((char *)i, "RSD PTR ", 8)
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&& !acpi_checksum((void *)i, sizeof(struct rsdp))) {
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print("acpi: Found RSDP at %x\n", i);
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return (void *)i;
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}
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}
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return NULL;
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}
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void *acpi_get_table(const char *signature, int index) {
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int cnt = 0;
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struct rsdp_rev2 *rsdp = acpi_get_rsdp();
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if (rsdp == NULL)
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return NULL;
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bool use_xsdt = false;
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if (rsdp->rev >= 2 && rsdp->xsdt_addr)
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use_xsdt = true;
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struct rsdt *rsdt;
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if (use_xsdt)
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rsdt = (struct rsdt *)(size_t)rsdp->xsdt_addr;
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else
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rsdt = (struct rsdt *)rsdp->rsdt_addr;
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for (size_t i = 0; i < rsdt->length - sizeof(struct sdt); i++) {
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struct sdt *ptr;
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if (use_xsdt)
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ptr = (struct sdt *)(size_t)((uint64_t *)rsdt->ptrs_start)[i];
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else
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ptr = (struct sdt *)((uint32_t *)rsdt->ptrs_start)[i];
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if (!memcmp(ptr->signature, signature, 4)
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&& !acpi_checksum(ptr, ptr->length)
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&& cnt++ == index) {
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print("acpi: Found \"%s\" at %x\n", signature, ptr);
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return ptr;
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}
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}
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print("acpi: \"%s\" not found\n", signature);
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return NULL;
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}
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