搜索内存，找到RSDP

最新推荐文章于 2024-02-05 15:13:03 发布

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最新推荐文章于 2024-02-05 15:13:03 发布

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分类专栏： os imple 文章标签：操作系统 acpi

本文链接：https://blog.youkuaiyun.com/lzg666456/article/details/39552175

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源码摘自grub2。

acpi的rsdp保存在bios扩展数据区域或地址0xe0000~0xfffff区域内，通过搜索这两个地址区域找到rsdp。

struct acpi_rsdp_v10 *

machine_acpi_get_rsdpv1 (void)
{
   int ebda_len;
   uint8_t *ebda, *ptr;

   printf ("acpi:Looking for RSDP. Scanning EBDA\n");
   ebda = (uint8_t *) ((* ((uint16_t *) 0x40e)) << 4);
   ebda_len = * (uint16_t *) ebda;
   if (! ebda_len)
   return 0;
   for (ptr = ebda; ptr < ebda + 0x400; ptr += 16)
   if (memcmp (ptr, "RSD PTR ", 8) == 0
           && byte_checksum (ptr, sizeof (struct acpi_rsdp_v10)) == 0
           && ((struct acpi_rsdp_v10 *) ptr)->revision == 0)
   return (struct acpi_rsdp_v10 *) ptr;

   printf ("acpi:Looking for RSDP. Scanning BIOS\n");
   for (ptr = (uint8_t *) 0xe0000; ptr < (uint8_t *) 0x100000;
   ptr += 16)
   if (memcmp (ptr, "RSD PTR ", 8) == 0
           && byte_checksum (ptr, sizeof (struct acpi_rsdp_v10)) == 0
           && ((struct acpi_rsdp_v10 *) ptr)->revision == 0)
   return (struct acpi_rsdp_v10 *) ptr;
   return 0;
}

struct acpi_rsdp_v20 *
machine_acpi_get_rsdpv2 (void)
{
   int ebda_len;
   uint8_t *ebda, *ptr;

   printf ("acpi:Looking for RSDP. Scanning EBDA\n");
   ebda = (uint8_t *) ((* ((uint16_t *) 0x40e)) << 4);
   ebda_len = * (uint16_t *) ebda;
   if (! ebda_len)
   return 0;
   for (ptr = ebda; ptr < ebda + 0x400; ptr += 16)
   if (memcmp (ptr, "RSD PTR ", 8) == 0
           && byte_checksum (ptr, sizeof (struct acpi_rsdp_v10)) == 0
           && ((struct acpi_rsdp_v10 *) ptr)->revision != 0
           && ((struct acpi_rsdp_v20 *) ptr)->length < 1024
           && byte_checksum (ptr, ((struct acpi_rsdp_v20 *) ptr)->length)
           == 0)
   return (struct acpi_rsdp_v20 *) ptr;

   printf ("acpi:Looking for RSDP. Scanning BIOS\n");
   for (ptr = (uint8_t *) 0xe0000; ptr < (uint8_t *) 0x100000;
   ptr += 16)
   if (memcmp (ptr, "RSD PTR ", 8) == 0
           && byte_checksum (ptr, sizeof (struct acpi_rsdp_v10)) == 0
           && ((struct acpi_rsdp_v10 *) ptr)->revision != 0
           && ((struct acpi_rsdp_v20 *) ptr)->length < 1024
           && byte_checksum (ptr, ((struct acpi_rsdp_v20 *) ptr)->length)
           == 0)
   return (struct acpi_rsdp_v20 *) ptr;
   return 0;
}