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Limit BIOS bootloader's max_phys_addr to 4 GiB #260

Merged
merged 2 commits into from
Sep 25, 2022
Merged

Limit BIOS bootloader's max_phys_addr to 4 GiB #260

merged 2 commits into from
Sep 25, 2022

Commits on Sep 22, 2022

  1. Limit BIOS bootloader's max_phys_addr to 4 GiB 

    When determining the maximum physical address for the BIOS bootloader's
identity mapping, we currently use the highest address in the E380
memory map, no matter how high it is. However, the bootloader runs in
protected mode, and therefore, it cannot address more than 4 GiB of
memory. We can save some time by not identity mapping addresses over 4
GiB, as the bootloader cannot address them anyway.

This commit changes the BIOS bootloader to skip addresses over 4 GiB
when determining the maximum physical address.

This is one of the changes described in issue rust-osdev#259.
    @hawkw
    hawkw committed Sep 22, 2022
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  2. Allow mapping part of a region if it crosses 4 GiB

    @hawkw
    hawkw committed Sep 22, 2022
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