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limine: Do not drop unconditional mapping of first 4GiB

This commit is contained in:
mintsuki 2023-07-25 02:54:00 -05:00
parent 296aba6bb7
commit 303592f9e7
2 changed files with 26 additions and 10 deletions
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3
PROTOCOL.md
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@ -98,6 +98,9 @@ below.
Alongside the loaded kernel, the bootloader will set up memory mappings such
that every usable, bootloader reclaimable, framebuffer, or kernel/modules
memory map region is mapped at HHDM offset + its physical address.
Additionally, the whole 0->4GiB physical memory region will also be mapped
at HHDM offset + physical address, regardless of the contents of the
memory map.
These mappings are supervisor, read, write, execute (-rwx), and they use
WB caching (on x86_64).

33
common/protos/limine.c
View File

@ -69,12 +69,18 @@ static pagemap_t build_pagemap(int paging_mode, bool nx, struct elf_range *range
for (size_t i = 0; i < _memmap_entries; i++)
_memmap[i] = memmap[i];
// Map 0->4GiB range to HHDM
for (uint64_t i = 0; i < 0x100000000; i += 0x40000000) {
map_page(pagemap, direct_map_offset + i, i, VMM_FLAG_WRITE, Size1GiB);
}
print_memmap(memmap, memmap_entries);
// Map all free memory regions to the higher half direct map offset
for (size_t i = 0; i < _memmap_entries; i++) {
if (_memmap[i].type != MEMMAP_USABLE
&& _memmap[i].type != MEMMAP_BOOTLOADER_RECLAIMABLE
&& _memmap[i].type != MEMMAP_KERNEL_AND_MODULES
&& _memmap[i].type != MEMMAP_FRAMEBUFFER) {
&& _memmap[i].type != MEMMAP_KERNEL_AND_MODULES) {
continue;
}
@ -82,24 +88,25 @@ static pagemap_t build_pagemap(int paging_mode, bool nx, struct elf_range *range
uint64_t length = _memmap[i].length;
uint64_t top = base + length;
if (base < 0x100000000) {
base = 0x100000000;
}
if (base >= top) {
continue;
}
uint64_t aligned_base = ALIGN_DOWN(base, 0x40000000);
uint64_t aligned_top = ALIGN_UP(top, 0x40000000);
uint64_t aligned_length = aligned_top - aligned_base;
for (uint64_t j = 0; j < aligned_length; j += 0x40000000) {
uint64_t page = aligned_base + j;
#if defined (__x86_64__) || defined (__i386__)
// XXX we do this as a quick and dirty way to switch to the higher half
if (_memmap[i].type == MEMMAP_BOOTLOADER_RECLAIMABLE) {
map_page(pagemap, page, page, VMM_FLAG_WRITE, Size1GiB);
}
#endif
map_page(pagemap, direct_map_offset + page, page, VMM_FLAG_WRITE, Size1GiB);
}
}
// Map the framebuffer as uncacheable
#if defined (__aarch64__)
// Map the framebuffer with appropriate permissions
for (size_t i = 0; i < _memmap_entries; i++) {
if (_memmap[i].type != MEMMAP_FRAMEBUFFER) {
continue;
@ -118,6 +125,12 @@ static pagemap_t build_pagemap(int paging_mode, bool nx, struct elf_range *range
map_page(pagemap, direct_map_offset + page, page, VMM_FLAG_WRITE | VMM_FLAG_FB, Size4KiB);
}
}
// XXX we do this as a quick and dirty way to switch to the higher half
#if defined (__x86_64__) || defined (__i386__)
for (uint64_t i = 0; i < 0x100000000; i += 0x40000000) {
map_page(pagemap, i, i, VMM_FLAG_WRITE, Size1GiB);
}
#endif
return pagemap;