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Avoid overwriting bootloader data

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This commit is contained in:
Thomas Lovén 2022-01-06 22:52:26 +01:00
parent 64df5d2b45
commit 60bb1bd039
3 changed files with 25 additions and 6 deletions
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17
src/kernel/boot/multiboot.c
View File

@ -1,6 +1,7 @@
#include <stdint.h> #include <stdint.h>
#include <multiboot.h> #include <multiboot.h>
#include <memory.h> #include <memory.h>
#include <debug.h>
// https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html // https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html
@ -39,7 +40,7 @@ struct fbinfo {
uint8_t data[]; uint8_t data[];
}__attribute__((packed)); }__attribute__((packed));
int parse_multiboot2(struct taglist *tags) static int parse_multiboot2(struct taglist *tags)
{ {
struct mmap *mmap; struct mmap *mmap;
@ -96,3 +97,17 @@ int multiboot_get_memory_area(size_t index, uintptr_t *start, uintptr_t *end, ui
*type = entry->type; *type = entry->type;
return 0; return 0;
} }
int multiboot_page_used(uintptr_t page)
{
#define within_page(st, l) (((uintptr_t)st + l) > page && (uintptr_t)st < (page + PAGE_SIZE))
if(
within_page(kernel_boot_data.bootloader, strlen(kernel_boot_data.bootloader)) ||
within_page(kernel_boot_data.commandline, strlen(kernel_boot_data.commandline)) ||
within_page(kernel_boot_data.mmap, kernel_boot_data.mmap_size) ||
0) {
debug("Page %x used\n", page);
return 1;
}
return 0;
}

1
src/kernel/include/multiboot.h
View File

@ -30,4 +30,5 @@ extern struct kernel_boot_data_st kernel_boot_data;
// boot/multiboot.c // boot/multiboot.c
int multiboot_init(uint64_t magic, void *mboot_info); int multiboot_init(uint64_t magic, void *mboot_info);
int multiboot_get_memory_area(size_t index, uintptr_t *start, uintptr_t *end, uint32_t *type); int multiboot_get_memory_area(size_t index, uintptr_t *start, uintptr_t *end, uint32_t *type);
int multiboot_page_used(uintptr_t page);
#endif #endif

13
src/kernel/memory/memory.c
View File

@ -19,9 +19,6 @@ void memory_init()
for(uint64_t p = start; p < end; p += PAGE_SIZE) for(uint64_t p = start; p < end; p += PAGE_SIZE)
{ {
if(p >= V2P(&kernel_start) && p < V2P(&kernel_end))
continue;
uint64_t vaddr = (uint64_t)P2V(p); uint64_t vaddr = (uint64_t)P2V(p);
uint64_t page = vmm_get_page(kernel_P4, vaddr); uint64_t page = vmm_get_page(kernel_P4, vaddr);
if(page == (uint64_t)-1 || !(page & PAGE_PRESENT)) if(page == (uint64_t)-1 || !(page & PAGE_PRESENT))
@ -30,8 +27,14 @@ void memory_init()
vmm_set_page(kernel_P4, vaddr, p, flags); vmm_set_page(kernel_P4, vaddr, p, flags);
} }
if(type == MMAP_FREE) if(type != MMAP_FREE)
pmm_free(p); continue;
if(p >= V2P(&kernel_start) && p < V2P(&kernel_end))
continue;
if(multiboot_page_used((uintptr_t)P2V(p)))
continue;
pmm_free(p);
} }
} }
} }