swissChili | e20b79b | 2021-03-17 21:20:13 -0700 | [diff] [blame^] | 1 | #include "task.h" |
| 2 | #include "alloc.h" |
| 3 | #include "io.h" |
| 4 | #include "paging.h" |
| 5 | |
| 6 | uint clone_page_table(uint table) |
| 7 | { |
| 8 | // is this table a 4mb mapping OR is it not mapped? |
| 9 | // See Intel manual volume 3 figure 4-4. |
| 10 | |
| 11 | if (table & 1 << 7 || !(table & 1)) |
| 12 | { |
| 13 | // if so, return as is, 4mb mappings only used by kernel and should |
| 14 | // be mapped to the same location |
| 15 | return table; |
| 16 | } |
| 17 | else |
| 18 | { |
| 19 | // else, look for the used pages in this table, copy them to a new |
| 20 | // frame, and store them in a new table, then return that table |
| 21 | // TODO: add copy on write |
| 22 | |
| 23 | uint new_p; |
| 24 | uint *new = kmalloc_ap(sizeof(uint[1024]), (void **)&new_p); |
| 25 | |
| 26 | // We don't care about the lower 12 bits, just want the address |
| 27 | uint *old_virt = PHYS_TO_VIRT((uint *)(table ^ 0xfff)); |
| 28 | |
| 29 | for (int i = 0; i < 1024; i++) |
| 30 | { |
| 31 | if (old_virt[i] & 1) |
| 32 | { |
| 33 | // If mapped |
| 34 | |
| 35 | // again, don't care about bottom 12 bits |
| 36 | uchar *old_page = PHYS_TO_VIRT(old_virt[i] ^ 0xfff); |
| 37 | |
| 38 | alloc_frame(&new[i], BOOL(old_virt[i] & 1 << 2), |
| 39 | BOOL(old_virt[i] & 1 << 1)); |
| 40 | |
| 41 | uchar *new_page = PHYS_TO_VIRT(new[i] ^ 0xfff); |
| 42 | memcpy(new_page, old_page, 0x1000); |
| 43 | } |
| 44 | } |
| 45 | |
| 46 | return new_p | (table & 0xfff); // same lower 12 bits |
| 47 | } |
| 48 | } |
| 49 | |
| 50 | uint *clone_page_directory(uint *dir) |
| 51 | { |
| 52 | uint new_p; |
| 53 | uint *new = kmalloc_ap(sizeof(uint[1024]), (void **)&new_p); |
| 54 | |
| 55 | for (int i = 0; i < 1024; i++) |
| 56 | { |
| 57 | new[i] = clone_page_table(dir[i]); |
| 58 | } |
| 59 | |
| 60 | return new; |
| 61 | } |