From c6ffdc4814dcac6ffc5dc08f1cff571a59729ccc Mon Sep 17 00:00:00 2001 From: pjht Date: Thu, 30 Jul 2020 10:09:59 -0500 Subject: [PATCH] Paging now uses a bitfield to represnt a paging structure entry --- kernel/cpu/i386/paging.c | 115 ++++++++++++++++++++++++--------------- 1 file changed, 71 insertions(+), 44 deletions(-) diff --git a/kernel/cpu/i386/paging.c b/kernel/cpu/i386/paging.c index 279e8ad..aab37a2 100644 --- a/kernel/cpu/i386/paging.c +++ b/kernel/cpu/i386/paging.c @@ -11,28 +11,28 @@ #include /** - * \page pg_struct_entry Format of a paging structure entry - * The format of a page table/directiry entry is as following:
- * Bits 31-11 is the physical frame number the entry points to.
- * Bits 11-9 are availible for use by the OS.
- * Bit 8 is ignored.
- * Bit 7 is the page size in page directories, and must be 0 in page tables. If set to 1 in a page directory, it indicates 4MB pages.
- * Bit 6 is the dirty bit in page tables, and must be 0 in page directories. In page tabes, it is set to 1 by the CPU when the page is written to.
- * Bit 5 will be set to 1 by the CPU when the page is accessed.
- * Bit 4 indicates whether the page has it's cache disabled.
- * Bit 3 indictates whether write-through caching (when it is 1), or write-back caching, (when it is 0) is enabled.
- * Bit 2 indictaes whether user mode code can access the page.
- * Bit 1 indicates whether the page is writable.
- * Bit 0 indicates whether the entry is present. If it is 0, the CU ignores the other 31 bits of the entry.
- * Privlege bits in the entries are ANDed together, so the most restrictive privlege between the page directory and the page table wins. + * Represents an entry in a page table/directory. + * \note Privlege bits in the page directory and page table entries for a page are ANDed together, so the most restrictive privlege between the page directory and the page table wins. */ +typedef struct { + int pres:1; //!< Whether the page is present + int wr:1; //!< Whether the page is writeable + int usr:1; //!< Whether the page is accessible by user mode + int cachetype:1; //!< Cache type for the page. Write-through caching when 1, write-back caching when 0. + int cachedisable:1; //!< Whether caching is disabled + int accessed:1; //!< Whether the page has been accessed + int dirty:1; //!< Whether the page is dirty (has been written to) + int sz:1; //!< Page size + int osavail:4; //!< Availible for OS use + int pgno:20; //!< Physical page number this page maps to +} pg_struct_entry; -static uint32_t page_directory[1024] __attribute__((aligned(4096))); //!< The kernel process's page directory -static uint32_t kern_page_tables[NUM_KERN_FRAMES] __attribute__((aligned(4096))); //!< The page tables where the kernel binary is mapped in -static uint32_t kstack_page_tables[218*1024] __attribute__((aligned(4096))); //!< Page tables for thread kernel stacks -static uint32_t kmalloc_page_tables[4*1024] __attribute__((aligned(4096))); //!< Page tables for the kmalloc heap -static uint32_t* pagdirmap=(uint32_t*)0xFFFFF000; //!< Pointer to the page directory entries in the recursive mapping -static uint32_t* page_table_map=(uint32_t*)0xFFC00000; //!< Pointer to the page table entries in the recursive mapping +static pg_struct_entry page_directory[1024] __attribute__((aligned(4096))); //!< The kernel process's page directory +static pg_struct_entry kern_page_tables[NUM_KERN_FRAMES] __attribute__((aligned(4096))); //!< The page tables where the kernel binary is mapped in +static pg_struct_entry kstack_page_tables[218*1024] __attribute__((aligned(4096))); //!< Page tables for thread kernel stacks +static pg_struct_entry kmalloc_page_tables[4*1024] __attribute__((aligned(4096))); //!< Page tables for the kmalloc heap +static pg_struct_entry* pagdirmap=(pg_struct_entry*)0xFFFFF000; //!< Pointer to the page directory entries in the recursive mapping +static pg_struct_entry* page_table_map=(pg_struct_entry*)0xFFC00000; //!< Pointer to the page table entries in the recursive mapping /** * Checks whether a page is present * \param page The page number to check @@ -41,10 +41,10 @@ static uint32_t* page_table_map=(uint32_t*)0xFFC00000; //!< Pointer to the page static char is_page_present(size_t page) { int table=page>>10; page=page&0x3FF; - if ((pagdirmap[table]&0x1)==0) { + if (!pagdirmap[table].pres) { return 0; } - return page_table_map[page+1024*table]&0x1; + return page_table_map[page+1024*table].pres; } void map_pages(void* virt_addr_ptr,void* phys_addr_ptr,int num_pages,char usr,char wr) { @@ -53,16 +53,18 @@ void map_pages(void* virt_addr_ptr,void* phys_addr_ptr,int num_pages,char usr,ch int dir_entry=(virt_addr&0xFFC00000)>>22; int table_entry=(virt_addr&0x3FF000)>>12; for (int i=0;ipgno=(uint32_t)pmem_alloc(1)>>12; + entry->pres=1; + entry->usr=usr; + entry->wr=wr; } - int flags=1; - flags=flags|((wr&1)<<1); - flags=flags|((usr&1)<<2); - page_table_map[table_entry+1024*dir_entry]=phys_addr|flags; + pg_struct_entry* entry=&page_table_map[table_entry+1024*dir_entry]; + entry->pgno=phys_addr>>12; + entry->pres=1; + entry->usr=usr; + entry->wr=wr; table_entry++; if (table_entry==1024) { table_entry=0; @@ -131,10 +133,10 @@ void* virt_to_phys(void* virt_addr_arg) { if (!is_page_present(virt_addr>>12)) return NULL; int dir_idx=(virt_addr&0xFFC00000)>>22; int tbl_idx=(virt_addr&0x3FFC00)>>12; - if ((pagdirmap[dir_idx]&0x1)==0) { + if (!pagdirmap[dir_idx].pres) { return 0; } - return (void*)((page_table_map[tbl_idx+1024*dir_idx]&0xFFFFFC00)+offset); + return (void*)(((page_table_map[tbl_idx+1024*dir_idx].pgno)<<12)+offset); } @@ -153,12 +155,15 @@ static void invl_page(void* addr) { void* paging_new_address_space() { void* dir=pmem_alloc(1); - uint32_t* freepg=find_free_pages(1); + pg_struct_entry* freepg=find_free_pages(1); map_pages(freepg,dir,1,0,1); for (size_t i=0;i<1024;i++) { freepg[i]=page_directory[i]; } - freepg[1023]=((uint32_t)dir)|0x3; + pg_struct_entry* entry=&freepg[1023]; + entry->pres=1; + entry->wr=1; + entry->pgno=(uint32_t)dir>>12; unmap_pages(freepg,1); return dir; } @@ -172,8 +177,9 @@ void unmap_pages(void* start_virt,int num_pages) { int dir_entry=(virt_addr&0xFFC00000)>>22; int table_entry=(virt_addr&0x3FF000)>>12; for (int i=0;i<=num_pages;i++) { - if (page_table_map[dir_entry]&0x1) { - page_table_map[table_entry+1024*dir_entry]=0; + if (page_table_map[dir_entry].pres) { + pg_struct_entry* entry=&page_table_map[table_entry+1024*dir_entry]; + entry->pres=0; invl_page(start_virt+(i*1024)); table_entry++; if (table_entry==1024) { @@ -186,24 +192,40 @@ void unmap_pages(void* start_virt,int num_pages) { void paging_init() { for (size_t i=0;ipres=1; + entry->wr=1; + entry->pgno=i; } for (size_t i=0;i<218*1024;i++) { - kstack_page_tables[i]=0; + pg_struct_entry* entry=&kstack_page_tables[i]; + entry->pres=0; } for (size_t i=0;i<4*1024;i++) { - kmalloc_page_tables[i]=(uint32_t)pmem_alloc(1)|0x3; + pg_struct_entry* entry=&kmalloc_page_tables[i]; + entry->pres=1; + entry->wr=1; + entry->pgno=(uint32_t)pmem_alloc(1)>>12; } for (size_t i=0;ipres=1; + entry->wr=1; + entry->pgno=((uint32_t)entry_virt-0xC0000000)>>12; } - page_directory[985]=(uint32_t)(pmem_alloc(1024))|0x83; + // page_directory[985]=(uint32_t)(pmem_alloc(1024))|0x83; for (size_t i=0;i<4;i++) { uint32_t entry_virt=(uint32_t)&(kmalloc_page_tables[i*1024]); - page_directory[i+1018]=(entry_virt-0xC0000000)|0x3; + pg_struct_entry* entry=&page_directory[i+1018]; + entry->pres=1; + entry->wr=1; + entry->pgno=((uint32_t)entry_virt-0xC0000000)>>12; } - page_directory[1023]=((uint32_t)page_directory-0xC0000000)|0x3; + pg_struct_entry* entry=&page_directory[1023]; + entry->pres=1; + entry->wr=1; + entry->pgno=((uint32_t)page_directory-0xC0000000)>>12; load_address_space((uint32_t*)((uint32_t)page_directory-0xC0000000)); } @@ -212,3 +234,8 @@ void* get_address_space() { asm volatile("movl %%cr3, %%eax; movl %%eax, %0;":"=m"(address_space)::"%eax"); return address_space; } + +void dealloc_pages(int num_pages,void* addr) { + pmem_free((uint32_t)virt_to_phys(addr)>>12,num_pages); + unmap_pages(addr,num_pages); +}