1 files changed, 431 insertions, 0 deletions

diff --git a/src/mm/memory.c b/src/mm/memory.c
new file mode 100644
index 0000000..340a7fc
--- /dev/null
+++ b/src/mm/memory.c
@@ -0,0 +1,431 @@
+/*
+ *  linux/mm/memory.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+/*
+ * demand-loading started 01.12.91 - seems it is high on the list of
+ * things wanted, and it should be easy to implement. - Linus
+ */
+
+/*
+ * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
+ * pages started 02.12.91, seems to work. - Linus.
+ *
+ * Tested sharing by executing about 30 /bin/sh: under the old kernel it
+ * would have taken more than the 6M I have free, but it worked well as
+ * far as I could see.
+ *
+ * Also corrected some "invalidate()"s - I wasn't doing enough of them.
+ */
+
+#include <signal.h>
+
+#include <asm/system.h>
+
+#include <linux/sched.h>
+#include <linux/head.h>
+#include <linux/kernel.h>
+
+void do_exit(long code);
+
+static inline void oom(void)
+{
+        printk("out of memory\n\r");
+        do_exit(SIGSEGV);
+}
+
+#define invalidate() \
+__asm__("movl %%eax,%%cr3"::"a" (0))
+
+/* these are not to be changed without changing head.s etc */
+#define LOW_MEM 0x100000
+#define PAGING_MEMORY (15*1024*1024)
+#define PAGING_PAGES (PAGING_MEMORY>>12)
+#define MAP_NR(addr) (((addr)-LOW_MEM)>>12)
+#define USED 100
+
+#define CODE_SPACE(addr) ((((addr)+4095)&~4095) < \
+current->start_code + current->end_code)
+
+static long HIGH_MEMORY = 0;
+
+#define copy_page(from,to) \
+__asm__("cld ; rep ; movsl"::"S" (from),"D" (to),"c" (1024))
+
+static unsigned char mem_map [ PAGING_PAGES ] = {0,};
+
+/*
+ * Get physical address of first (actually last :-) free page, and mark it
+ * used. If no free pages left, return 0.
+ */
+unsigned long get_free_page(void)
+{
+register unsigned long __res asm("ax");
+
+__asm__("std ; repne ; scasb\n\t"
+        "jne 1f\n\t"
+        "movb $1,1(%%edi)\n\t"
+        "sall $12,%%ecx\n\t"
+        "addl %2,%%ecx\n\t"
+        "movl %%ecx,%%edx\n\t"
+        "movl $1024,%%ecx\n\t"
+        "leal 4092(%%edx),%%edi\n\t"
+        "rep ; stosl\n\t"
+        " movl %%edx,%%eax\n"
+        "1: cld"
+        :"=a" (__res)
+        :"0" (0),"i" (LOW_MEM),"c" (PAGING_PAGES),
+        "D" (mem_map+PAGING_PAGES-1)
+        );
+return __res;
+}
+
+/*
+ * Free a page of memory at physical address 'addr'. Used by
+ * 'free_page_tables()'
+ */
+void free_page(unsigned long addr)
+{
+        if (addr < LOW_MEM) return;
+        if (addr >= HIGH_MEMORY)
+                panic("trying to free nonexistent page");
+        addr -= LOW_MEM;
+        addr >>= 12;
+        if (mem_map[addr]--) return;
+        mem_map[addr]=0;
+        panic("trying to free free page");
+}
+
+/*
+ * This function frees a continuos block of page tables, as needed
+ * by 'exit()'. As does copy_page_tables(), this handles only 4Mb blocks.
+ */
+int free_page_tables(unsigned long from,unsigned long size)
+{
+        unsigned long *pg_table;
+        unsigned long * dir, nr;
+
+        if (from & 0x3fffff)
+                panic("free_page_tables called with wrong alignment");
+        if (!from)
+                panic("Trying to free up swapper memory space");
+        size = (size + 0x3fffff) >> 22;
+        dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
+        for ( ; size-->0 ; dir++) {
+                if (!(1 & *dir))
+                        continue;
+                pg_table = (unsigned long *) (0xfffff000 & *dir);
+                for (nr=0 ; nr<1024 ; nr++) {
+                        if (1 & *pg_table)
+                                free_page(0xfffff000 & *pg_table);
+                        *pg_table = 0;
+                        pg_table++;
+                }
+                free_page(0xfffff000 & *dir);
+                *dir = 0;
+        }
+        invalidate();
+        return 0;
+}
+
+/*
+ *  Well, here is one of the most complicated functions in mm. It
+ * copies a range of linerar addresses by copying only the pages.
+ * Let's hope this is bug-free, 'cause this one I don't want to debug :-)
+ *
+ * Note! We don't copy just any chunks of memory - addresses have to
+ * be divisible by 4Mb (one page-directory entry), as this makes the
+ * function easier. It's used only by fork anyway.
+ *
+ * NOTE 2!! When from==0 we are copying kernel space for the first
+ * fork(). Then we DONT want to copy a full page-directory entry, as
+ * that would lead to some serious memory waste - we just copy the
+ * first 160 pages - 640kB. Even that is more than we need, but it
+ * doesn't take any more memory - we don't copy-on-write in the low
+ * 1 Mb-range, so the pages can be shared with the kernel. Thus the
+ * special case for nr=xxxx.
+ */
+int copy_page_tables(unsigned long from,unsigned long to,long size)
+{
+        unsigned long * from_page_table;
+        unsigned long * to_page_table;
+        unsigned long this_page;
+        unsigned long * from_dir, * to_dir;
+        unsigned long nr;
+
+        if ((from&0x3fffff) || (to&0x3fffff))
+                panic("copy_page_tables called with wrong alignment");
+        from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
+        to_dir = (unsigned long *) ((to>>20) & 0xffc);
+        size = ((unsigned) (size+0x3fffff)) >> 22;
+        for( ; size-->0 ; from_dir++,to_dir++) {
+                if (1 & *to_dir)
+                        panic("copy_page_tables: already exist");
+                if (!(1 & *from_dir))
+                        continue;
+                from_page_table = (unsigned long *) (0xfffff000 & *from_dir);
+                if (!(to_page_table = (unsigned long *) get_free_page()))
+                        return -1;      /* Out of memory, see freeing */
+                *to_dir = ((unsigned long) to_page_table) | 7;
+                nr = (from==0)?0xA0:1024;
+                for ( ; nr-- > 0 ; from_page_table++,to_page_table++) {
+                        this_page = *from_page_table;
+                        if (!(1 & this_page))
+                                continue;
+                        this_page &= ~2;
+                        *to_page_table = this_page;
+                        if (this_page > LOW_MEM) {
+                                *from_page_table = this_page;
+                                this_page -= LOW_MEM;
+                                this_page >>= 12;
+                                mem_map[this_page]++;
+                        }
+                }
+        }
+        invalidate();
+        return 0;
+}
+
+/*
+ * This function puts a page in memory at the wanted address.
+ * It returns the physical address of the page gotten, 0 if
+ * out of memory (either when trying to access page-table or
+ * page.)
+ */
+unsigned long put_page(unsigned long page,unsigned long address)
+{
+        unsigned long tmp, *page_table;
+
+/* NOTE !!! This uses the fact that _pg_dir=0 */
+
+        if (page < LOW_MEM || page >= HIGH_MEMORY)
+                printk("Trying to put page %p at %p\n",page,address);
+        if (mem_map[(page-LOW_MEM)>>12] != 1)
+                printk("mem_map disagrees with %p at %p\n",page,address);
+        page_table = (unsigned long *) ((address>>20) & 0xffc);
+        if ((*page_table)&1)
+                page_table = (unsigned long *) (0xfffff000 & *page_table);
+        else {
+                if (!(tmp=get_free_page()))
+                        return 0;
+                *page_table = tmp|7;
+                page_table = (unsigned long *) tmp;
+        }
+        page_table[(address>>12) & 0x3ff] = page | 7;
+/* no need for invalidate */
+        return page;
+}
+
+void un_wp_page(unsigned long * table_entry)
+{
+        unsigned long old_page,new_page;
+
+        old_page = 0xfffff000 & *table_entry;
+        if (old_page >= LOW_MEM && mem_map[MAP_NR(old_page)]==1) {
+                *table_entry |= 2;
+                invalidate();
+                return;
+        }
+        if (!(new_page=get_free_page()))
+                oom();
+        if (old_page >= LOW_MEM)
+                mem_map[MAP_NR(old_page)]--;
+        *table_entry = new_page | 7;
+        invalidate();
+        copy_page(old_page,new_page);
+}       
+
+/*
+ * This routine handles present pages, when users try to write
+ * to a shared page. It is done by copying the page to a new address
+ * and decrementing the shared-page counter for the old page.
+ *
+ * If it's in code space we exit with a segment error.
+ */
+void do_wp_page(unsigned long error_code,unsigned long address)
+{
+#if 0
+/* we cannot do this yet: the estdio library writes to code space */
+/* stupid, stupid. I really want the libc.a from GNU */
+        if (CODE_SPACE(address))
+                do_exit(SIGSEGV);
+#endif
+        un_wp_page((unsigned long *)
+                (((address>>10) & 0xffc) + (0xfffff000 &
+                *((unsigned long *) ((address>>20) &0xffc)))));
+
+}
+
+void write_verify(unsigned long address)
+{
+        unsigned long page;
+
+        if (!( (page = *((unsigned long *) ((address>>20) & 0xffc)) )&1))
+                return;
+        page &= 0xfffff000;
+        page += ((address>>10) & 0xffc);
+        if ((3 & *(unsigned long *) page) == 1)  /* non-writeable, present */
+                un_wp_page((unsigned long *) page);
+        return;
+}
+
+void get_empty_page(unsigned long address)
+{
+        unsigned long tmp;
+
+        if (!(tmp=get_free_page()) || !put_page(tmp,address)) {
+                free_page(tmp);         /* 0 is ok - ignored */
+                oom();
+        }
+}
+
+/*
+ * try_to_share() checks the page at address "address" in the task "p",
+ * to see if it exists, and if it is clean. If so, share it with the current
+ * task.
+ *
+ * NOTE! This assumes we have checked that p != current, and that they
+ * share the same executable.
+ */
+static int try_to_share(unsigned long address, struct task_struct * p)
+{
+        unsigned long from;
+        unsigned long to;
+        unsigned long from_page;
+        unsigned long to_page;
+        unsigned long phys_addr;
+
+        from_page = to_page = ((address>>20) & 0xffc);
+        from_page += ((p->start_code>>20) & 0xffc);
+        to_page += ((current->start_code>>20) & 0xffc);
+/* is there a page-directory at from? */
+        from = *(unsigned long *) from_page;
+        if (!(from & 1))
+                return 0;
+        from &= 0xfffff000;
+        from_page = from + ((address>>10) & 0xffc);
+        phys_addr = *(unsigned long *) from_page;
+/* is the page clean and present? */
+        if ((phys_addr & 0x41) != 0x01)
+                return 0;
+        phys_addr &= 0xfffff000;
+        if (phys_addr >= HIGH_MEMORY || phys_addr < LOW_MEM)
+                return 0;
+        to = *(unsigned long *) to_page;
+        if (!(to & 1)) {
+                if ((to = get_free_page()))
+                        *(unsigned long *) to_page = to | 7;
+                else
+                        oom();
+        }
+        to &= 0xfffff000;
+        to_page = to + ((address>>10) & 0xffc);
+        if (1 & *(unsigned long *) to_page)
+                panic("try_to_share: to_page already exists");
+/* share them: write-protect */
+        *(unsigned long *) from_page &= ~2;
+        *(unsigned long *) to_page = *(unsigned long *) from_page;
+        invalidate();
+        phys_addr -= LOW_MEM;
+        phys_addr >>= 12;
+        mem_map[phys_addr]++;
+        return 1;
+}
+
+/*
+ * share_page() tries to find a process that could share a page with
+ * the current one. Address is the address of the wanted page relative
+ * to the current data space.
+ *
+ * We first check if it is at all feasible by checking executable->i_count.
+ * It should be >1 if there are other tasks sharing this inode.
+ */
+static int share_page(unsigned long address)
+{
+        struct task_struct ** p;
+
+        if (!current->executable)
+                return 0;
+        if (current->executable->i_count < 2)
+                return 0;
+        for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
+                if (!*p)
+                        continue;
+                if (current == *p)
+                        continue;
+                if ((*p)->executable != current->executable)
+                        continue;
+                if (try_to_share(address,*p))
+                        return 1;
+        }
+        return 0;
+}
+
+void do_no_page(unsigned long error_code,unsigned long address)
+{
+        int nr[4];
+        unsigned long tmp;
+        unsigned long page;
+        int block,i;
+
+        address &= 0xfffff000;
+        tmp = address - current->start_code;
+        if (!current->executable || tmp >= current->end_data) {
+                get_empty_page(address);
+                return;
+        }
+        if (share_page(tmp))
+                return;
+        if (!(page = get_free_page()))
+                oom();
+/* remember that 1 block is used for header */
+        block = 1 + tmp/BLOCK_SIZE;
+        for (i=0 ; i<4 ; block++,i++)
+                nr[i] = bmap(current->executable,block);
+        bread_page(page,current->executable->i_dev,nr);
+        i = tmp + 4096 - current->end_data;
+        tmp = page + 4096;
+        while (i-- > 0) {
+                tmp--;
+                *(char *)tmp = 0;
+        }
+        if (put_page(page,address))
+                return;
+        free_page(page);
+        oom();
+}
+
+void mem_init(long start_mem, long end_mem)
+{
+        int i;
+
+        HIGH_MEMORY = end_mem;
+        for (i=0 ; i<PAGING_PAGES ; i++)
+                mem_map[i] = USED;
+        i = MAP_NR(start_mem);
+        end_mem -= start_mem;
+        end_mem >>= 12;
+        while (end_mem-->0)
+                mem_map[i++]=0;
+}
+
+void calc_mem(void)
+{
+        int i,j,k,free=0;
+        long * pg_tbl;
+
+        for(i=0 ; i<PAGING_PAGES ; i++)
+                if (!mem_map[i]) free++;
+        printk("%d pages free (of %d)\n\r",free,PAGING_PAGES);
+        for(i=2 ; i<1024 ; i++) {
+                if (1&pg_dir[i]) {
+                        pg_tbl=(long *) (0xfffff000 & pg_dir[i]);
+                        for(j=k=0 ; j<1024 ; j++)
+                                if (pg_tbl[j]&1)
+                                        k++;
+                        printk("Pg-dir[%d] uses %d pages\n",i,k);
+                }
+        }
+}