From: AceVest <zhaoyanbai@126.com>
Date: Tue, 29 Apr 2014 15:00:00 +0000 (+0800)
Subject: fix privilege bug when init_paging; add sysexit for user program
X-Git-Tag: 0.3.0~77
X-Git-Url: http://zhaoyanbai.com/repos/?a=commitdiff_plain;h=eddd38aec8a167e79accec0f0bfffc01fe3763e3;p=kernel.git

fix privilege bug when init_paging; add sysexit for user program
---

diff --git a/boot/multiboot.S b/boot/multiboot.S
index 36675ab..de5acf1 100644
--- a/boot/multiboot.S
+++ b/boot/multiboot.S
@@ -74,7 +74,7 @@ kernel_entry:
     # Init Page Directory
     movl    %ebx,%edi
     movl    $init_pgt-KRNLADDR,%eax
-    addl    $7,%eax
+    addl    $3,%eax
     movl    $BOOT_INIT_PAGETBL_CNT,%ecx
 1:
     stosl
@@ -87,7 +87,7 @@ kernel_entry:
     movl    %eax,%edi
 
     movl    $init_pgt-KRNLADDR,%eax
-    addl    $7,%eax
+    addl    $3,%eax
     movl    $BOOT_INIT_PAGETBL_CNT,%ecx
 2:
     stosl
@@ -98,7 +98,7 @@ kernel_entry:
     movl    $init_pgt-KRNLADDR,%ebx
     movl    %ebx,%edi
     movl    $(BOOT_INIT_PAGETBL_CNT*1024),%ecx
-    movl    $0x07,%eax
+    movl    $3,%eax
     cld
 3:
     stosl
diff --git a/include/page.h b/include/page.h
index 7fc67f1..308da1a 100644
--- a/include/page.h
+++ b/include/page.h
@@ -23,10 +23,10 @@
 #define PAGE_WR     0x2
 #define PAGE_US     0x4
 
-#define PAGE_SHIFT  (12)
-#define PAGE_SIZE   (1UL << PAGE_SHIFT)
-#define PAGE_MASK   (~((1UL << PAGE_SHIFT)-1))
-#define PAGE_OFFSET (0xC0000000)
+#define PAGE_SHIFT      (12)
+#define PAGE_SIZE       (1UL << PAGE_SHIFT)
+#define PAGE_MASK       (~((1UL << PAGE_SHIFT)-1))
+#define PAGE_OFFSET     (0xC0000000)
 #define PAGE_PDE_CNT    1024
 #define PAGE_PTE_CNT    1024
 
diff --git a/kernel/syscall.S b/kernel/syscall.S
index 62bced0..780e76f 100644
--- a/kernel/syscall.S
+++ b/kernel/syscall.S
@@ -99,50 +99,15 @@ bad_syscnr:
     jmp    ret_from_bad_syscnr
 #endif
 
-#if 0
-syscall_entry:
-    /* 此时%esp存的是current的地址(&current) */
-    movl    (%esp),%esp        /* 获得current的值 */
-    addl    $TASK_SIZE, %esp    /* 指向PCB的顶部 */
-
-    pushl    %ds            /* %ss */
-    pushl    %ebp            /* %esp */
-    pushfl                /* %eflags */
-    pushl    $SELECTOR_USER_CS    /* %cs */
-    pushl    %gs:(,%ebp)        /* %eip */
-    pushl    %eax            /* sysc_nr */
-    SAVE_REGS
-
-    pushl    %eax
-    movw    %ss,%ax
-    movw    %ax, %ds
-    movw    %ax, %es
-    movw    %ax, %gs
-    movw    %ax, %fs
-    popl    %eax
-
-    call    *sysc_handler_table(,%eax,4)
-
-    movl    %eax, 0x18(%esp)    /* return value */
-
-    RESTORE_REGS
-    
-    movl    0x04(%esp), %edx    /* sysexit 参数 %eip */
-    movl    0x10(%esp), %ecx    /* sysexit 参数 %esp */
 
-    sti        /* sysenter会自动清除IF.貌似sysexit不会自动置位 */
-    sysexit
-#endif
-
-#if 0
-.global sysc_handler_table
-.extern sysc_write
-.extern    sysc_read_kbd
-.extern    sysc_reboot
-.extern    sysc_fork
-sysc_handler_table:
-.long    sysc_write
-.long    sysc_read_kbd
-.long    sysc_reboot
-.long    sysc_fork
-#endif
+# this routine should be load align by PAGE_SIZE
+# this page is shared by the kernel and userspace
+# the reason why i use this method is because of that the user program
+# no need to pay attention on the return address
+.section .sysexit
+.align 0x1000 
+.global sysexit
+sysexit:
+    nop
+    nop
+    ret
diff --git a/mm/mm.c b/mm/mm.c
index a853839..6ba689c 100644
--- a/mm/mm.c
+++ b/mm/mm.c
@@ -294,6 +294,19 @@ find_block:
 pde_t __initdata init_pgd[PDECNT_PER_PAGE]                       __attribute__((__aligned__(PAGE_SIZE)));
 pte_t __initdata init_pgt[PTECNT_PER_PAGE*BOOT_INIT_PAGETBL_CNT] __attribute__((__aligned__(PAGE_SIZE)));
 
+extern void sysexit();
+
+void set_page_shared(void *x)
+{
+    unsigned long addr = (unsigned long) x;
+    addr = PAGE_ALIGN(addr);
+    unsigned int npd = get_npd(addr);
+    init_pgd[npd] |= PAGE_US;
+
+    pte_t *pte = pa2va(init_pgd[npd] & PAGE_MASK);
+    pte[get_npt(addr)] |= PAGE_US;
+}
+
 void init_paging()
 {
     unsigned int i;
@@ -312,11 +325,11 @@ void init_paging()
 
             memset((void *)pgtb_addr, 0, PAGE_SIZE);
 
-            init_pgd[get_npd(page_addr)] = (pde_t)(pgtb_addr | PAGE_P | PAGE_WR | PAGE_US);
+            init_pgd[get_npd(page_addr)] = (pde_t)(pgtb_addr | PAGE_P | PAGE_WR);
         }
 
         pte = ((pte_t *) pa2va(pgtb_addr)) + ti;
-        *pte = (pte_t) (page_addr | PAGE_P | PAGE_WR | PAGE_US);
+        *pte = (pte_t) (page_addr | PAGE_P | PAGE_WR);
     }
 
 
@@ -327,6 +340,9 @@ void init_paging()
         init_pgd[i] = init_pgd[i-delta];
     }
 
+    // paging for user space
+    set_page_shared(sysexit);
+
     LOAD_CR3(init_pgd);
 }
 
diff --git a/scripts/link.ld b/scripts/link.ld
index 4095c8a..c1a3955 100644
--- a/scripts/link.ld
+++ b/scripts/link.ld
@@ -28,6 +28,7 @@ SECTIONS
         phys_addr = . - kernel_virtual_addr_start;
         *(.multiboot_header)
         *(.text)
+        *(.sysexit)
     }
     etext = .;
     .data : AT(phys_addr) ALIGN(0x1000) 
diff --git a/setup/setup.c b/setup/setup.c
index fff210a..479507b 100644
--- a/setup/setup.c
+++ b/setup/setup.c
@@ -60,7 +60,6 @@ void setup_kernel()
 
     setup_irqs();
 
-
     while(1); // TODO MODIFY CODE BELOW
 
     setup_tasks();