Rewritten GDT descriptors

include/kernel/mm/gdt.h

@@ -32,6 +32,7 @@
 //----------------------------------------------------------------------------//
 
 #define IOMAP_SIZE (8 * 1024)
+#define TSS_TYPE 0x9
 
 //----------------------------------------------------------------------------//
 
@@ -92,6 +93,24 @@ struct GdtPtr_t
    ulong base;          // address of the first entry
 } __attribute__((__packed__));
 
+enum // For GdtEntry_t.accessed
+{
+    ACCESSEDSEG  = 1 << 0,
+    READABLE     = 1 << 1,
+    CONFORMING   = 1 << 2,
+    RESERVED     = 1 << 3,
+    RESERVED2    = 1 << 4,
+    USER         = 1 << 5,
+    USER2        = 1 << 6,
+    PRESENTSEG   = 1 << 7
+}; 
+
+enum // For GdtEntry_t.flags
+{
+    LONG         = 1 << 5,
+    LEGACY       = 1 << 6,
+};
+
 //----------------------------------------------------------------------------//
 
 //

kaleid/kernel/init/info.c

@@ -113,5 +113,7 @@ void BtDoSanityChecks(uint mbMagic) {
 
     DebugLog("Kernel successfully loaded at %p\n",
             BtLoaderInfo.kernelAddr);
+    DebugLog("Code segment : %#x\n",
+            BtLoaderInfo.codeSegment);
 }
 

kaleid/kernel/ke/syscall.asm

@@ -39,17 +39,12 @@ KeJumpToUserspace:
     ; rsi = entry point in user space
     ; rdx = user space stack
 
-    mov rax, 0x18 ; Selector 0x18 (User Data) + RPL 3
-    mov ds, rax
-    mov es, rax
-
 ; Build a fake iret frame
-    push rax          ; Selector 0x18 (User Data) + RPL 3
+    push QWORD 0x10   ; Selector 0x20 (User Data) + RPL 3
     push rdx          ; User space stack
     push QWORD 0x202  ; rflags = interrupt enable + reserved bit
-    push QWORD 0x20   ; Selector 0x20 (User Code) + RPL 3
+    push QWORD 0x08   ; Selector 0x18 (User Code) + RPL 3
     push rsi          ; Entry point in user space
-    
     iretq
 
 

kaleid/kernel/mm/gdt.c

@@ -43,27 +43,20 @@ void MmInitGdt(void)
     memzero((void *)&tss, sizeof(tss));
     
     // Kernel codeseg
-    gdt[1].lowLimit     = 0x0;
+    gdt[1].access       = PRESENTSEG | RESERVED | RESERVED2;
-    gdt[1].access       = 0x9A;
+    gdt[1].flags        = LONG;
-    gdt[1].flags        = 0x20;
     
     // Kernel dataseg
-    gdt[2].lowLimit     = 0x0;
+    gdt[2].access       = PRESENTSEG;
-    gdt[2].access       = 0x92;
-    gdt[2].flags        = 0x00;
-    
-    // User dataseg
-    gdt[3].lowLimit     = 0x0;
-    gdt[3].access       = 0xF2;
-    gdt[3].flags        = 0x20;
     
     // User codeseg
-    gdt[4].lowLimit     = 0x0;
+    gdt[3].access       = PRESENTSEG | RESERVED | RESERVED2 | USER | USER2;
-    gdt[4].access       = 0xFA;
+    gdt[3].flags        = LONG;
-    gdt[4].flags        = 0x20;
     
-    tssDesc.access          = 0x89;
+    // User dataseg
-    tssDesc.flags           = 0x40;
+    gdt[4].access       = PRESENTSEG | USER | USER2;
+
+    tssDesc.access          = TSS_TYPE | PRESENTSEG;
     tssDesc.lowBase         = (ulong)&tss & 0xFFFF;
     tssDesc.middleBase      = ((ulong)&tss >> 16) & 0xFF;
     tssDesc.highBase        = ((ulong)&tss >> 24) & 0xFF;
@@ -82,9 +75,9 @@ void MmInitGdt(void)
     DebugLog("Null descriptor        : %#p\n", &gdt[0]);
     DebugLog("Kernel code descriptor : %#p\n", &gdt[1]);
     DebugLog("Kernel data descriptor : %#p\n", &gdt[2]);
-    DebugLog("User data descriptor   : %#p\n", &gdt[3]);
+    DebugLog("User code descriptor   : %#p\n", &gdt[3]);
-    DebugLog("User code descriptor   : %#p\n", &gdt[4]);
+    DebugLog("User data descriptor   : %#p\n", &gdt[4]);
-    DebugLog("tss  : %#p\n", &gdt[5]);
+    DebugLog("Task-switch descriptor : %#p\n", &gdt[5]);
     DebugLog("ist1 : %#p\n", tss.ist1);
     DebugLog("ist2 : %#p\n", tss.ist2);
     DebugLog("ist3 : %#p\n", tss.ist3);

kaleid/kernel/sh/testcmds.c

@@ -331,7 +331,7 @@ error_t CmdSyscallTest(int argc, char **argv, char *cmdline)
 
 error_t CmdRing3Test(int argc, char **argv, char *cmdline)
 {
-    size_t size = 1*KB;
+    size_t size = 1*KPAGESIZE;
     void *entryPoint = (void*)USERSPACE;
     ulong flags = PRESENT | READWRITE | USERMODE;
 
@@ -348,7 +348,7 @@ error_t CmdRing3Test(int argc, char **argv, char *cmdline)
         return ENOMEM;
     }
     
-    size = 1*KB;
+    size = 1*KPAGESIZE;
     void *stackAddr = (void*)USERSPACE + 4*KPAGESIZE;
     flags = PRESENT | READWRITE | USERMODE;
 
@@ -365,15 +365,15 @@ error_t CmdRing3Test(int argc, char **argv, char *cmdline)
         return ENOMEM;
     }
     
-    KernLog("Entrypoint : %p, stack address : %p\n", entryPoint, stackAddr);
+    KernLog("Entrypoint : %p, stack address : %p\n", entryPoint, stackAddr+size);
     
     uchar *code = (uchar*)entryPoint;
     
-/*    *code = 0x90;       // nop*/
+    *code = 0x90;       // nop
-/*    *(code+1) = 0xEB;   // jmp*/
+    *(code+1) = 0xEB;   // jmp
-/*    *(code+2) = 0xFD;   //      short 0x0*/
+    *(code+2) = 0xFD;   //      short 0x0
 
-    KeJumpToUserspace(0, entryPoint, stackAddr);
+    KeJumpToUserspace(0, entryPoint, stackAddr+size);
 
     return EOK;
 }