Merge pull request #1984 from ghaerr/tstack

[kernel] Use early temp stack to avoid irqit stack overruns on faults during startup

elks/arch/i86/boot/crt0.S

@@ -45,7 +45,7 @@ _start:
 
 	mov	%ds,%ax
 	mov	%ax,%ss		// SS=ES=DS
-	mov	$istack,%sp
+	mov	$tstack,%sp     // can't use kernel interrupt stack, must have temp stack
 
 	call	start_kernel	// fall through into breakpoint if returns
 
@@ -80,7 +80,7 @@ early_putchar:
 	.global _endbss
 	.extern	kernel_cs
 	.extern	kernel_ds
-	.extern	istack
+	.extern	tstack
 
 _endtext:
 	.word	0

elks/arch/i86/boot/setup.S

@@ -666,10 +666,10 @@ data_reloc:
 	jmp data_reloc
 3:
 
-	mov $'\r',%ax
-	call putc
-	mov $'\n',%ax
-	call putc
+//	mov $'\r',%ax
+//	call putc
+//	mov $'\n',%ax
+//	call putc
 
 // Load registers as kernel expects
 
@@ -688,7 +688,7 @@ data_reloc:
 	push %ax
 	push %cx
 
-	.hex4sp	%ss,"Done SS:"
+	.hex4sp	%ss,"\nDone SS:"
 	.hex4sp	%ds,"DS/ES:"
 	.hex4sp	%bx,".text size:"
 	.hex4sp	%di,".fartext size:"

elks/arch/i86/drivers/char/mem.c

@@ -240,7 +240,7 @@ int kmem_ioctl(struct inode *inode, struct file *file, int cmd, char *arg)
 	retword = kernel_ds;
 	break;
     case MEM_GETFARTEXT:
-        retword = (unsigned)((long)kernel_init >> 16);
+        retword = (unsigned)((long)buffer_init >> 16);
         break;
     case MEM_GETUSAGE:
 	mm_get_usage (&(mu.free_memory), &(mu.used_memory));

elks/arch/i86/kernel/Makefile

@@ -39,7 +39,8 @@ OBJS  = strace.o system.o irq.o irqtab.o process.o \
 		entry.o signal.o timer.o
 
 ifeq ($(CONFIG_ARCH_IBMPC), y)
-OBJS += irq-8259.o timer-8254.o divzero.o
+OBJS += irq-8259.o timer-8254.o
+#OBJS += divzero.o
 endif
 
 ifeq ($(CONFIG_ARCH_PC98), y)

elks/arch/i86/kernel/irq.c

@@ -124,9 +124,13 @@ void INITPROC irq_init(void)
     int_handler_add(IDX_SYSCALL, 0x80, _irqit);
 
 #ifdef CONFIG_ARCH_IBMPC
-    /* catch INT 0x00h divide by zero trap */
-    irq_action[IDX_DIVZERO] = div0_handler;
-    int_handler_add(IDX_DIVZERO, 0x00, _irqit);
+    /* catch INT 0 divide by zero/divide overflow hardware fault */
+    /*irq_action[IDX_DIVZERO] = div0_handler;
+      int_handler_add(IDX_DIVZERO, 0x00, _irqit);*/
+    /* install direct panic-only DIV fault handler until known that
+     * the _irqit version doesn't overwrite the stack
+     */
+    int_handler_add(IDX_DIVZERO, 0x00, div0_handler_panic);
 #endif
 
 #if defined(CONFIG_TIMER_INT0F) || defined(CONFIG_TIMER_INT1C)

elks/arch/i86/kernel/irqtab.S

@@ -392,10 +392,40 @@ idle_halt:
 	hlt
 	ret
 
+        .global div0_handler_panic
+// Divide Fault hander - just panic for now
+div0_handler_panic:
+        push    %ax                     // save regs, uses 4+4+10 bytes of current stack
+        push    %bx
+        push    %cx
+        push    %dx
+        push    %ds
+
+        // Recover kernel data segment
+        // Was pushed by the CALLF of the dynamic handler
+        mov     %sp,%bx
+        mov     %ss:12(%bx),%ds
+
+	mov	$dmsg,%ax
+	push	%ax
+	call    panic
+	pop	%ax
+1:	hlt
+	jmp	1b
+
+//      pop     %ds                     // restore regs
+//      pop     %dx
+//      pop     %cx
+//      pop     %bx
+//      pop     %ax
+//      add     $4,%sp          	// skip the trampoline lcall
+//      iret
+
 	.data
 	.global	_gint_count
 	.global	endistack
 	.global	istack
+	.global	tstack
 	.extern	current
 	.extern	previous
 
@@ -406,10 +436,14 @@ org_irq0:			// original BIOS IRQ 0 vector
 _gint_count:			// General interrupts count. Start with 1
 	.word	1		// because init_task() is in kernel mode
 #ifdef CHECK_SS
-pmsg:	.ascii "Running unknown code"
-	.byte	0
+pmsg:	.ascii "Running unknown code\0"
 #endif
+dmsg:	.ascii 	"DIVIDE FAULT\0"
+
 	.p2align 1
 endistack:
 	.skip ISTACK_BYTES,0	// interrupt stack
 istack:
+
+	.skip 256,0		// startup temp stack
+tstack:

elks/include/arch/irq.h

@@ -23,8 +23,9 @@ int request_irq(int,irq_handler,int hflag);
 int free_irq(int irq);
 
 /* irqtab.S */
-void int_vector_set (int vect, word_t proc, word_t seg);
 void _irqit (void);
+void int_vector_set (int vect, word_t proc, word_t seg);
+void div0_handler_panic(void);
 
 /* irq-8259.c, irq-8018x.c*/
 void initialize_irq(void);

elks/include/linuxmt/init.h

@@ -20,7 +20,6 @@ struct gendisk;
 struct drive_infot;
 
 /* kernel init routines*/
-extern void INITPROC kernel_init(void);
 extern int  INITPROC buffer_init(void);
 extern void INITPROC console_init(void);
 extern void INITPROC fs_init(void);

elks/init/main.c

@@ -89,8 +89,9 @@ static char * INITPROC option(char *s);
 #endif
 
 static void init_task(void);
-static void INITPROC kernel_banner(seg_t start, seg_t end, seg_t init, seg_t extra);
 static void INITPROC early_kernel_init(void);
+static void INITPROC kernel_init(void);
+static void INITPROC kernel_banner(seg_t start, seg_t end, seg_t init, seg_t extra);
 
 #if TIMER_TEST
 void testloop(unsigned timer)
@@ -118,10 +119,12 @@ void testloop(unsigned timer)
 /* this procedure called using temp stack then switched, no local vars allowed */
 void start_kernel(void)
 {
+    printk("START\n");
     early_kernel_init();        /* read bootopts using kernel interrupt stack */
     task = heap_alloc(max_tasks * sizeof(struct task_struct),
         HEAP_TAG_TASK|HEAP_TAG_CLEAR);
     if (!task) panic("No task mem");
+    sched_init();               /* set us (the current stack) to be idle task #0*/
     setsp(&task->t_regs.ax);    /* change to idle task stack */
     kernel_init();              /* continue init running on idle task stack */
 
@@ -168,17 +171,14 @@ static void INITPROC early_kernel_init(void)
 #endif
 }
 
-void INITPROC kernel_init(void)
+static void INITPROC kernel_init(void)
 {
-    /* set us (the current stack) to be idle task #0*/
-    sched_init();
-    irq_init();
+    irq_init();                     /* installs timer and div fault handlers */
 
     /* set console from /bootopts console= or 0=default*/
     set_console(boot_console);
 
-    /* init direct, bios or headless console*/
-    console_init();
+    console_init();                 /* init direct, bios or headless console*/
 
 #ifdef CONFIG_CHAR_DEV_RS
     serial_init();