bitkeeper revision 1.1159.170.31 (419a3a86bSLSt5jRubDsLFc4VXWrkQ)

Sanitise failsafe callback. The safe pf handler stuff was madness.
If it turns out to be needed, there must be a better way.

linux-2.4.27-xen-sparse/arch/xen/kernel/entry.S

@@ -369,28 +369,19 @@ critical_fixup_table:
 
 # Hypervisor uses this for application faults while it executes.
 ENTRY(failsafe_callback)
-        pushal
-        call SYMBOL_NAME(install_safe_pf_handler)
-        movl 32(%esp),%ebx
-1:      movl %ebx,%ds
-        movl 36(%esp),%ebx
-2:      movl %ebx,%es
-        movl 40(%esp),%ebx
-3:      movl %ebx,%fs
-        movl 44(%esp),%ebx
-4:      movl %ebx,%gs
-        call SYMBOL_NAME(install_normal_pf_handler)
-        popal
-        addl $16,%esp
+1:      popl %ds
+2:      popl %es
+3:      popl %fs
+4:      popl %gs
 5:      iret
 .section .fixup,"ax";	\
-6:	xorl %ebx,%ebx;	\
+6:	movl $0,(%esp);	\
 	jmp 1b;		\
-7:	xorl %ebx,%ebx;	\
+7:	movl $0,(%esp);	\
 	jmp 2b;		\
-8:	xorl %ebx,%ebx;	\
+8:	movl $0,(%esp);	\
 	jmp 3b;		\
-9:	xorl %ebx,%ebx;	\
+9:	movl $0,(%esp);	\
 	jmp 4b;		\
 10:	pushl %ss;	\
 	popl %ds;	\
@@ -511,7 +502,6 @@ ENTRY(_name1)                                                            \
 	addl $12,%esp                                                  ; \
 	jmp ret_from_exception                                         ;
 PAGE_FAULT_STUB(page_fault, do_page_fault)
-PAGE_FAULT_STUB(safe_page_fault, do_safe_page_fault)
 
 ENTRY(machine_check)
 	pushl $0

linux-2.4.27-xen-sparse/arch/xen/kernel/traps.c

@@ -59,7 +59,6 @@ asmlinkage void segment_not_present(void);
 asmlinkage void stack_segment(void);
 asmlinkage void general_protection(void);
 asmlinkage void page_fault(void);
-asmlinkage void safe_page_fault(void);
 asmlinkage void coprocessor_error(void);
 asmlinkage void simd_coprocessor_error(void);
 asmlinkage void alignment_check(void);
@@ -627,65 +626,3 @@ void __init trap_init(void)
 
     cpu_init();
 }
-
-
-/*
- * install_safe_pf_handler / install_normal_pf_handler:
- * 
- * These are used within the failsafe_callback handler in entry.S to avoid
- * taking a full page fault when reloading FS and GS. This is because FS and 
- * GS could be invalid at pretty much any point while Xenolinux executes (we 
- * don't set them to safe values on entry to the kernel). At *any* point Xen 
- * may be entered due to a hardware interrupt --- on exit from Xen an invalid 
- * FS/GS will cause our failsafe_callback to be executed. This could occur, 
- * for example, while the mmu_update_queue is in an inconsistent state. This
- * is disastrous because the normal page-fault handler touches the update
- * queue!
- * 
- * Fortunately, within the failsafe handler it is safe to force DS/ES/FS/GS
- * to zero if they cannot be reloaded -- at this point executing a normal
- * page fault would not change this effect. The safe page-fault handler
- * ensures this end result (blow away the selector value) without the dangers
- * of the normal page-fault handler.
- * 
- * NB. Perhaps this can all go away after we have implemented writable
- * page tables. :-)
- */
-
-asmlinkage void do_safe_page_fault(struct pt_regs *regs, 
-                                   unsigned long error_code,
-                                   unsigned long address)
-{
-    unsigned long fixup;
-
-    if ( (fixup = search_exception_table(regs->eip)) != 0 )
-    {
-        regs->eip = fixup;
-        return;
-    }
-
-    die("Unhandleable 'safe' page fault!", regs, error_code);
-}
-
-unsigned long install_safe_pf_handler(void)
-{
-    static trap_info_t safe_pf[] = { 
-        { 14, 0, __KERNEL_CS, (unsigned long)safe_page_fault },
-        {  0, 0,           0, 0                              }
-    };
-    unsigned long flags;
-    local_irq_save(flags);
-    HYPERVISOR_set_trap_table(safe_pf);
-    return flags; /* This is returned in %%eax */
-}
-
-__attribute__((regparm(3))) /* This function take its arg in %%eax */
-void install_normal_pf_handler(unsigned long flags)
-{
-    static trap_info_t normal_pf[] = { 
-        { 14, 0, __KERNEL_CS, (unsigned long)page_fault },
-        {  0, 0,           0, 0                         }
-    };
-    HYPERVISOR_set_trap_table(normal_pf);
-    local_irq_restore(flags);
-}

linux-2.6.9-xen-sparse/arch/xen/i386/kernel/entry.S

@@ -510,28 +510,19 @@ critical_fixup_table:
 
 # Hypervisor uses this for application faults while it executes.
 ENTRY(failsafe_callback)
-	pushal
-	call install_safe_pf_handler
-	movl 32(%esp),%ebx
-1:	movl %ebx,%ds
-	movl 36(%esp),%ebx
-2:	movl %ebx,%es
-	movl 40(%esp),%ebx
-3:	movl %ebx,%fs
-	movl 44(%esp),%ebx
-4:	movl %ebx,%gs
-	call install_normal_pf_handler
-	popal
-	addl $16,%esp
+1:      popl %ds
+2:      popl %es
+3:      popl %fs
+4:      popl %gs
 5:	iret
 .section .fixup,"ax";	\
-6:	xorl %ebx,%ebx;	\
+6:	movl $0,(%esp);	\
 	jmp 1b;		\
-7:	xorl %ebx,%ebx;	\
+7:	movl $0,(%esp);	\
 	jmp 2b;		\
-8:	xorl %ebx,%ebx;	\
+8:	movl $0,(%esp);	\
 	jmp 3b;		\
-9:	xorl %ebx,%ebx;	\
+9:	movl $0,(%esp);	\
 	jmp 4b;		\
 10:	pushl %ss;	\
 	popl %ds;	\
@@ -726,7 +717,6 @@ ENTRY(_name1)								  \
 	addl $12,%esp							; \
 	jmp ret_from_exception						;
 PAGE_FAULT_STUB(page_fault, do_page_fault)
-PAGE_FAULT_STUB(safe_page_fault, do_safe_page_fault)
 
 #ifdef CONFIG_X86_MCE
 ENTRY(machine_check)

linux-2.6.9-xen-sparse/arch/xen/i386/kernel/traps.c

@@ -60,8 +60,6 @@ asmlinkage int system_call(void);
 asmlinkage void lcall7(void);
 asmlinkage void lcall27(void);
 
-asmlinkage void safe_page_fault(void);
-
 /* Do we ignore FPU interrupts ? */
 char ignore_fpu_irq = 0;
 
@@ -1072,58 +1070,3 @@ void __init trap_init(void)
 	 */
 	cpu_init();
 }
-
-
-/*
- * install_safe_pf_handler / install_normal_pf_handler:
- * 
- * These are used within the failsafe_callback handler in entry.S to avoid
- * taking a full page fault when reloading FS and GS. This is because FS and 
- * GS could be invalid at pretty much any point while Xen Linux executes (we 
- * don't set them to safe values on entry to the kernel). At *any* point Xen 
- * may be entered due to a hardware interrupt --- on exit from Xen an invalid 
- * FS/GS will cause our failsafe_callback to be executed. This could occur, 
- * for example, while the mmmu_update_queue is in an inconsistent state. This
- * is disastrous because the normal page-fault handler touches the update
- * queue!
- * 
- * Fortunately, within the failsafe handler it is safe to force DS/ES/FS/GS
- * to zero if they cannot be reloaded -- at this point executing a normal
- * page fault would not change this effect. The safe page-fault handler
- * ensures this end result (blow away the selector value) without the dangers
- * of the normal page-fault handler.
- * 
- * NB. Perhaps this can all go away after we have implemented writable
- * page tables. :-)
- */
-
-asmlinkage void do_safe_page_fault(struct pt_regs *regs, 
-                                   unsigned long error_code,
-                                   unsigned long address)
-{
-	if (!fixup_exception(regs))
-		die("Unhandleable 'safe' page fault!", regs, error_code);
-}
-
-unsigned long install_safe_pf_handler(void)
-{
-	static trap_info_t safe_pf[] = { 
-		{ 14, 0, __KERNEL_CS, (unsigned long)safe_page_fault },
-		{  0, 0,           0, 0                              }
-	};
-	unsigned long flags;
-	local_irq_save(flags);
-	HYPERVISOR_set_trap_table(safe_pf);
-	return flags; /* This is returned in %%eax */
-}
-
-__attribute__((regparm(3))) /* This function take its arg in %%eax */
-void install_normal_pf_handler(unsigned long flags)
-{
-	static trap_info_t normal_pf[] = { 
-		{ 14, 0, __KERNEL_CS, (unsigned long)page_fault },
-		{  0, 0,           0, 0                         }
-	};
-	HYPERVISOR_set_trap_table(normal_pf);
-	local_irq_restore(flags);
-}