[S390] dynamic page tables.

Add support for different number of page table levels dependent
on the highest address used for a process. This will cause a 31 bit
process to use a two level page table instead of the four level page
table that is the default after the pud has been introduced. Likewise
a normal 64 bit process will use three levels instead of four. Only
if a process runs out of the 4 tera bytes which can be addressed with
a three level page table the fourth level is dynamically added. Then
the process can use up to 8 peta byte.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/binfmt_elf32.c

@@ -134,6 +134,7 @@ static inline int dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
 }
 
 #include <asm/processor.h>
+#include <asm/pgalloc.h>
 #include <linux/module.h>
 #include <linux/elfcore.h>
 #include <linux/binfmts.h>
@@ -183,6 +184,16 @@ struct elf_prpsinfo32
 #undef start_thread
 #define start_thread                    start_thread31 
 
+static inline void start_thread31(struct pt_regs *regs, unsigned long new_psw,
+				  unsigned long new_stackp)
+{
+	set_fs(USER_DS);
+	regs->psw.mask	= psw_user32_bits;
+	regs->psw.addr	= new_psw;
+	regs->gprs[15]	= new_stackp;
+	crst_table_downgrade(current->mm, 1UL << 31);
+}
+
 MODULE_DESCRIPTION("Binary format loader for compatibility with 32bit Linux for S390 binaries,"
                    " Copyright 2000 IBM Corporation"); 
 MODULE_AUTHOR("Gerhard Tonn <ton@de.ibm.com>");

arch/s390/kernel/traps.c

@@ -60,6 +60,7 @@ int sysctl_userprocess_debug = 0;
 extern pgm_check_handler_t do_protection_exception;
 extern pgm_check_handler_t do_dat_exception;
 extern pgm_check_handler_t do_monitor_call;
+extern pgm_check_handler_t do_asce_exception;
 
 #define stack_pointer ({ void **sp; asm("la %0,0(15)" : "=&d" (sp)); sp; })
 
@@ -730,7 +731,7 @@ void __init trap_init(void)
         pgm_check_table[0x12] = &translation_exception;
         pgm_check_table[0x13] = &special_op_exception;
 #ifdef CONFIG_64BIT
-        pgm_check_table[0x38] = &do_dat_exception;
+	pgm_check_table[0x38] = &do_asce_exception;
 	pgm_check_table[0x39] = &do_dat_exception;
 	pgm_check_table[0x3A] = &do_dat_exception;
         pgm_check_table[0x3B] = &do_dat_exception;