[S390] No execute support cleanup.

Simplify the signal_return function that checks for the two special
system calls sigreturn and rt_sigreturn. No need to do a page table
walk, a call to copy_from_user while disabled page faults will work
as well.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 21 insertions, 51 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 8bc35183db59..2b76a879a7b5 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -26,9 +26,9 @@
 #include <linux/module.h>
 #include <linux/hardirq.h>
 #include <linux/kprobes.h>
+#include <linux/uaccess.h>
 
 #include <asm/system.h>
-#include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/kdebug.h>
 #include <asm/s390_ext.h>
@@ -263,68 +263,38 @@ extern long sys_rt_sigreturn(struct pt_regs *regs);
 extern long sys32_sigreturn(struct pt_regs *regs);
 extern long sys32_rt_sigreturn(struct pt_regs *regs);
 
-static inline void do_sigreturn(struct mm_struct *mm, struct pt_regs *regs,
-                                int rt)
+static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
+                         unsigned long address, unsigned long error_code)
 {
+        u16 instruction;
+        int rc, compat;
+
+        pagefault_disable();
+        rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
+        pagefault_enable();
+        if (rc)
+                return -EFAULT;
+
         up_read(&mm->mmap_sem);
         clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
 #ifdef CONFIG_COMPAT
-        if (test_tsk_thread_flag(current, TIF_31BIT)) {
-                if (rt)
-                        sys32_rt_sigreturn(regs);
-                else
-                        sys32_sigreturn(regs);
-                return;
-        }
-#endif /* CONFIG_COMPAT */
-        if (rt)
-                sys_rt_sigreturn(regs);
+        compat = test_tsk_thread_flag(current, TIF_31BIT);
+        if (compat && instruction == 0x0a77)
+                sys32_sigreturn(regs);
+        else if (compat && instruction == 0x0aad)
+                sys32_rt_sigreturn(regs);
         else
+#endif
+        if (instruction == 0x0a77)
                 sys_sigreturn(regs);
-        return;
-}
-
-static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
-                         unsigned long address, unsigned long error_code)
-{
-        pgd_t *pgd;
-        pmd_t *pmd;
-        pte_t *pte;
-        u16 *instruction;
-        unsigned long pfn, uaddr = regs->psw.addr;
-
-        spin_lock(&mm->page_table_lock);
-        pgd = pgd_offset(mm, uaddr);
-        if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
-                goto out_fault;
-        pmd = pmd_offset(pgd, uaddr);
-        if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
-                goto out_fault;
-        pte = pte_offset_map(pmd_offset(pgd_offset(mm, uaddr), uaddr), uaddr);
-        if (!pte || !pte_present(*pte))
-                goto out_fault;
-        pfn = pte_pfn(*pte);
-        if (!pfn_valid(pfn))
-                goto out_fault;
-        spin_unlock(&mm->page_table_lock);
-
-        instruction = (u16 *) ((pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE-1)));
-        if (*instruction == 0x0a77)
-                do_sigreturn(mm, regs, 0);
-        else if (*instruction == 0x0aad)
-                do_sigreturn(mm, regs, 1);
+        else if (instruction == 0x0aad)
+                sys_rt_sigreturn(regs);
         else {
-                printk("- XXX - do_exception: task = %s, primary, NO EXEC "
-                       "-> SIGSEGV\n", current->comm);
-                up_read(&mm->mmap_sem);
                 current->thread.prot_addr = address;
                 current->thread.trap_no = error_code;
                 do_sigsegv(regs, error_code, SEGV_MAPERR, address);
         }
         return 0;
-out_fault:
-        spin_unlock(&mm->page_table_lock);
-        return -EFAULT;
 }
 #endif /* CONFIG_S390_EXEC_PROTECT */