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@@ -108,53 +108,40 @@ void bust_spinlocks(int yes)
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}
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/*
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- * Check which address space is addressed by the access
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- * register in S390_lowcore.exc_access_id.
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- * Returns 1 for user space and 0 for kernel space.
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+ * Returns the address space associated with the fault.
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+ * Returns 0 for kernel space, 1 for user space and
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+ * 2 for code execution in user space with noexec=on.
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*/
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-static int __check_access_register(struct pt_regs *regs, int error_code)
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-{
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- int areg = S390_lowcore.exc_access_id;
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-
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- if (areg == 0)
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- /* Access via access register 0 -> kernel address */
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- return 0;
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- save_access_regs(current->thread.acrs);
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- if (regs && areg < NUM_ACRS && current->thread.acrs[areg] <= 1)
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- /*
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- * access register contains 0 -> kernel address,
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- * access register contains 1 -> user space address
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- */
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- return current->thread.acrs[areg];
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-
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- /* Something unhealthy was done with the access registers... */
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- die("page fault via unknown access register", regs, error_code);
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- do_exit(SIGKILL);
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- return 0;
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-}
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-
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-/*
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- * Check which address space the address belongs to.
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- * May return 1 or 2 for user space and 0 for kernel space.
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- * Returns 2 for user space in primary addressing mode with
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- * CONFIG_S390_EXEC_PROTECT on and kernel parameter noexec=on.
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- */
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-static inline int check_user_space(struct pt_regs *regs, int error_code)
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+static inline int check_space(struct task_struct *tsk)
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{
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/*
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- * The lowest two bits of S390_lowcore.trans_exc_code indicate
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- * which paging table was used:
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- * 0: Primary Segment Table Descriptor
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- * 1: STD determined via access register
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- * 2: Secondary Segment Table Descriptor
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- * 3: Home Segment Table Descriptor
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+ * The lowest two bits of S390_lowcore.trans_exc_code
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+ * indicate which paging table was used.
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*/
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- int descriptor = S390_lowcore.trans_exc_code & 3;
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- if (unlikely(descriptor == 1))
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- return __check_access_register(regs, error_code);
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- if (descriptor == 2)
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- return current->thread.mm_segment.ar4;
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- return ((descriptor != 0) ^ (switch_amode)) << s390_noexec;
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+ int desc = S390_lowcore.trans_exc_code & 3;
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+
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+ if (desc == 3) /* Home Segment Table Descriptor */
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+ return switch_amode == 0;
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+ if (desc == 2) /* Secondary Segment Table Descriptor */
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+ return tsk->thread.mm_segment.ar4;
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+#ifdef CONFIG_S390_SWITCH_AMODE
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+ if (unlikely(desc == 1)) { /* STD determined via access register */
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+ /* %a0 always indicates primary space. */
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+ if (S390_lowcore.exc_access_id != 0) {
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+ save_access_regs(tsk->thread.acrs);
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+ /*
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+ * An alet of 0 indicates primary space.
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+ * An alet of 1 indicates secondary space.
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+ * Any other alet values generate an
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+ * alen-translation exception.
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+ */
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+ if (tsk->thread.acrs[S390_lowcore.exc_access_id])
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+ return tsk->thread.mm_segment.ar4;
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+ }
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+ }
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+#endif
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+ /* Primary Segment Table Descriptor */
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+ return switch_amode << s390_noexec;
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}
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/*
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@@ -265,16 +252,16 @@ out_fault:
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* 11 Page translation -> Not present (nullification)
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* 3b Region third trans. -> Not present (nullification)
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*/
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-static inline void __kprobes
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+static inline void
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do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
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{
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struct task_struct *tsk;
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struct mm_struct *mm;
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struct vm_area_struct * vma;
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unsigned long address;
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- int user_address;
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const struct exception_table_entry *fixup;
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- int si_code = SEGV_MAPERR;
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+ int si_code;
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+ int space;
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tsk = current;
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mm = tsk->mm;
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@@ -294,7 +281,7 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
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NULL pointer write access in kernel mode. */
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if (!(regs->psw.mask & PSW_MASK_PSTATE)) {
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address = 0;
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- user_address = 0;
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+ space = 0;
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goto no_context;
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}
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@@ -309,15 +296,15 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
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* the address
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*/
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address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
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- user_address = check_user_space(regs, error_code);
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+ space = check_space(tsk);
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/*
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* Verify that the fault happened in user space, that
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* we are not in an interrupt and that there is a
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* user context.
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*/
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- if (user_address == 0 || in_atomic() || !mm)
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- goto no_context;
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+ if (unlikely(space == 0 || in_atomic() || !mm))
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+ goto no_context;
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/*
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* When we get here, the fault happened in the current
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@@ -328,12 +315,13 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
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down_read(&mm->mmap_sem);
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- vma = find_vma(mm, address);
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- if (!vma)
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- goto bad_area;
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+ si_code = SEGV_MAPERR;
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+ vma = find_vma(mm, address);
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+ if (!vma)
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+ goto bad_area;
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#ifdef CONFIG_S390_EXEC_PROTECT
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- if (unlikely((user_address == 2) && !(vma->vm_flags & VM_EXEC)))
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+ if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC)))
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if (!signal_return(mm, regs, address, error_code))
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/*
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* signal_return() has done an up_read(&mm->mmap_sem)
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@@ -389,7 +377,7 @@ survive:
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* The instruction that caused the program check will
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* be repeated. Don't signal single step via SIGTRAP.
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*/
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- clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
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+ clear_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
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return;
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/*
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@@ -419,7 +407,7 @@ no_context:
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* Oops. The kernel tried to access some bad page. We'll have to
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* terminate things with extreme prejudice.
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*/
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- if (user_address == 0)
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+ if (space == 0)
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printk(KERN_ALERT "Unable to handle kernel pointer dereference"
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" at virtual kernel address %p\n", (void *)address);
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else
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@@ -462,13 +450,14 @@ do_sigbus:
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goto no_context;
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}
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-void do_protection_exception(struct pt_regs *regs, unsigned long error_code)
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+void __kprobes do_protection_exception(struct pt_regs *regs,
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+ unsigned long error_code)
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{
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regs->psw.addr -= (error_code >> 16);
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do_exception(regs, 4, 1);
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}
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-void do_dat_exception(struct pt_regs *regs, unsigned long error_code)
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+void __kprobes do_dat_exception(struct pt_regs *regs, unsigned long error_code)
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{
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do_exception(regs, error_code & 0xff, 0);
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}
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Gerald Schaefer