parisc: provide macro to create exception table entries

Provide a macro ASM_EXCEPTIONTABLE_ENTRY() to create exception table
entries and convert all open-coded places to use that macro.

This patch is a first step toward creating a exception table which only
holds 32bit pointers even on a 64bit kernel. That way in my own kernel
I was able to reduce the in-kernel exception table from 44kB to 22kB.

Signed-off-by: Helge Deller <deller@gmx.de>

5 files changed, 27 insertions, 14 deletions

diff --git a/arch/parisc/include/asm/assembly.h b/arch/parisc/include/asm/assembly.h
index 0da848232344..b3069fd83468 100644
--- a/arch/parisc/include/asm/assembly.h
+++ b/arch/parisc/include/asm/assembly.h
@@ -515,5 +515,17 @@
         nop     /* 7 */
         .endm
 
+        /*
+         * ASM_EXCEPTIONTABLE_ENTRY
+         *
+         * Creates an exception table entry.
+         * Do not convert to a assembler macro. This won't work.
+         */
+#define ASM_EXCEPTIONTABLE_ENTRY(fault_addr, except_addr)       \
+        .section __ex_table,"aw"                        !       \
+        ASM_ULONG_INSN  fault_addr, except_addr         !       \
+        .previous
+
+
 #endif /* __ASSEMBLY__ */
 #endif
diff --git a/arch/parisc/include/asm/uaccess.h b/arch/parisc/include/asm/uaccess.h
index e0a82358517e..4006964d8e12 100644
--- a/arch/parisc/include/asm/uaccess.h
+++ b/arch/parisc/include/asm/uaccess.h
@@ -59,12 +59,13 @@ static inline long access_ok(int type, const void __user * addr,
 /*
  * The exception table contains two values: the first is an address
  * for an instruction that is allowed to fault, and the second is
- * the address to the fixup routine. 
+ * the address to the fixup routine. Even on a 64bit kernel we could
+ * use a 32bit (unsigned int) address here.
  */
 
 struct exception_table_entry {
-        unsigned long insn;  /* address of insn that is allowed to fault.   */
-        long fixup;          /* fixup routine */
+        unsigned long insn;     /* address of insn that is allowed to fault. */
+        unsigned long fixup;    /* fixup routine */
 };
 
 #define ASM_EXCEPTIONTABLE_ENTRY( fault_addr, except_addr )\
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index e767ab733e32..a63bb179f79a 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -649,10 +649,8 @@ cas_action:
         /* Two exception table entries, one for the load,
            the other for the store. Either return -EFAULT.
            Each of the entries must be relocated. */
-        .section __ex_table,"aw"
-        ASM_ULONG_INSN (1b - linux_gateway_page), (3b - linux_gateway_page)
-        ASM_ULONG_INSN (2b - linux_gateway_page), (3b - linux_gateway_page)
-        .previous
+        ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page)
+        ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page)
 
 
         /* Make sure nothing else is placed on this page */
diff --git a/arch/parisc/lib/lusercopy.S b/arch/parisc/lib/lusercopy.S
index 6f2d9355efe2..a512f07d4feb 100644
--- a/arch/parisc/lib/lusercopy.S
+++ b/arch/parisc/lib/lusercopy.S
@@ -88,9 +88,7 @@ ENDPROC(lclear_user)
         ldo        1(%r25),%r25
         .previous
 
-        .section __ex_table,"aw"
-        ASM_ULONG_INSN 1b,2b
-        .previous
+        ASM_EXCEPTIONTABLE_ENTRY(1b,2b)
 
         .procend
 
@@ -129,10 +127,8 @@ ENDPROC(lstrnlen_user)
         copy        %r24,%r26    /* reset r26 so 0 is returned on fault */
         .previous
 
-        .section __ex_table,"aw"
-        ASM_ULONG_INSN 1b,3b
-        ASM_ULONG_INSN 2b,3b
-        .previous
+        ASM_EXCEPTIONTABLE_ENTRY(1b,3b)
+        ASM_EXCEPTIONTABLE_ENTRY(2b,3b)
 
         .procend
 
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 0293588d5b8c..df0d32971cdf 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -142,6 +142,12 @@ int fixup_exception(struct pt_regs *regs)
 {
         const struct exception_table_entry *fix;
 
+        /* If we only stored 32bit addresses in the exception table we can drop
+         * out if we faulted on a 64bit address. */
+        if ((sizeof(regs->iaoq[0]) > sizeof(fix->insn))
+                && (regs->iaoq[0] >> 32))
+                        return 0;
+
         fix = search_exception_tables(regs->iaoq[0]);
         if (fix) {
                 struct exception_data *d;