parisc: Fix and improve kernel stack unwinding

This patchset fixes and improves stack unwinding a lot:
1. Show backward stack traces with up to 30 callsites
2. Add callinfo to ENTRY_CFI() such that every assembler function will get an
   entry in the unwind table
3. Use constants instead of numbers in call_on_stack()
4. Do not depend on CONFIG_KALLSYMS to generate backtraces.
5. Speed up backtrace generation

Make sure you have this patch to GNU as installed:
https://sourceware.org/ml/binutils/2018-07/msg00474.html
Without this patch, unwind info in the kernel is often wrong for various
functions.

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

arch/parisc/lib/lusercopy.S

@@ -64,9 +64,6 @@
 	 */
 
 ENTRY_CFI(lclear_user)
-	.proc
-	.callinfo NO_CALLS
-	.entry
 	comib,=,n   0,%r25,$lclu_done
 	get_sr
 $lclu_loop:
@@ -81,13 +78,9 @@ $lclu_done:
 	ldo         1(%r25),%r25
 
 	ASM_EXCEPTIONTABLE_ENTRY(1b,2b)
-
-	.exit
 ENDPROC_CFI(lclear_user)
 
 
-	.procend
-
 	/*
 	 * long lstrnlen_user(char *s, long n)
 	 *
@@ -97,9 +90,6 @@ ENDPROC_CFI(lclear_user)
 	 */
 
 ENTRY_CFI(lstrnlen_user)
-	.proc
-	.callinfo NO_CALLS
-	.entry
 	comib,=     0,%r25,$lslen_nzero
 	copy	    %r26,%r24
 	get_sr
@@ -111,7 +101,6 @@ $lslen_loop:
 $lslen_done:
 	bv          %r0(%r2)
 	sub	    %r26,%r24,%r28
-	.exit
 
 $lslen_nzero:
 	b           $lslen_done
@@ -125,9 +114,6 @@ $lslen_nzero:
 
 ENDPROC_CFI(lstrnlen_user)
 
-	.procend
-
-
 
 /*
  * unsigned long pa_memcpy(void *dstp, const void *srcp, unsigned long len)
@@ -186,10 +172,6 @@ ENDPROC_CFI(lstrnlen_user)
 	save_len = r31
 
 ENTRY_CFI(pa_memcpy)
-	.proc
-	.callinfo NO_CALLS
-	.entry
-
 	/* Last destination address */
 	add	dst,len,end
 
@@ -439,9 +421,6 @@ ENTRY_CFI(pa_memcpy)
 	b	.Lcopy_done
 10:	stw,ma	t1,4(dstspc,dst)
 	ASM_EXCEPTIONTABLE_ENTRY(10b,.Lcopy_done)
-
-	.exit
 ENDPROC_CFI(pa_memcpy)
-	.procend
 
 	.end