parisc: Fix initial page table creation for boot

The KERNEL_INITIAL_ORDER value defines the initial size (usually 32 or
64 MB) of the page table during bootup. Up until now the whole area was
initialized with PTE entries, but there was no check if we filled too
many entries.  Change the code to fill up with so many entries that the
"_end" symbol can be reached by the kernel, but not more entries than
actually fit into the initial PTE tables.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v6.0+

Author: hdeller

arch/parisc/kernel/head.S

@@ -56,6 +56,7 @@ ENTRY(parisc_kernel_start)
 
 	.import __bss_start,data
 	.import __bss_stop,data
+	.import __end,data
 
 	load32		PA(__bss_start),%r3
 	load32		PA(__bss_stop),%r4
@@ -149,7 +150,11 @@ $cpu_ok:
 	 * everything ... it will get remapped correctly later */
 	ldo		0+_PAGE_KERNEL_RWX(%r0),%r3 /* Hardwired 0 phys addr start */
 	load32		(1<<(KERNEL_INITIAL_ORDER-PAGE_SHIFT)),%r11 /* PFN count */
-	load32		PA(pg0),%r1
+	load32		PA(_end),%r1
+	SHRREG		%r1,PAGE_SHIFT,%r1  /* %r1 is PFN count for _end symbol */
+	cmpb,<<,n	%r11,%r1,1f
+	copy		%r1,%r11	/* %r1 PFN count smaller than %r11 */
+1:	load32		PA(pg0),%r1
 
 $pgt_fill_loop:
 	STREGM          %r3,ASM_PTE_ENTRY_SIZE(%r1)