Revert most of "x86: Fix alternatives and kprobes to remap write-protected kernel text"

This reverts most of commit 19d36ccdc34f5ed444f8a6af0cbfdb6790eb1177.

The way to DEBUG_RODATA interactions with KPROBES and CPU hotplug is to
just not mark the text as being write-protected in the first place.
Both of those facilities depend on rewriting instructions.

Having "helpful" debug facilities that just cause more problem is not
being helpful.  It just adds complexity and bugs. Not worth it.

Reported-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index 1b1a1e66d099..4c4809f13cb1 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -800,9 +800,17 @@ void mark_rodata_ro(void)
         unsigned long start = PFN_ALIGN(_text);
         unsigned long size = PFN_ALIGN(_etext) - start;
 
-        change_page_attr(virt_to_page(start),
-                         size >> PAGE_SHIFT, PAGE_KERNEL_RX);
-        printk("Write protecting the kernel text: %luk\n", size >> 10);
+#ifndef CONFIG_KPROBES
+#ifdef CONFIG_HOTPLUG_CPU
+        /* It must still be possible to apply SMP alternatives. */
+        if (num_possible_cpus() <= 1)
+#endif
+        {
+                change_page_attr(virt_to_page(start),
+                                 size >> PAGE_SHIFT, PAGE_KERNEL_RX);
+                printk("Write protecting the kernel text: %luk\n", size >> 10);
+        }
+#endif
         start += size;
         size = (unsigned long)__end_rodata - start;
         change_page_attr(virt_to_page(start),