Revert most of "x86: Fix alternatives and kprobes to remap write-prot…

…ected kernel text" This reverts most of commit 19d36cc. 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 <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
ambv · Jul 26, 2007 · 602033e · 602033e
1 parent 07d4e9a
commit 602033e
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Showing 3 changed files with 23 additions and 15 deletions.
diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c
@@ -430,22 +430,12 @@ void __init alternative_instructions(void)
  * And on the local CPU you need to be protected again NMI or MCE handlers
  * seeing an inconsistent instruction while you patch.
  */
-void __kprobes text_poke(void *oaddr, unsigned char *opcode, int len)
+void __kprobes text_poke(void *addr, unsigned char *opcode, int len)
 {
-        u8 *addr = oaddr;
-	if (!pte_write(*lookup_address((unsigned long)addr))) {
-		struct page *p[2] = { virt_to_page(addr), virt_to_page(addr+PAGE_SIZE) };
-		addr = vmap(p, 2, VM_MAP, PAGE_KERNEL);
-		if (!addr)
-			return;
-		addr += ((unsigned long)oaddr) % PAGE_SIZE;
-	}
 	memcpy(addr, opcode, len);
 	sync_core();
 	/* Not strictly needed, but can speed CPU recovery up. Ignore cross cacheline
 	   case. */
 	if (cpu_has_clflush)
-		asm("clflush (%0) " :: "r" (oaddr) : "memory");
-	if (addr != oaddr)
-		vunmap(addr);
+		asm("clflush (%0) " :: "r" (addr) : "memory");
 }
diff --git 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),

diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
@@ -600,6 +600,16 @@ void mark_rodata_ro(void)
 {
 	unsigned long start = (unsigned long)_stext, end;
 
+#ifdef CONFIG_HOTPLUG_CPU
+	/* It must still be possible to apply SMP alternatives. */
+	if (num_possible_cpus() > 1)
+		start = (unsigned long)_etext;
+#endif
+
+#ifdef CONFIG_KPROBES
+	start = (unsigned long)__start_rodata;
+#endif
+
 	end = (unsigned long)__end_rodata;
 	start = (start + PAGE_SIZE - 1) & PAGE_MASK;
 	end &= PAGE_MASK;