From 602033ed5907a59ce86f709082a35be047743a86 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 26 Jul 2007 12:07:21 -0700 Subject: [PATCH] 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 Cc: Andi Kleen Cc: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/alternative.c | 14 ++------------ arch/i386/mm/init.c | 14 +++++++++++--- arch/x86_64/mm/init.c | 10 ++++++++++ 3 files changed, 23 insertions(+), 15 deletions(-) diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c index c3750c2c41..c85598acb8 100644 --- 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 index 1b1a1e66d0..4c4809f13c 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), diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c index 38f5d63680..458893b376 100644 --- 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; -- 2.39.5