Merge branch 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perparatory x86 kasrl changes from Ingo Molnar:
 "This contains changes from the ongoing KASLR work, by Kees Cook.

  The main changes are the use of a read-only IDT on x86 (which
  decouples the userspace visible virtual IDT address from the physical
  address), and a rework of ELF relocation support, in preparation of
  random, boot-time kernel image relocation."

* 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, relocs: Refactor the relocs tool to merge 32- and 64-bit ELF
  x86, relocs: Build separate 32/64-bit tools
  x86, relocs: Add 64-bit ELF support to relocs tool
  x86, relocs: Consolidate processing logic
  x86, relocs: Generalize ELF structure names
  x86: Use a read-only IDT alias on all CPUs

2 files changed, 10 insertions, 17 deletions

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index a942b7c2cce..9b0c441c03f 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -176,20 +176,6 @@ int __cpuinit ppro_with_ram_bug(void)
 	return 0;
 }
 
-#ifdef CONFIG_X86_F00F_BUG
-static void __cpuinit trap_init_f00f_bug(void)
-{
-	__set_fixmap(FIX_F00F_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);
-
-	/*
-	 * Update the IDT descriptor and reload the IDT so that
-	 * it uses the read-only mapped virtual address.
-	 */
-	idt_descr.address = fix_to_virt(FIX_F00F_IDT);
-	load_idt(&idt_descr);
-}
-#endif
-
 static void __cpuinit intel_smp_check(struct cpuinfo_x86 *c)
 {
 	/* calling is from identify_secondary_cpu() ? */
@@ -218,8 +204,7 @@ static void __cpuinit intel_workarounds(struct cpuinfo_x86 *c)
 	/*
 	 * All current models of Pentium and Pentium with MMX technology CPUs
 	 * have the F0 0F bug, which lets nonprivileged users lock up the
-	 * system.
-	 * Note that the workaround only should be initialized once...
+	 * system. Announce that the fault handler will be checking for it.
 	 */
 	clear_cpu_bug(c, X86_BUG_F00F);
 	if (!paravirt_enabled() && c->x86 == 5) {
@@ -227,7 +212,6 @@ static void __cpuinit intel_workarounds(struct cpuinfo_x86 *c)
 
 		set_cpu_bug(c, X86_BUG_F00F);
 		if (!f00f_workaround_enabled) {
-			trap_init_f00f_bug();
 			printk(KERN_NOTICE "Intel Pentium with F0 0F bug - workaround enabled.\n");
 			f00f_workaround_enabled = 1;
 		}
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index ff6d2271cbe..772e2a846de 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -56,6 +56,7 @@
 #include <asm/i387.h>
 #include <asm/fpu-internal.h>
 #include <asm/mce.h>
+#include <asm/fixmap.h>
 #include <asm/mach_traps.h>
 
 #ifdef CONFIG_X86_64
@@ -769,6 +770,14 @@ void __init trap_init(void)
 #endif
 
 	/*
+	 * Set the IDT descriptor to a fixed read-only location, so that the
+	 * "sidt" instruction will not leak the location of the kernel, and
+	 * to defend the IDT against arbitrary memory write vulnerabilities.
+	 * It will be reloaded in cpu_init() */
+	__set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);
+	idt_descr.address = fix_to_virt(FIX_RO_IDT);
+
+	/*
 	 * Should be a barrier for any external CPU state:
 	 */
 	cpu_init();