From 8a50e5135af0c243e117e94e27feb8d149c879b4 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 13 Nov 2009 15:28:13 -0800 Subject: [PATCH] x86-32: Use symbolic constants, safer CPUID when enabling EFER.NX Use symbolic constants rather than hard-coded values when setting EFER.NX in head_32.S, and do a more rigorous test for the validity of the response when probing for the extended CPUID range. Signed-off-by: H. Peter Anvin LKML-Reference: <1258154897-6770-2-git-send-email-hpa@zytor.com> Acked-by: Kees Cook --- arch/x86/kernel/head_32.S | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 050c278481b..7fd318bac59 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -18,6 +18,8 @@ #include #include #include +#include +#include #include /* Physical address */ @@ -297,25 +299,27 @@ ENTRY(startup_32_smp) orl %edx,%eax movl %eax,%cr4 - btl $5, %eax # check if PAE is enabled - jnc 6f + testb $X86_CR4_PAE, %al # check if PAE is enabled + jz 6f /* Check if extended functions are implemented */ movl $0x80000000, %eax cpuid - cmpl $0x80000000, %eax - jbe 6f + /* Value must be in the range 0x80000001 to 0x8000ffff */ + subl $0x80000001, %eax + cmpl $(0x8000ffff-0x80000001), %eax + ja 6f mov $0x80000001, %eax cpuid /* Execute Disable bit supported? */ - btl $20, %edx + btl $(X86_FEATURE_NX & 31), %edx jnc 6f /* Setup EFER (Extended Feature Enable Register) */ - movl $0xc0000080, %ecx + movl $MSR_EFER, %ecx rdmsr - btsl $11, %eax + btsl $_EFER_NX, %eax /* Make changes effective */ wrmsr -- 2.46.0