From 4763ed4d45522b876c97e1f7f4b659d211f75571 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 13 Nov 2009 15:28:16 -0800 Subject: x86, mm: Clean up and simplify NX enablement The 32- and 64-bit code used very different mechanisms for enabling NX, but even the 32-bit code was enabling NX in head_32.S if it is available. Furthermore, we had a bewildering collection of tests for the available of NX. This patch: a) merges the 32-bit set_nx() and the 64-bit check_efer() function into a single x86_configure_nx() function. EFER control is left to the head code. b) eliminates the nx_enabled variable entirely. Things that need to test for NX enablement can verify __supported_pte_mask directly, and cpu_has_nx gives the supported status of NX. Signed-off-by: H. Peter Anvin Cc: Tejun Heo Cc: Brian Gerst Cc: Yinghai Lu Cc: Pekka Enberg Cc: Vegard Nossum Cc: Jeremy Fitzhardinge Cc: Chris Wright LKML-Reference: <1258154897-6770-5-git-send-email-hpa@zytor.com> Acked-by: Kees Cook --- arch/x86/mm/setup_nx.c | 43 ++++++------------------------------------- 1 file changed, 6 insertions(+), 37 deletions(-) (limited to 'arch/x86/mm/setup_nx.c') diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c index 513d8ed5d2e..355818b087b 100644 --- a/arch/x86/mm/setup_nx.c +++ b/arch/x86/mm/setup_nx.c @@ -3,10 +3,8 @@ #include #include +#include -int nx_enabled; - -#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE) static int disable_nx __cpuinitdata; /* @@ -22,48 +20,19 @@ static int __init noexec_setup(char *str) if (!str) return -EINVAL; if (!strncmp(str, "on", 2)) { - __supported_pte_mask |= _PAGE_NX; disable_nx = 0; } else if (!strncmp(str, "off", 3)) { disable_nx = 1; - __supported_pte_mask &= ~_PAGE_NX; } + x86_configure_nx(); return 0; } early_param("noexec", noexec_setup); -#endif - -#ifdef CONFIG_X86_PAE -void __init set_nx(void) -{ - unsigned int v[4], l, h; - - if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) { - cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]); - - if ((v[3] & (1 << 20)) && !disable_nx) { - rdmsr(MSR_EFER, l, h); - l |= EFER_NX; - wrmsr(MSR_EFER, l, h); - nx_enabled = 1; - __supported_pte_mask |= _PAGE_NX; - } - } -} -#else -void set_nx(void) -{ -} -#endif -#ifdef CONFIG_X86_64 -void __cpuinit check_efer(void) +void __cpuinit x86_configure_nx(void) { - unsigned long efer; - - rdmsrl(MSR_EFER, efer); - if (!(efer & EFER_NX) || disable_nx) + if (cpu_has_nx && !disable_nx) + __supported_pte_mask |= _PAGE_NX; + else __supported_pte_mask &= ~_PAGE_NX; } -#endif - -- cgit v1.2.3-70-g09d2 From 4b0f3b81eb33ef18283aa71440cccfede1753ae0 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 13 Nov 2009 15:28:17 -0800 Subject: x86, mm: Report state of NX protections during boot It is possible for x86_64 systems to lack the NX bit either due to the hardware lacking support or the BIOS having turned off the CPU capability, so NX status should be reported. Additionally, anyone booting NX-capable CPUs in 32bit mode without PAE will lack NX functionality, so this change provides feedback for that case as well. Signed-off-by: Kees Cook Signed-off-by: H. Peter Anvin LKML-Reference: <1258154897-6770-6-git-send-email-hpa@zytor.com> --- arch/x86/include/asm/proto.h | 1 + arch/x86/kernel/setup.c | 11 ++++++----- arch/x86/mm/init.c | 4 ---- arch/x86/mm/setup_nx.c | 22 ++++++++++++++++++++++ 4 files changed, 29 insertions(+), 9 deletions(-) (limited to 'arch/x86/mm/setup_nx.c') diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h index add7f18f17a..450c56bcd4f 100644 --- a/arch/x86/include/asm/proto.h +++ b/arch/x86/include/asm/proto.h @@ -17,6 +17,7 @@ extern void ia32_sysenter_target(void); extern void syscall32_cpu_init(void); extern void x86_configure_nx(void); +extern void x86_report_nx(void); extern int reboot_force; diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 23b7f46bf84..d2043a00abc 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -788,16 +788,17 @@ void __init setup_arch(char **cmdline_p) *cmdline_p = command_line; /* - * Must call this twice: Once just to detect whether hardware doesn't - * support NX (so that the early EHCI debug console setup can safely - * call set_fixmap(), and then again after parsing early parameters to - * honor the respective command line option. + * x86_configure_nx() is called before parse_early_param() to detect + * whether hardware doesn't support NX (so that the early EHCI debug + * console setup can safely call set_fixmap()). It may then be called + * again from within noexec_setup() during parsing early parameters + * to honor the respective command line option. */ x86_configure_nx(); parse_early_param(); - x86_configure_nx(); + x86_report_nx(); /* Must be before kernel pagetables are setup */ vmi_activate(); diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 27ec2c23fd4..d406c523901 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -146,10 +146,6 @@ unsigned long __init_refok init_memory_mapping(unsigned long start, use_gbpages = direct_gbpages; #endif - /* XXX: replace this with Kees' improved messages */ - if (__supported_pte_mask & _PAGE_NX) - printk(KERN_INFO "NX (Execute Disable) protection: active\n"); - /* Enable PSE if available */ if (cpu_has_pse) set_in_cr4(X86_CR4_PSE); diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c index 355818b087b..a3250aa3408 100644 --- a/arch/x86/mm/setup_nx.c +++ b/arch/x86/mm/setup_nx.c @@ -36,3 +36,25 @@ void __cpuinit x86_configure_nx(void) else __supported_pte_mask &= ~_PAGE_NX; } + +void __init x86_report_nx(void) +{ + if (!cpu_has_nx) { + printk(KERN_NOTICE "Notice: NX (Execute Disable) protection " + "missing in CPU or disabled in BIOS!\n"); + } else { +#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE) + if (disable_nx) { + printk(KERN_INFO "NX (Execute Disable) protection: " + "disabled by kernel command line option\n"); + } else { + printk(KERN_INFO "NX (Execute Disable) protection: " + "active\n"); + } +#else + /* 32bit non-PAE kernel, NX cannot be used */ + printk(KERN_NOTICE "Notice: NX (Execute Disable) protection " + "cannot be enabled: non-PAE kernel!\n"); +#endif + } +} -- cgit v1.2.3-70-g09d2