[PATCH 2/6] x86: kaslr: move CPU flags out of cpucheck

Kees Cook
2013-04-25T21:55:36Z

Refactor the CPU flags handling out of the cpucheck routines so that
they can be reused by the future ASLR routines (in order to detect CPU
features like RDRAND and RDTSC).

Since has_eflag() and has_fpu() are 32-bit only, short-circuit the
routines on 64-bit when they are built without -m32. This also refactors
the calls to cpuid to make them PIC-safe on 32-bit.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/boot/Makefile | 2 +-
arch/x86/boot/boot.h | 10 +---
arch/x86/boot/compressed/Makefile | 2 +-
arch/x86/boot/compressed/cpuflags.c | 12 ++++
arch/x86/boot/cpucheck.c | 86 ---------------------------
arch/x86/boot/cpuflags.c | 109 +++++++++++++++++++++++++++++++++++
arch/x86/boot/cpuflags.h | 19 ++++++
7 files changed, 143 insertions(+), 97 deletions(-)
create mode 100644 arch/x86/boot/compressed/cpuflags.c
create mode 100644 arch/x86/boot/cpuflags.c
create mode 100644 arch/x86/boot/cpuflags.h

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index 379814b..0da2e37 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -20,7 +20,7 @@ targets := vmlinux.bin setup.bin setup.elf bzImage
targets += fdimage fdimage144 fdimage288 image.iso mtools.conf
subdir- := compressed

-setup-y += a20.o bioscall.o cmdline.o copy.o cpu.o cpucheck.o
+setup-y += a20.o bioscall.o cmdline.o copy.o cpu.o cpuflags.o cpucheck.o
setup-y += early_serial_console.o edd.o header.o main.o mca.o memory.o
setup-y += pm.o pmjump.o printf.o regs.o string.o tty.o video.o
setup-y += video-mode.o version.o
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 5b75319..59c5ada 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -26,9 +26,8 @@
#include <asm/boot.h>
#include <asm/setup.h>
#include "bitops.h"
-#include <asm/cpufeature.h>
-#include <asm/processor-flags.h>
#include "ctype.h"
+#include "cpuflags.h"

/* Useful macros */
#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
@@ -307,14 +306,7 @@ static inline int cmdline_find_option_bool(const char *option)
return __cmdline_find_option_bool(cmd_line_ptr, option);
}

-
/* cpu.c, cpucheck.c */
-struct cpu_features {
- int level; /* Family, or 64 for x86-64 */
- int model;
- u32 flags[NCAPINTS];
-};
-extern struct cpu_features cpu;
int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr);
int validate_cpu(void);

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 5ef205c..d854390 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -26,7 +26,7 @@ HOST_EXTRACFLAGS += -I$(srctree)/tools/include

VMLINUX_OBJS = $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
$(obj)/string.o $(obj)/cmdline.o $(obj)/early_serial_console.o \
- $(obj)/piggy.o
+ $(obj)/piggy.o $(obj)/cpuflags.o

$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone

diff --git a/arch/x86/boot/compressed/cpuflags.c b/arch/x86/boot/compressed/cpuflags.c
new file mode 100644
index 0000000..931cba6
--- /dev/null
+++ b/arch/x86/boot/compressed/cpuflags.c
@@ -0,0 +1,12 @@
+#ifdef CONFIG_RANDOMIZE_BASE
+
+#include "../cpuflags.c"
+
+bool has_cpuflag(int flag)
+{
+ get_flags();
+
+ return test_bit(flag, cpu.flags);
+}
+
+#endif
diff --git a/arch/x86/boot/cpucheck.c b/arch/x86/boot/cpucheck.c
index 4d3ff03..e1f3c16 100644
--- a/arch/x86/boot/cpucheck.c
+++ b/arch/x86/boot/cpucheck.c
@@ -28,8 +28,6 @@
#include <asm/required-features.h>
#include <asm/msr-index.h>

-struct cpu_features cpu;
-static u32 cpu_vendor[3];
static u32 err_flags[NCAPINTS];

static const int req_level = CONFIG_X86_MINIMUM_CPU_FAMILY;
@@ -69,90 +67,6 @@ static int is_transmeta(void)
cpu_vendor[2] == A32('M', 'x', '8', '6');
}

-static int has_fpu(void)
-{
- u16 fcw = -1, fsw = -1;
- u32 cr0;
-
- asm("movl %%cr0,%0" : "=r" (cr0));
- if (cr0 & (X86_CR0_EM|X86_CR0_TS)) {
- cr0 &= ~(X86_CR0_EM|X86_CR0_TS);
- asm volatile("movl %0,%%cr0" : : "r" (cr0));
- }
-
- asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
- : "+m" (fsw), "+m" (fcw));
-
- return fsw == 0 && (fcw & 0x103f) == 0x003f;
-}
-
-static int has_eflag(u32 mask)
-{
- u32 f0, f1;
-
- asm("pushfl ; "
- "pushfl ; "
- "popl %0 ; "
- "movl %0,%1 ; "
- "xorl %2,%1 ; "
- "pushl %1 ; "
- "popfl ; "
- "pushfl ; "
- "popl %1 ; "
- "popfl"
- : "=&r" (f0), "=&r" (f1)
- : "ri" (mask));
-
- return !!((f0^f1) & mask);
-}
-
-static void get_flags(void)
-{
- u32 max_intel_level, max_amd_level;
- u32 tfms;
-
- if (has_fpu())
- set_bit(X86_FEATURE_FPU, cpu.flags);
-
- if (has_eflag(X86_EFLAGS_ID)) {
- asm("cpuid"
- : "=a" (max_intel_level),
- "=b" (cpu_vendor[0]),
- "=d" (cpu_vendor[1]),
- "=c" (cpu_vendor[2])
- : "a" (0));
-
- if (max_intel_level >= 0x00000001 &&
- max_intel_level <= 0x0000ffff) {
- asm("cpuid"
- : "=a" (tfms),
- "=c" (cpu.flags[4]),
- "=d" (cpu.flags[0])
- : "a" (0x00000001)
- : "ebx");
- cpu.level = (tfms >> 8) & 15;
- cpu.model = (tfms >> 4) & 15;
- if (cpu.level >= 6)
- cpu.model += ((tfms >> 16) & 0xf) << 4;
- }
-
- asm("cpuid"
- : "=a" (max_amd_level)
- : "a" (0x80000000)
- : "ebx", "ecx", "edx");
-
- if (max_amd_level >= 0x80000001 &&
- max_amd_level <= 0x8000ffff) {
- u32 eax = 0x80000001;
- asm("cpuid"
- : "+a" (eax),
- "=c" (cpu.flags[6]),
- "=d" (cpu.flags[1])
- : : "ebx");
- }
- }
-}
-
/* Returns a bitmask of which words we have error bits in */
static int check_flags(void)
{
diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
new file mode 100644
index 0000000..e05207d
--- /dev/null
+++ b/arch/x86/boot/cpuflags.c
@@ -0,0 +1,109 @@
+#include <linux/types.h>
+#include "bitops.h"
+
+#include <asm/processor-flags.h>
+#include <asm/required-features.h>
+#include <asm/msr-index.h>
+#include "cpuflags.h"
+
+struct cpu_features cpu;
+u32 cpu_vendor[3];
+
+static bool loaded_flags;
+
+static int has_fpu(void)
+{
+#ifdef __i386__
+ u16 fcw = -1, fsw = -1;
+ u32 cr0;
+
+ asm volatile("movl %%cr0,%0" : "=r" (cr0));
+ if (cr0 & (X86_CR0_EM|X86_CR0_TS)) {
+ cr0 &= ~(X86_CR0_EM|X86_CR0_TS);
+ asm volatile("movl %0,%%cr0" : : "r" (cr0));
+ }
+
+ asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
+ : "+m" (fsw), "+m" (fcw));
+
+ return fsw == 0 && (fcw & 0x103f) == 0x003f;
+#else
+ return 1;
+#endif
+}
+
+int has_eflag(u32 mask)
+{
+#ifdef __i386__
+ u32 f0, f1;
+
+ asm volatile("pushfl \n\t"
+ "pushfl \n\t"
+ "popl %0 \n\t"
+ "movl %0,%1\n\t"
+ "xorl %2,%1\n\t"
+ "pushl %1 \n\t"
+ "popfl \n\t"
+ "pushfl \n\t"
+ "popl %1 \n\t"
+ "popfl"
+ : "=&r" (f0), "=&r" (f1)
+ : "ri" (mask));
+
+ return !!((f0^f1) & mask);
+#else
+ return 1;
+#endif
+}
+
+static inline void cpuid(u32 id, u32 *a, u32 *b, u32 *c, u32 *d)
+{
+ /* Handle x86_32 PIC using ebx. */
+ asm volatile("movl %%ebx, %%edi \n\t"
+ "cpuid \n\t"
+ "xchgl %%edi, %%ebx\n\t"
+ : "=a" (*a),
+ "=D" (*b),
+ "=c" (*c),
+ "=d" (*d)
+ : "a" (id)
+ );
+}
+
+void get_flags(void)
+{
+ u32 max_intel_level, max_amd_level;
+ u32 tfms;
+ u32 ignored;
+
+ if (loaded_flags)
+ return;
+ loaded_flags = true;
+
+ if (has_fpu())
+ set_bit(X86_FEATURE_FPU, cpu.flags);
+
+ if (has_eflag(X86_EFLAGS_ID)) {
+ cpuid(0x0, &max_intel_level, &cpu_vendor[0], &cpu_vendor[2],
+ &cpu_vendor[1]);
+
+ if (max_intel_level >= 0x00000001 &&
+ max_intel_level <= 0x0000ffff) {
+ cpuid(0x1, &tfms, &ignored, &cpu.flags[4],
+ &cpu.flags[0]);
+ cpu.level = (tfms >> 8) & 15;
+ cpu.model = (tfms >> 4) & 15;
+ if (cpu.level >= 6)
+ cpu.model += ((tfms >> 16) & 0xf) << 4;
+ }
+
+ cpuid(0x80000000, &max_amd_level, &ignored, &ignored,
+ &ignored);
+
+ if (max_amd_level >= 0x80000001 &&
+ max_amd_level <= 0x8000ffff) {
+ cpuid(0x80000001, &ignored, &ignored, &cpu.flags[6],
+ &cpu.flags[1]);
+ }
+ }
+}
diff --git a/arch/x86/boot/cpuflags.h b/arch/x86/boot/cpuflags.h
new file mode 100644
index 0000000..dcfdc0c
--- /dev/null
+++ b/arch/x86/boot/cpuflags.h
@@ -0,0 +1,19 @@
+#ifndef BOOT_CPUFLAGS_H
+#define BOOT_CPUFLAGS_H
+
+#include <asm/cpufeature.h>
+#include <asm/processor-flags.h>
+
+struct cpu_features {
+ int level; /* Family, or 64 for x86-64 */
+ int model;
+ u32 flags[NCAPINTS];
+};
+
+extern struct cpu_features cpu;
+extern u32 cpu_vendor[3];
+
+int has_eflag(u32 mask);
+void get_flags(void);
+
+#endif
--
1.7.9.5