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| author |   Kees Cook <keescook@chromium.org> | 2013-10-10 17:18:15 -0700 |
|---|---|---|
| committer |   H. Peter Anvin <hpa@linux.intel.com> | 2013-10-13 03:12:12 -0700 |
| commit | 5bfce5ef55cbe78ee2ee6e97f2e26a8a582008f3 (patch) | |
| tree | ead4a5281554b6f2e0a334cc7e1d83dccf35e15c /arch/x86/boot/compressed/aslr.c | |
| parent | x86, kaslr: Return location from decompress_kernel (diff) | |
| download | linux-dev-5bfce5ef55cbe78ee2ee6e97f2e26a8a582008f3.tar.xz linux-dev-5bfce5ef55cbe78ee2ee6e97f2e26a8a582008f3.zip | |
x86, kaslr: Provide randomness functions
Adds potential sources of randomness: RDRAND, RDTSC, or the i8254.
This moves the pre-alternatives inline rdrand function into the header so
both pieces of code can use it. Availability of RDRAND is then controlled
by CONFIG_ARCH_RANDOM, if someone wants to disable it even for kASLR.
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/1381450698-28710-4-git-send-email-keescook@chromium.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/boot/compressed/aslr.c')
| -rw-r--r-- | arch/x86/boot/compressed/aslr.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c index b73cc66d201e..14b24e0e5496 100644 --- a/arch/x86/boot/compressed/aslr.c +++ b/arch/x86/boot/compressed/aslr.c @@ -1,6 +1,59 @@ #include "misc.h" #ifdef CONFIG_RANDOMIZE_BASE +#include <asm/msr.h> +#include <asm/archrandom.h> + +#define I8254_PORT_CONTROL 0x43 +#define I8254_PORT_COUNTER0 0x40 +#define I8254_CMD_READBACK 0xC0 +#define I8254_SELECT_COUNTER0 0x02 +#define I8254_STATUS_NOTREADY 0x40 +static inline u16 i8254(void) +{ + u16 status, timer; + + do { + outb(I8254_PORT_CONTROL, + I8254_CMD_READBACK | I8254_SELECT_COUNTER0); + status = inb(I8254_PORT_COUNTER0); + timer = inb(I8254_PORT_COUNTER0); + timer |= inb(I8254_PORT_COUNTER0) << 8; + } while (status & I8254_STATUS_NOTREADY); + + return timer; +} + +static unsigned long get_random_long(void) +{ + unsigned long random; + + if (has_cpuflag(X86_FEATURE_RDRAND)) { + debug_putstr("KASLR using RDRAND...\n"); + if (rdrand_long(&random)) + return random; + } + + if (has_cpuflag(X86_FEATURE_TSC)) { + uint32_t raw; + + debug_putstr("KASLR using RDTSC...\n"); + rdtscl(raw); + + /* Only use the low bits of rdtsc. */ + random = raw & 0xffff; + } else { + debug_putstr("KASLR using i8254...\n"); + random = i8254(); + } + + /* Extend timer bits poorly... */ + random |= (random << 16); +#ifdef CONFIG_X86_64 + random |= (random << 32); +#endif + return random; +} unsigned char *choose_kernel_location(unsigned char *input, unsigned long input_size, |