On Thu, Apr 25, 2013 at 11:13 PM, Mathias Krause <[email protected]> wrote: > On Thu, Apr 25, 2013 at 11:54 PM, Kees Cook <[email protected]> wrote: >> Select a random location when CONFIG_RANDOMIZE_BASE is used, bounded >> by CONFIG_RANDOMIZE_BASE_MAX_OFFSET. Sources of randomness currently >> include RDRAND and RDTSC. >> >> Signed-off-by: Kees Cook <[email protected]> >> --- >> arch/x86/Kconfig | 29 +++++++++++++-- >> arch/x86/boot/compressed/aslr.c | 75 >> +++++++++++++++++++++++++++++++++++++-- >> 2 files changed, 100 insertions(+), 4 deletions(-) >> >> [snip] >> >> diff --git a/arch/x86/boot/compressed/aslr.c >> b/arch/x86/boot/compressed/aslr.c >> index d5331ee..11a91c6 100644 >> --- a/arch/x86/boot/compressed/aslr.c >> +++ b/arch/x86/boot/compressed/aslr.c >> @@ -2,18 +2,89 @@ >> >> #ifdef CONFIG_RANDOMIZE_BASE >> >> +#include <asm/archrandom.h> >> +static inline int rdrand(unsigned long *v) >> +{ >> + int ok; >> + asm volatile("1: " RDRAND_LONG "\n\t" >> + "jc 2f\n\t" >> + "decl %0\n\t" >> + "jnz 1b\n\t" >> + "2:" >> + : "=r" (ok), "=a" (*v) >> + : "0" (RDRAND_RETRY_LOOPS)); >> + return ok; >> +} >> + >> +static inline uint32_t rdtsc(void) >> +{ >> + uint32_t timer; >> + >> + asm volatile("rdtsc\n" : "=a" (timer)); > > '\n' in the assembly statement is not needed. Also, RDTSC trashes > edx/rdx as well so it should be mentioned in the clobber list, at > least. > Maybe using rdtscl() from <asm/msr.h> instead is an option?
Ah yeah, rdtscl is perfect. I'll use that instead. Thanks! -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
