diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/elf.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/amd.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/sys_x86_64.c | 30 |
3 files changed, 32 insertions, 3 deletions
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index ca3347a9dab5..bd292ce9be0a 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -365,6 +365,7 @@ enum align_flags { struct va_alignment { int flags; unsigned long mask; + unsigned long bits; } ____cacheline_aligned; extern struct va_alignment va_align; diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index a220239cea65..ec6a61b21b41 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -5,6 +5,7 @@ #include <linux/io.h> #include <linux/sched.h> +#include <linux/random.h> #include <asm/processor.h> #include <asm/apic.h> #include <asm/cpu.h> @@ -488,6 +489,9 @@ static void bsp_init_amd(struct cpuinfo_x86 *c) va_align.mask = (upperbit - 1) & PAGE_MASK; va_align.flags = ALIGN_VA_32 | ALIGN_VA_64; + + /* A random value per boot for bit slice [12:upper_bit) */ + va_align.bits = get_random_int() & va_align.mask; } } diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index 30277e27431a..10e0272d789a 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -34,10 +34,26 @@ static unsigned long get_align_mask(void) return va_align.mask; } +/* + * To avoid aliasing in the I$ on AMD F15h, the bits defined by the + * va_align.bits, [12:upper_bit), are set to a random value instead of + * zeroing them. This random value is computed once per boot. This form + * of ASLR is known as "per-boot ASLR". + * + * To achieve this, the random value is added to the info.align_offset + * value before calling vm_unmapped_area() or ORed directly to the + * address. + */ +static unsigned long get_align_bits(void) +{ + return va_align.bits & get_align_mask(); +} + unsigned long align_vdso_addr(unsigned long addr) { unsigned long align_mask = get_align_mask(); - return (addr + align_mask) & ~align_mask; + addr = (addr + align_mask) & ~align_mask; + return addr | get_align_bits(); } static int __init control_va_addr_alignment(char *str) @@ -135,8 +151,12 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, info.length = len; info.low_limit = begin; info.high_limit = end; - info.align_mask = filp ? get_align_mask() : 0; + info.align_mask = 0; info.align_offset = pgoff << PAGE_SHIFT; + if (filp) { + info.align_mask = get_align_mask(); + info.align_offset += get_align_bits(); + } return vm_unmapped_area(&info); } @@ -174,8 +194,12 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, info.length = len; info.low_limit = PAGE_SIZE; info.high_limit = mm->mmap_base; - info.align_mask = filp ? get_align_mask() : 0; + info.align_mask = 0; info.align_offset = pgoff << PAGE_SHIFT; + if (filp) { + info.align_mask = get_align_mask(); + info.align_offset += get_align_bits(); + } addr = vm_unmapped_area(&info); if (!(addr & ~PAGE_MASK)) return addr; |