diff options
Diffstat (limited to 'arch/x86/include/asm/entry-common.h')
| -rw-r--r-- | arch/x86/include/asm/entry-common.h | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h index 2b87b191b3b8..674ed46d3ced 100644 --- a/arch/x86/include/asm/entry-common.h +++ b/arch/x86/include/asm/entry-common.h @@ -2,6 +2,7 @@ #ifndef _ASM_X86_ENTRY_COMMON_H #define _ASM_X86_ENTRY_COMMON_H +#include <linux/randomize_kstack.h> #include <linux/user-return-notifier.h> #include <asm/nospec-branch.h> @@ -9,7 +10,7 @@ #include <asm/fpu/api.h> /* Check that the stack and regs on entry from user mode are sane. */ -static __always_inline void arch_check_user_regs(struct pt_regs *regs) +static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs) { if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) { /* @@ -24,7 +25,7 @@ static __always_inline void arch_check_user_regs(struct pt_regs *regs) * For !SMAP hardware we patch out CLAC on entry. */ if (boot_cpu_has(X86_FEATURE_SMAP) || - (IS_ENABLED(CONFIG_64_BIT) && boot_cpu_has(X86_FEATURE_XENPV))) + (IS_ENABLED(CONFIG_64BIT) && boot_cpu_has(X86_FEATURE_XENPV))) mask |= X86_EFLAGS_AC; WARN_ON_ONCE(flags & mask); @@ -41,7 +42,7 @@ static __always_inline void arch_check_user_regs(struct pt_regs *regs) WARN_ON_ONCE(regs != task_pt_regs(current)); } } -#define arch_check_user_regs arch_check_user_regs +#define arch_enter_from_user_mode arch_enter_from_user_mode static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs, unsigned long ti_work) @@ -70,6 +71,21 @@ static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs, */ current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED); #endif + + /* + * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(), + * but not enough for x86 stack utilization comfort. To keep + * reasonable stack head room, reduce the maximum offset to 8 bits. + * + * The actual entropy will be further reduced by the compiler when + * applying stack alignment constraints (see cc_stack_align4/8 in + * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32) + * low bits from any entropy chosen here. + * + * Therefore, final stack offset entropy will be 5 (x86_64) or + * 6 (ia32) bits. + */ + choose_random_kstack_offset(rdtsc() & 0xFF); } #define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare |