diff options
Diffstat (limited to 'arch/x86/include/asm/switch_to.h')
| -rw-r--r-- | arch/x86/include/asm/switch_to.h | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index 751bf4b7bf11..025ecfaba9c9 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -1,6 +1,8 @@ #ifndef _ASM_X86_SWITCH_TO_H #define _ASM_X86_SWITCH_TO_H +#include <asm/nospec-branch.h> + struct task_struct; /* one of the stranger aspects of C forward declarations */ __visible struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next); @@ -24,6 +26,23 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, #define __switch_canary_iparam #endif /* CC_STACKPROTECTOR */ +#ifdef CONFIG_RETPOLINE + /* + * When switching from a shallower to a deeper call stack + * the RSB may either underflow or use entries populated + * with userspace addresses. On CPUs where those concerns + * exist, overwrite the RSB with entries which capture + * speculative execution to prevent attack. + */ +#define __retpoline_fill_return_buffer \ + ALTERNATIVE("jmp 910f", \ + __stringify(__FILL_RETURN_BUFFER(%%ebx, RSB_CLEAR_LOOPS, %%esp)),\ + X86_FEATURE_RSB_CTXSW) \ + "910:\n\t" +#else +#define __retpoline_fill_return_buffer +#endif + /* * Saving eflags is important. It switches not only IOPL between tasks, * it also protects other tasks from NT leaking through sysenter etc. @@ -46,6 +65,7 @@ do { \ "movl $1f,%[prev_ip]\n\t" /* save EIP */ \ "pushl %[next_ip]\n\t" /* restore EIP */ \ __switch_canary \ + __retpoline_fill_return_buffer \ "jmp __switch_to\n" /* regparm call */ \ "1:\t" \ "popl %%ebp\n\t" /* restore EBP */ \ @@ -100,6 +120,23 @@ do { \ #define __switch_canary_iparam #endif /* CC_STACKPROTECTOR */ +#ifdef CONFIG_RETPOLINE + /* + * When switching from a shallower to a deeper call stack + * the RSB may either underflow or use entries populated + * with userspace addresses. On CPUs where those concerns + * exist, overwrite the RSB with entries which capture + * speculative execution to prevent attack. + */ +#define __retpoline_fill_return_buffer \ + ALTERNATIVE("jmp 910f", \ + __stringify(__FILL_RETURN_BUFFER(%%r12, RSB_CLEAR_LOOPS, %%rsp)),\ + X86_FEATURE_RSB_CTXSW) \ + "910:\n\t" +#else +#define __retpoline_fill_return_buffer +#endif + /* * There is no need to save or restore flags, because flags are always * clean in kernel mode, with the possible exception of IOPL. Kernel IOPL @@ -112,6 +149,7 @@ do { \ "call __switch_to\n\t" \ "movq "__percpu_arg([current_task])",%%rsi\n\t" \ __switch_canary \ + __retpoline_fill_return_buffer \ "movq %P[thread_info](%%rsi),%%r8\n\t" \ "movq %%rax,%%rdi\n\t" \ "testl %[_tif_fork],%P[ti_flags](%%r8)\n\t" \ |