1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 #ifndef _ASM_X86_ENTRY_COMMON_H 3 #define _ASM_X86_ENTRY_COMMON_H 4 5 #include <linux/randomize_kstack.h> 6 #include <linux/user-return-notifier.h> 7 8 #include <asm/nospec-branch.h> 9 #include <asm/io_bitmap.h> 10 #include <asm/fpu/api.h> 11 12 /* Check that the stack and regs on entry from user mode are sane. */ 13 static __always_inline void arch_check_user_regs(struct pt_regs *regs) 14 { 15 if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) { 16 /* 17 * Make sure that the entry code gave us a sensible EFLAGS 18 * register. Native because we want to check the actual CPU 19 * state, not the interrupt state as imagined by Xen. 20 */ 21 unsigned long flags = native_save_fl(); 22 unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT; 23 24 /* 25 * For !SMAP hardware we patch out CLAC on entry. 26 */ 27 if (boot_cpu_has(X86_FEATURE_SMAP) || 28 (IS_ENABLED(CONFIG_64BIT) && boot_cpu_has(X86_FEATURE_XENPV))) 29 mask |= X86_EFLAGS_AC; 30 31 WARN_ON_ONCE(flags & mask); 32 33 /* We think we came from user mode. Make sure pt_regs agrees. */ 34 WARN_ON_ONCE(!user_mode(regs)); 35 36 /* 37 * All entries from user mode (except #DF) should be on the 38 * normal thread stack and should have user pt_regs in the 39 * correct location. 40 */ 41 WARN_ON_ONCE(!on_thread_stack()); 42 WARN_ON_ONCE(regs != task_pt_regs(current)); 43 } 44 } 45 #define arch_check_user_regs arch_check_user_regs 46 47 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs, 48 unsigned long ti_work) 49 { 50 if (ti_work & _TIF_USER_RETURN_NOTIFY) 51 fire_user_return_notifiers(); 52 53 if (unlikely(ti_work & _TIF_IO_BITMAP)) 54 tss_update_io_bitmap(); 55 56 fpregs_assert_state_consistent(); 57 if (unlikely(ti_work & _TIF_NEED_FPU_LOAD)) 58 switch_fpu_return(); 59 60 #ifdef CONFIG_COMPAT 61 /* 62 * Compat syscalls set TS_COMPAT. Make sure we clear it before 63 * returning to user mode. We need to clear it *after* signal 64 * handling, because syscall restart has a fixup for compat 65 * syscalls. The fixup is exercised by the ptrace_syscall_32 66 * selftest. 67 * 68 * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer 69 * special case only applies after poking regs and before the 70 * very next return to user mode. 71 */ 72 current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED); 73 #endif 74 75 /* 76 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(), 77 * but not enough for x86 stack utilization comfort. To keep 78 * reasonable stack head room, reduce the maximum offset to 8 bits. 79 * 80 * The actual entropy will be further reduced by the compiler when 81 * applying stack alignment constraints (see cc_stack_align4/8 in 82 * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32) 83 * low bits from any entropy chosen here. 84 * 85 * Therefore, final stack offset entropy will be 5 (x86_64) or 86 * 6 (ia32) bits. 87 */ 88 choose_random_kstack_offset(rdtsc() & 0xFF); 89 } 90 #define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare 91 92 static __always_inline void arch_exit_to_user_mode(void) 93 { 94 mds_user_clear_cpu_buffers(); 95 } 96 #define arch_exit_to_user_mode arch_exit_to_user_mode 97 98 #endif 99