/* SPDX-License-Identifier: GPL-2.0-only */ #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> #include <asm/io_bitmap.h> #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) { if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) { /* * Make sure that the entry code gave us a sensible EFLAGS * register. Native because we want to check the actual CPU * state, not the interrupt state as imagined by Xen. */ unsigned long flags = native_save_fl(); unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT; /* * 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))) mask |= X86_EFLAGS_AC; WARN_ON_ONCE(flags & mask); /* We think we came from user mode. Make sure pt_regs agrees. */ WARN_ON_ONCE(!user_mode(regs)); /* * All entries from user mode (except #DF) should be on the * normal thread stack and should have user pt_regs in the * correct location. */ WARN_ON_ONCE(!on_thread_stack()); WARN_ON_ONCE(regs != task_pt_regs(current)); } } #define arch_check_user_regs arch_check_user_regs static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs, unsigned long ti_work) { if (ti_work & _TIF_USER_RETURN_NOTIFY) fire_user_return_notifiers(); if (unlikely(ti_work & _TIF_IO_BITMAP)) tss_update_io_bitmap(); fpregs_assert_state_consistent(); if (unlikely(ti_work & _TIF_NEED_FPU_LOAD)) switch_fpu_return(); #ifdef CONFIG_COMPAT /* * Compat syscalls set TS_COMPAT. Make sure we clear it before * returning to user mode. We need to clear it *after* signal * handling, because syscall restart has a fixup for compat * syscalls. The fixup is exercised by the ptrace_syscall_32 * selftest. * * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer * special case only applies after poking regs and before the * very next return to user mode. */ 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 static __always_inline void arch_exit_to_user_mode(void) { mds_user_clear_cpu_buffers(); } #define arch_exit_to_user_mode arch_exit_to_user_mode #endif