1 files changed, 112 insertions, 0 deletions
diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h
new file mode 100644
index 000000000000..ce3eb6d5fdf9
--- /dev/null
+++ b/arch/x86/include/asm/entry-common.h
@@ -0,0 +1,112 @@
+/* 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>
+#include <asm/fred.h>
+
+/* Check that the stack and regs on entry from user mode are sane. */
+static __always_inline void arch_enter_from_user_mode(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 (cpu_feature_enabled(X86_FEATURE_SMAP) ||
+		    cpu_feature_enabled(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_enter_from_user_mode arch_enter_from_user_mode
+
+static inline void arch_exit_work(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();
+
+	if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
+		switch_fpu_return();
+}
+
+static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
+						  unsigned long ti_work)
+{
+	fpregs_assert_state_consistent();
+
+	if (unlikely(ti_work))
+		arch_exit_work(ti_work);
+
+	fred_update_rsp0();
+
+#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
+
+	/*
+	 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
+	 * 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 7 (x86_64) or
+	 * 8 (ia32) bits.
+	 */
+	choose_random_kstack_offset(rdtsc());
+
+	/* Avoid unnecessary reads of 'x86_ibpb_exit_to_user' */
+	if (cpu_feature_enabled(X86_FEATURE_IBPB_EXIT_TO_USER) &&
+	    this_cpu_read(x86_ibpb_exit_to_user)) {
+		indirect_branch_prediction_barrier();
+		this_cpu_write(x86_ibpb_exit_to_user, false);
+	}
+}
+#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
+
+static __always_inline void arch_exit_to_user_mode(void)
+{
+	amd_clear_divider();
+}
+#define arch_exit_to_user_mode arch_exit_to_user_mode
+
+#endif