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-rw-r--r--arch/x86/include/asm/entry-common.h99
1 files changed, 99 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 000000000..11203a9fe
--- /dev/null
+++ b/arch/x86/include/asm/entry-common.h
@@ -0,0 +1,99 @@
+/* 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_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 (boot_cpu_has(X86_FEATURE_SMAP) ||
+ (IS_ENABLED(CONFIG_64BIT) && 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_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)
+{
+ 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();
+ amd_clear_divider();
+}
+#define arch_exit_to_user_mode arch_exit_to_user_mode
+
+#endif