x86/entry/64: Make cpu_entry_area.tss read-only

[thirdparty/kernel/stable.git] / arch / x86 / include / asm / switch_to.h

diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index fcc5cd387fd17a59e5f28ba5fc8fb65fc57ae5af..9b6df68d8fd1eba26f3651faa5c8b8f4dcf223f1 100644 (file)
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -1,6 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _ASM_X86_SWITCH_TO_H
 #define _ASM_X86_SWITCH_TO_H
 
+#include <linux/sched/task_stack.h>
+
 struct task_struct; /* one of the stranger aspects of C forward declarations */
 
 struct task_struct *__switch_to_asm(struct task_struct *prev,
@@ -72,4 +75,28 @@ do {                                                                 \
        ((last) = __switch_to_asm((prev), (next)));                     \
 } while (0)
 
+#ifdef CONFIG_X86_32
+static inline void refresh_sysenter_cs(struct thread_struct *thread)
+{
+       /* Only happens when SEP is enabled, no need to test "SEP"arately: */
+       if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
+               return;
+
+       this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
+       wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
+}
+#endif
+
+/* This is used when switching tasks or entering/exiting vm86 mode. */
+static inline void update_sp0(struct task_struct *task)
+{
+       /* On x86_64, sp0 always points to the entry trampoline stack, which is constant: */
+#ifdef CONFIG_X86_32
+       load_sp0(task->thread.sp0);
+#else
+       if (static_cpu_has(X86_FEATURE_XENPV))
+               load_sp0(task_top_of_stack(task));
+#endif
+}
+
 #endif /* _ASM_X86_SWITCH_TO_H */