write in 30M

hc

2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc

 kernel/arch/x86/include/asm/switch_to.h
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@@ -12,27 +12,6 @@
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 __visible struct task_struct *__switch_to(struct task_struct *prev,
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 					  struct task_struct *next);
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-/* This runs runs on the previous thread's stack. */
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-static inline void prepare_switch_to(struct task_struct *next)
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-{
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-#ifdef CONFIG_VMAP_STACK
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-	/*
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-	 * If we switch to a stack that has a top-level paging entry
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-	 * that is not present in the current mm, the resulting #PF will
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-	 * will be promoted to a double-fault and we'll panic.  Probe
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-	 * the new stack now so that vmalloc_fault can fix up the page
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-	 * tables if needed.  This can only happen if we use a stack
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-	 * in vmap space.
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-	 *
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-	 * We assume that the stack is aligned so that it never spans
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-	 * more than one top-level paging entry.
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-	 *
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-	 * To minimize cache pollution, just follow the stack pointer.
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-	 */
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-	READ_ONCE(*(unsigned char *)next->thread.sp);
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-#endif
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-}
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-
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 asmlinkage void ret_from_fork(void);
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 /*
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@@ -40,13 +19,13 @@
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  * order of the fields must match the code in __switch_to_asm().
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  */
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 struct inactive_task_frame {
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-	unsigned long flags;
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 #ifdef CONFIG_X86_64
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 	unsigned long r15;
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 	unsigned long r14;
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 	unsigned long r13;
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 	unsigned long r12;
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 #else
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+	unsigned long flags;
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 	unsigned long si;
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 	unsigned long di;
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 #endif
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@@ -67,8 +46,6 @@
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 #define switch_to(prev, next, last)					\
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 do {									\
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-	prepare_switch_to(next);					\
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-									\
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 	((last) = __switch_to_asm((prev), (next)));			\
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 } while (0)
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@@ -103,7 +80,17 @@
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 	if (static_cpu_has(X86_FEATURE_XENPV))
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 		load_sp0(task_top_of_stack(task));
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 #endif
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+}
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+static inline void kthread_frame_init(struct inactive_task_frame *frame,
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+				      unsigned long fun, unsigned long arg)
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+{
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+	frame->bx = fun;
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+#ifdef CONFIG_X86_32
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+	frame->di = arg;
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+#else
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+	frame->r12 = arg;
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+#endif
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 }
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 #endif /* _ASM_X86_SWITCH_TO_H */