1 files changed, 198 insertions, 81 deletions

diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h
index 775816965c6a..9b2a0ff76c73 100644
--- a/arch/x86/include/asm/irq_stack.h
+++ b/arch/x86/include/asm/irq_stack.h
@@ -7,100 +7,217 @@
 #include <asm/processor.h>
 
 #ifdef CONFIG_X86_64
-static __always_inline bool irqstack_active(void)
-{
-	return __this_cpu_read(irq_count) != -1;
-}
-
-void asm_call_on_stack(void *sp, void (*func)(void), void *arg);
-void asm_call_sysvec_on_stack(void *sp, void (*func)(struct pt_regs *regs),
-			      struct pt_regs *regs);
-void asm_call_irq_on_stack(void *sp, void (*func)(struct irq_desc *desc),
-			   struct irq_desc *desc);
 
-static __always_inline void __run_on_irqstack(void (*func)(void))
-{
-	void *tos = __this_cpu_read(hardirq_stack_ptr);
-
-	__this_cpu_add(irq_count, 1);
-	asm_call_on_stack(tos - 8, func, NULL);
-	__this_cpu_sub(irq_count, 1);
+/*
+ * Macro to inline switching to an interrupt stack and invoking function
+ * calls from there. The following rules apply:
+ *
+ * - Ordering:
+ *
+ *   1. Write the stack pointer into the top most place of the irq
+ *	stack. This ensures that the various unwinders can link back to the
+ *	original stack.
+ *
+ *   2. Switch the stack pointer to the top of the irq stack.
+ *
+ *   3. Invoke whatever needs to be done (@asm_call argument)
+ *
+ *   4. Pop the original stack pointer from the top of the irq stack
+ *	which brings it back to the original stack where it left off.
+ *
+ * - Function invocation:
+ *
+ *   To allow flexible usage of the macro, the actual function code including
+ *   the store of the arguments in the call ABI registers is handed in via
+ *   the @asm_call argument.
+ *
+ * - Local variables:
+ *
+ *   @tos:
+ *	The @tos variable holds a pointer to the top of the irq stack and
+ *	_must_ be allocated in a non-callee saved register as this is a
+ *	restriction coming from objtool.
+ *
+ *	Note, that (tos) is both in input and output constraints to ensure
+ *	that the compiler does not assume that R11 is left untouched in
+ *	case this macro is used in some place where the per cpu interrupt
+ *	stack pointer is used again afterwards
+ *
+ * - Function arguments:
+ *	The function argument(s), if any, have to be defined in register
+ *	variables at the place where this is invoked. Storing the
+ *	argument(s) in the proper register(s) is part of the @asm_call
+ *
+ * - Constraints:
+ *
+ *   The constraints have to be done very carefully because the compiler
+ *   does not know about the assembly call.
+ *
+ *   output:
+ *     As documented already above the @tos variable is required to be in
+ *     the output constraints to make the compiler aware that R11 cannot be
+ *     reused after the asm() statement.
+ *
+ *     For builds with CONFIG_UNWIND_FRAME_POINTER ASM_CALL_CONSTRAINT is
+ *     required as well as this prevents certain creative GCC variants from
+ *     misplacing the ASM code.
+ *
+ *  input:
+ *    - func:
+ *	  Immediate, which tells the compiler that the function is referenced.
+ *
+ *    - tos:
+ *	  Register. The actual register is defined by the variable declaration.
+ *
+ *    - function arguments:
+ *	  The constraints are handed in via the 'argconstr' argument list. They
+ *	  describe the register arguments which are used in @asm_call.
+ *
+ *  clobbers:
+ *     Function calls can clobber anything except the callee-saved
+ *     registers. Tell the compiler.
+ */
+#define call_on_irqstack(func, asm_call, argconstr...)			\
+{									\
+	register void *tos asm("r11");					\
+									\
+	tos = ((void *)__this_cpu_read(hardirq_stack_ptr));		\
+									\
+	asm_inline volatile(						\
+	"movq	%%rsp, (%[tos])				\n"		\
+	"movq	%[tos], %%rsp				\n"		\
+									\
+	asm_call							\
+									\
+	"popq	%%rsp					\n"		\
+									\
+	: "+r" (tos), ASM_CALL_CONSTRAINT				\
+	: [__func] "i" (func), [tos] "r" (tos) argconstr		\
+	: "cc", "rax", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10",	\
+	  "memory"							\
+	);								\
 }
 
-static __always_inline void
-__run_sysvec_on_irqstack(void (*func)(struct pt_regs *regs),
-			 struct pt_regs *regs)
-{
-	void *tos = __this_cpu_read(hardirq_stack_ptr);
-
-	__this_cpu_add(irq_count, 1);
-	asm_call_sysvec_on_stack(tos - 8, func, regs);
-	__this_cpu_sub(irq_count, 1);
+/* Macros to assert type correctness for run_*_on_irqstack macros */
+#define assert_function_type(func, proto)				\
+	static_assert(__builtin_types_compatible_p(typeof(&func), proto))
+
+#define assert_arg_type(arg, proto)					\
+	static_assert(__builtin_types_compatible_p(typeof(arg), proto))
+
+/*
+ * Macro to invoke system vector and device interrupt C handlers.
+ */
+#define call_on_irqstack_cond(func, regs, asm_call, constr, c_args...)	\
+{									\
+	/*								\
+	 * User mode entry and interrupt on the irq stack do not	\
+	 * switch stacks. If from user mode the task stack is empty.	\
+	 */								\
+	if (user_mode(regs) || __this_cpu_read(hardirq_stack_inuse)) {	\
+		irq_enter_rcu();					\
+		func(c_args);						\
+		irq_exit_rcu();						\
+	} else {							\
+		/*							\
+		 * Mark the irq stack inuse _before_ and unmark _after_	\
+		 * switching stacks. Interrupts are disabled in both	\
+		 * places. Invoke the stack switch macro with the call	\
+		 * sequence which matches the above direct invocation.	\
+		 */							\
+		__this_cpu_write(hardirq_stack_inuse, true);		\
+		call_on_irqstack(func, asm_call, constr);		\
+		__this_cpu_write(hardirq_stack_inuse, false);		\
+	}								\
 }
 
-static __always_inline void
-__run_irq_on_irqstack(void (*func)(struct irq_desc *desc),
-		      struct irq_desc *desc)
-{
-	void *tos = __this_cpu_read(hardirq_stack_ptr);
-
-	__this_cpu_add(irq_count, 1);
-	asm_call_irq_on_stack(tos - 8, func, desc);
-	__this_cpu_sub(irq_count, 1);
+/*
+ * Function call sequence for __call_on_irqstack() for system vectors.
+ *
+ * Note that irq_enter_rcu() and irq_exit_rcu() do not use the input
+ * mechanism because these functions are global and cannot be optimized out
+ * when compiling a particular source file which uses one of these macros.
+ *
+ * The argument (regs) does not need to be pushed or stashed in a callee
+ * saved register to be safe vs. the irq_enter_rcu() call because the
+ * clobbers already prevent the compiler from storing it in a callee
+ * clobbered register. As the compiler has to preserve @regs for the final
+ * call to idtentry_exit() anyway, it's likely that it does not cause extra
+ * effort for this asm magic.
+ */
+#define ASM_CALL_SYSVEC							\
+	"call irq_enter_rcu				\n"		\
+	"movq	%[arg1], %%rdi				\n"		\
+	"call %P[__func]				\n"		\
+	"call irq_exit_rcu				\n"
+
+#define SYSVEC_CONSTRAINTS	, [arg1] "r" (regs)
+
+#define run_sysvec_on_irqstack_cond(func, regs)				\
+{									\
+	assert_function_type(func, void (*)(struct pt_regs *));		\
+	assert_arg_type(regs, struct pt_regs *);			\
+									\
+	call_on_irqstack_cond(func, regs, ASM_CALL_SYSVEC,		\
+			      SYSVEC_CONSTRAINTS, regs);		\
 }
 
-#else /* CONFIG_X86_64 */
-static inline bool irqstack_active(void) { return false; }
-static inline void __run_on_irqstack(void (*func)(void)) { }
-static inline void __run_sysvec_on_irqstack(void (*func)(struct pt_regs *regs),
-					    struct pt_regs *regs) { }
-static inline void __run_irq_on_irqstack(void (*func)(struct irq_desc *desc),
-					 struct irq_desc *desc) { }
-#endif /* !CONFIG_X86_64 */
-
-static __always_inline bool irq_needs_irq_stack(struct pt_regs *regs)
-{
-	if (IS_ENABLED(CONFIG_X86_32))
-		return false;
-	if (!regs)
-		return !irqstack_active();
-	return !user_mode(regs) && !irqstack_active();
+/*
+ * As in ASM_CALL_SYSVEC above the clobbers force the compiler to store
+ * @regs and @vector in callee saved registers.
+ */
+#define ASM_CALL_IRQ							\
+	"call irq_enter_rcu				\n"		\
+	"movq	%[arg1], %%rdi				\n"		\
+	"movl	%[arg2], %%esi				\n"		\
+	"call %P[__func]				\n"		\
+	"call irq_exit_rcu				\n"
+
+#define IRQ_CONSTRAINTS	, [arg1] "r" (regs), [arg2] "r" (vector)
+
+#define run_irq_on_irqstack_cond(func, regs, vector)			\
+{									\
+	assert_function_type(func, void (*)(struct pt_regs *, u32));	\
+	assert_arg_type(regs, struct pt_regs *);			\
+	assert_arg_type(vector, u32);					\
+									\
+	call_on_irqstack_cond(func, regs, ASM_CALL_IRQ,			\
+			      IRQ_CONSTRAINTS, regs, vector);		\
 }
 
-
-static __always_inline void run_on_irqstack_cond(void (*func)(void),
-						 struct pt_regs *regs)
-{
-	lockdep_assert_irqs_disabled();
-
-	if (irq_needs_irq_stack(regs))
-		__run_on_irqstack(func);
-	else
-		func();
+#define ASM_CALL_SOFTIRQ						\
+	"call %P[__func]				\n"
+
+/*
+ * Macro to invoke __do_softirq on the irq stack. This is only called from
+ * task context when bottom halfs are about to be reenabled and soft
+ * interrupts are pending to be processed. The interrupt stack cannot be in
+ * use here.
+ */
+#define do_softirq_own_stack()						\
+{									\
+	__this_cpu_write(hardirq_stack_inuse, true);			\
+	call_on_irqstack(__do_softirq, ASM_CALL_SOFTIRQ);		\
+	__this_cpu_write(hardirq_stack_inuse, false);			\
 }
 
-static __always_inline void
-run_sysvec_on_irqstack_cond(void (*func)(struct pt_regs *regs),
-			    struct pt_regs *regs)
-{
-	lockdep_assert_irqs_disabled();
-
-	if (irq_needs_irq_stack(regs))
-		__run_sysvec_on_irqstack(func, regs);
-	else
-		func(regs);
+#else /* CONFIG_X86_64 */
+/* System vector handlers always run on the stack they interrupted. */
+#define run_sysvec_on_irqstack_cond(func, regs)				\
+{									\
+	irq_enter_rcu();						\
+	func(regs);							\
+	irq_exit_rcu();							\
 }
 
-static __always_inline void
-run_irq_on_irqstack_cond(void (*func)(struct irq_desc *desc), struct irq_desc *desc,
-			 struct pt_regs *regs)
-{
-	lockdep_assert_irqs_disabled();
-
-	if (irq_needs_irq_stack(regs))
-		__run_irq_on_irqstack(func, desc);
-	else
-		func(desc);
+/* Switches to the irq stack within func() */
+#define run_irq_on_irqstack_cond(func, regs, vector)			\
+{									\
+	irq_enter_rcu();						\
+	func(regs, vector);						\
+	irq_exit_rcu();							\
 }
 
+#endif /* !CONFIG_X86_64 */
+
 #endif