xref: /openbmc/linux/arch/x86/kernel/irq_32.c (revision 4f205687)
1 /*
2  *	Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
3  *
4  * This file contains the lowest level x86-specific interrupt
5  * entry, irq-stacks and irq statistics code. All the remaining
6  * irq logic is done by the generic kernel/irq/ code and
7  * by the x86-specific irq controller code. (e.g. i8259.c and
8  * io_apic.c.)
9  */
10 
11 #include <linux/module.h>
12 #include <linux/seq_file.h>
13 #include <linux/interrupt.h>
14 #include <linux/kernel_stat.h>
15 #include <linux/notifier.h>
16 #include <linux/cpu.h>
17 #include <linux/delay.h>
18 #include <linux/uaccess.h>
19 #include <linux/percpu.h>
20 #include <linux/mm.h>
21 
22 #include <asm/apic.h>
23 
24 #ifdef CONFIG_DEBUG_STACKOVERFLOW
25 
26 int sysctl_panic_on_stackoverflow __read_mostly;
27 
28 /* Debugging check for stack overflow: is there less than 1KB free? */
29 static int check_stack_overflow(void)
30 {
31 	long sp;
32 
33 	__asm__ __volatile__("andl %%esp,%0" :
34 			     "=r" (sp) : "0" (THREAD_SIZE - 1));
35 
36 	return sp < (sizeof(struct thread_info) + STACK_WARN);
37 }
38 
39 static void print_stack_overflow(void)
40 {
41 	printk(KERN_WARNING "low stack detected by irq handler\n");
42 	dump_stack();
43 	if (sysctl_panic_on_stackoverflow)
44 		panic("low stack detected by irq handler - check messages\n");
45 }
46 
47 #else
48 static inline int check_stack_overflow(void) { return 0; }
49 static inline void print_stack_overflow(void) { }
50 #endif
51 
52 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
53 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
54 
55 static void call_on_stack(void *func, void *stack)
56 {
57 	asm volatile("xchgl	%%ebx,%%esp	\n"
58 		     "call	*%%edi		\n"
59 		     "movl	%%ebx,%%esp	\n"
60 		     : "=b" (stack)
61 		     : "0" (stack),
62 		       "D"(func)
63 		     : "memory", "cc", "edx", "ecx", "eax");
64 }
65 
66 static inline void *current_stack(void)
67 {
68 	return (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
69 }
70 
71 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
72 {
73 	struct irq_stack *curstk, *irqstk;
74 	u32 *isp, *prev_esp, arg1;
75 
76 	curstk = (struct irq_stack *) current_stack();
77 	irqstk = __this_cpu_read(hardirq_stack);
78 
79 	/*
80 	 * this is where we switch to the IRQ stack. However, if we are
81 	 * already using the IRQ stack (because we interrupted a hardirq
82 	 * handler) we can't do that and just have to keep using the
83 	 * current stack (which is the irq stack already after all)
84 	 */
85 	if (unlikely(curstk == irqstk))
86 		return 0;
87 
88 	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
89 
90 	/* Save the next esp at the bottom of the stack */
91 	prev_esp = (u32 *)irqstk;
92 	*prev_esp = current_stack_pointer();
93 
94 	if (unlikely(overflow))
95 		call_on_stack(print_stack_overflow, isp);
96 
97 	asm volatile("xchgl	%%ebx,%%esp	\n"
98 		     "call	*%%edi		\n"
99 		     "movl	%%ebx,%%esp	\n"
100 		     : "=a" (arg1), "=b" (isp)
101 		     :  "0" (desc),   "1" (isp),
102 			"D" (desc->handle_irq)
103 		     : "memory", "cc", "ecx");
104 	return 1;
105 }
106 
107 /*
108  * allocate per-cpu stacks for hardirq and for softirq processing
109  */
110 void irq_ctx_init(int cpu)
111 {
112 	struct irq_stack *irqstk;
113 
114 	if (per_cpu(hardirq_stack, cpu))
115 		return;
116 
117 	irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
118 					       THREADINFO_GFP,
119 					       THREAD_SIZE_ORDER));
120 	per_cpu(hardirq_stack, cpu) = irqstk;
121 
122 	irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
123 					       THREADINFO_GFP,
124 					       THREAD_SIZE_ORDER));
125 	per_cpu(softirq_stack, cpu) = irqstk;
126 
127 	printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
128 	       cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
129 }
130 
131 void do_softirq_own_stack(void)
132 {
133 	struct irq_stack *irqstk;
134 	u32 *isp, *prev_esp;
135 
136 	irqstk = __this_cpu_read(softirq_stack);
137 
138 	/* build the stack frame on the softirq stack */
139 	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
140 
141 	/* Push the previous esp onto the stack */
142 	prev_esp = (u32 *)irqstk;
143 	*prev_esp = current_stack_pointer();
144 
145 	call_on_stack(__do_softirq, isp);
146 }
147 
148 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
149 {
150 	int overflow = check_stack_overflow();
151 
152 	if (IS_ERR_OR_NULL(desc))
153 		return false;
154 
155 	if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
156 		if (unlikely(overflow))
157 			print_stack_overflow();
158 		generic_handle_irq_desc(desc);
159 	}
160 
161 	return true;
162 }
163