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
24DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
25EXPORT_PER_CPU_SYMBOL(irq_stat);
26
27DEFINE_PER_CPU(struct pt_regs *, irq_regs);
28EXPORT_PER_CPU_SYMBOL(irq_regs);
29
30#ifdef CONFIG_DEBUG_STACKOVERFLOW
31
32int sysctl_panic_on_stackoverflow __read_mostly;
33
34/* Debugging check for stack overflow: is there less than 1KB free? */
35static int check_stack_overflow(void)
36{
37	long sp;
38
39	__asm__ __volatile__("andl %%esp,%0" :
40			     "=r" (sp) : "0" (THREAD_SIZE - 1));
41
42	return sp < (sizeof(struct thread_info) + STACK_WARN);
43}
44
45static void print_stack_overflow(void)
46{
47	printk(KERN_WARNING "low stack detected by irq handler\n");
48	dump_stack();
49	if (sysctl_panic_on_stackoverflow)
50		panic("low stack detected by irq handler - check messages\n");
51}
52
53#else
54static inline int check_stack_overflow(void) { return 0; }
55static inline void print_stack_overflow(void) { }
56#endif
57
58DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
59DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
60
61static void call_on_stack(void *func, void *stack)
62{
63	asm volatile("xchgl	%%ebx,%%esp	\n"
64		     "call	*%%edi		\n"
65		     "movl	%%ebx,%%esp	\n"
66		     : "=b" (stack)
67		     : "0" (stack),
68		       "D"(func)
69		     : "memory", "cc", "edx", "ecx", "eax");
70}
71
72static inline void *current_stack(void)
73{
74	return (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
75}
76
77static inline int
78execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
79{
80	struct irq_stack *curstk, *irqstk;
81	u32 *isp, *prev_esp, arg1, arg2;
82
83	curstk = (struct irq_stack *) current_stack();
84	irqstk = __this_cpu_read(hardirq_stack);
85
86	/*
87	 * this is where we switch to the IRQ stack. However, if we are
88	 * already using the IRQ stack (because we interrupted a hardirq
89	 * handler) we can't do that and just have to keep using the
90	 * current stack (which is the irq stack already after all)
91	 */
92	if (unlikely(curstk == irqstk))
93		return 0;
94
95	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
96
97	/* Save the next esp at the bottom of the stack */
98	prev_esp = (u32 *)irqstk;
99	*prev_esp = current_stack_pointer();
100
101	if (unlikely(overflow))
102		call_on_stack(print_stack_overflow, isp);
103
104	asm volatile("xchgl	%%ebx,%%esp	\n"
105		     "call	*%%edi		\n"
106		     "movl	%%ebx,%%esp	\n"
107		     : "=a" (arg1), "=d" (arg2), "=b" (isp)
108		     :  "0" (irq),   "1" (desc),  "2" (isp),
109			"D" (desc->handle_irq)
110		     : "memory", "cc", "ecx");
111	return 1;
112}
113
114/*
115 * allocate per-cpu stacks for hardirq and for softirq processing
116 */
117void irq_ctx_init(int cpu)
118{
119	struct irq_stack *irqstk;
120
121	if (per_cpu(hardirq_stack, cpu))
122		return;
123
124	irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
125					       THREADINFO_GFP,
126					       THREAD_SIZE_ORDER));
127	per_cpu(hardirq_stack, cpu) = irqstk;
128
129	irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
130					       THREADINFO_GFP,
131					       THREAD_SIZE_ORDER));
132	per_cpu(softirq_stack, cpu) = irqstk;
133
134	printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
135	       cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
136}
137
138void do_softirq_own_stack(void)
139{
140	struct thread_info *curstk;
141	struct irq_stack *irqstk;
142	u32 *isp, *prev_esp;
143
144	curstk = current_stack();
145	irqstk = __this_cpu_read(softirq_stack);
146
147	/* build the stack frame on the softirq stack */
148	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
149
150	/* Push the previous esp onto the stack */
151	prev_esp = (u32 *)irqstk;
152	*prev_esp = current_stack_pointer();
153
154	call_on_stack(__do_softirq, isp);
155}
156
157bool handle_irq(unsigned irq, struct pt_regs *regs)
158{
159	struct irq_desc *desc;
160	int overflow;
161
162	overflow = check_stack_overflow();
163
164	desc = irq_to_desc(irq);
165	if (unlikely(!desc))
166		return false;
167
168	if (user_mode(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
169		if (unlikely(overflow))
170			print_stack_overflow();
171		desc->handle_irq(irq, desc);
172	}
173
174	return true;
175}
176