1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *	Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
4  *
5  * This file contains the lowest level x86-specific interrupt
6  * entry, irq-stacks and irq statistics code. All the remaining
7  * irq logic is done by the generic kernel/irq/ code and
8  * by the x86-specific irq controller code. (e.g. i8259.c and
9  * io_apic.c.)
10  */
11 
12 #include <linux/seq_file.h>
13 #include <linux/interrupt.h>
14 #include <linux/irq.h>
15 #include <linux/kernel_stat.h>
16 #include <linux/notifier.h>
17 #include <linux/cpu.h>
18 #include <linux/delay.h>
19 #include <linux/uaccess.h>
20 #include <linux/percpu.h>
21 #include <linux/mm.h>
22 
23 #include <asm/apic.h>
24 #include <asm/nospec-branch.h>
25 #include <asm/softirq_stack.h>
26 
27 #ifdef CONFIG_DEBUG_STACKOVERFLOW
28 
29 int sysctl_panic_on_stackoverflow __read_mostly;
30 
31 /* Debugging check for stack overflow: is there less than 1KB free? */
check_stack_overflow(void)32 static bool check_stack_overflow(void)
33 {
34 	unsigned long sp = current_stack_pointer & (THREAD_SIZE - 1);
35 
36 	return sp < (sizeof(struct thread_info) + STACK_WARN);
37 }
38 
print_stack_overflow(void)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
check_stack_overflow(void)48 static inline bool check_stack_overflow(void) { return false; }
print_stack_overflow(void)49 static inline void print_stack_overflow(void) { }
50 #endif
51 
52 DEFINE_PER_CPU_CACHE_HOT(struct irq_stack *, softirq_stack_ptr);
53 
call_on_stack(void * func,void * stack)54 static void call_on_stack(void *func, void *stack)
55 {
56 	asm volatile("xchgl %[sp], %%esp\n"
57 		     CALL_NOSPEC
58 		     "movl %[sp], %%esp"
59 		     : [sp] "+b" (stack)
60 		     : [thunk_target] "D" (func)
61 		     : "memory", "cc", "edx", "ecx", "eax");
62 }
63 
current_stack(void)64 static inline void *current_stack(void)
65 {
66 	return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
67 }
68 
execute_on_irq_stack(bool overflow,struct irq_desc * desc)69 static inline bool execute_on_irq_stack(bool overflow, struct irq_desc *desc)
70 {
71 	struct irq_stack *curstk, *irqstk;
72 	u32 *isp, *prev_esp;
73 
74 	curstk = (struct irq_stack *) current_stack();
75 	irqstk = __this_cpu_read(hardirq_stack_ptr);
76 
77 	/*
78 	 * this is where we switch to the IRQ stack. However, if we are
79 	 * already using the IRQ stack (because we interrupted a hardirq
80 	 * handler) we can't do that and just have to keep using the
81 	 * current stack (which is the irq stack already after all)
82 	 */
83 	if (unlikely(curstk == irqstk))
84 		return false;
85 
86 	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
87 
88 	/* Save the next esp at the bottom of the stack */
89 	prev_esp = (u32 *)irqstk;
90 	*prev_esp = current_stack_pointer;
91 
92 	if (unlikely(overflow))
93 		call_on_stack(print_stack_overflow, isp);
94 
95 	asm volatile("xchgl %[sp], %%esp\n"
96 		     CALL_NOSPEC
97 		     "movl %[sp], %%esp"
98 		     : "+a" (desc), [sp] "+b" (isp)
99 		     : [thunk_target] "D" (desc->handle_irq)
100 		     : "memory", "cc", "edx", "ecx");
101 	return true;
102 }
103 
104 /*
105  * Allocate per-cpu stacks for hardirq and softirq processing
106  */
irq_init_percpu_irqstack(unsigned int cpu)107 int irq_init_percpu_irqstack(unsigned int cpu)
108 {
109 	int node = cpu_to_node(cpu);
110 	struct page *ph, *ps;
111 
112 	if (per_cpu(hardirq_stack_ptr, cpu))
113 		return 0;
114 
115 	ph = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
116 	if (!ph)
117 		return -ENOMEM;
118 	ps = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
119 	if (!ps) {
120 		__free_pages(ph, THREAD_SIZE_ORDER);
121 		return -ENOMEM;
122 	}
123 
124 	per_cpu(hardirq_stack_ptr, cpu) = page_address(ph);
125 	per_cpu(softirq_stack_ptr, cpu) = page_address(ps);
126 	return 0;
127 }
128 
129 #ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
do_softirq_own_stack(void)130 void do_softirq_own_stack(void)
131 {
132 	struct irq_stack *irqstk;
133 	u32 *isp, *prev_esp;
134 
135 	irqstk = __this_cpu_read(softirq_stack_ptr);
136 
137 	/* build the stack frame on the softirq stack */
138 	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
139 
140 	/* Push the previous esp onto the stack */
141 	prev_esp = (u32 *)irqstk;
142 	*prev_esp = current_stack_pointer;
143 
144 	call_on_stack(__do_softirq, isp);
145 }
146 #endif
147 
__handle_irq(struct irq_desc * desc,struct pt_regs * regs)148 void __handle_irq(struct irq_desc *desc, struct pt_regs *regs)
149 {
150 	bool overflow = check_stack_overflow();
151 
152 	if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
153 		if (unlikely(overflow))
154 			print_stack_overflow();
155 		generic_handle_irq_desc(desc);
156 	}
157 }
158