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 int check_stack_overflow(void)
33 {
34 long sp;
35
36 __asm__ __volatile__("andl %%esp,%0" :
37 "=r" (sp) : "0" (THREAD_SIZE - 1));
38
39 return sp < (sizeof(struct thread_info) + STACK_WARN);
40 }
41
print_stack_overflow(void)42 static void print_stack_overflow(void)
43 {
44 printk(KERN_WARNING "low stack detected by irq handler\n");
45 dump_stack();
46 if (sysctl_panic_on_stackoverflow)
47 panic("low stack detected by irq handler - check messages\n");
48 }
49
50 #else
check_stack_overflow(void)51 static inline int check_stack_overflow(void) { return 0; }
print_stack_overflow(void)52 static inline void print_stack_overflow(void) { }
53 #endif
54
55 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack_ptr);
56 DEFINE_PER_CPU(struct irq_stack *, softirq_stack_ptr);
57
call_on_stack(void * func,void * stack)58 static void call_on_stack(void *func, void *stack)
59 {
60 asm volatile("xchgl %%ebx,%%esp \n"
61 CALL_NOSPEC
62 "movl %%ebx,%%esp \n"
63 : "=b" (stack)
64 : "0" (stack),
65 [thunk_target] "D"(func)
66 : "memory", "cc", "edx", "ecx", "eax");
67 }
68
current_stack(void)69 static inline void *current_stack(void)
70 {
71 return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
72 }
73
execute_on_irq_stack(int overflow,struct irq_desc * desc)74 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
75 {
76 struct irq_stack *curstk, *irqstk;
77 u32 *isp, *prev_esp, arg1;
78
79 curstk = (struct irq_stack *) current_stack();
80 irqstk = __this_cpu_read(hardirq_stack_ptr);
81
82 /*
83 * this is where we switch to the IRQ stack. However, if we are
84 * already using the IRQ stack (because we interrupted a hardirq
85 * handler) we can't do that and just have to keep using the
86 * current stack (which is the irq stack already after all)
87 */
88 if (unlikely(curstk == irqstk))
89 return 0;
90
91 isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
92
93 /* Save the next esp at the bottom of the stack */
94 prev_esp = (u32 *)irqstk;
95 *prev_esp = current_stack_pointer;
96
97 if (unlikely(overflow))
98 call_on_stack(print_stack_overflow, isp);
99
100 asm volatile("xchgl %%ebx,%%esp \n"
101 CALL_NOSPEC
102 "movl %%ebx,%%esp \n"
103 : "=a" (arg1), "=b" (isp)
104 : "0" (desc), "1" (isp),
105 [thunk_target] "D" (desc->handle_irq)
106 : "memory", "cc", "ecx");
107 return 1;
108 }
109
110 /*
111 * Allocate per-cpu stacks for hardirq and softirq processing
112 */
irq_init_percpu_irqstack(unsigned int cpu)113 int irq_init_percpu_irqstack(unsigned int cpu)
114 {
115 int node = cpu_to_node(cpu);
116 struct page *ph, *ps;
117
118 if (per_cpu(hardirq_stack_ptr, cpu))
119 return 0;
120
121 ph = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
122 if (!ph)
123 return -ENOMEM;
124 ps = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
125 if (!ps) {
126 __free_pages(ph, THREAD_SIZE_ORDER);
127 return -ENOMEM;
128 }
129
130 per_cpu(hardirq_stack_ptr, cpu) = page_address(ph);
131 per_cpu(softirq_stack_ptr, cpu) = page_address(ps);
132 return 0;
133 }
134
do_softirq_own_stack(void)135 void do_softirq_own_stack(void)
136 {
137 struct irq_stack *irqstk;
138 u32 *isp, *prev_esp;
139
140 irqstk = __this_cpu_read(softirq_stack_ptr);
141
142 /* build the stack frame on the softirq stack */
143 isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
144
145 /* Push the previous esp onto the stack */
146 prev_esp = (u32 *)irqstk;
147 *prev_esp = current_stack_pointer;
148
149 call_on_stack(__do_softirq, isp);
150 }
151
__handle_irq(struct irq_desc * desc,struct pt_regs * regs)152 void __handle_irq(struct irq_desc *desc, struct pt_regs *regs)
153 {
154 int overflow = check_stack_overflow();
155
156 if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
157 if (unlikely(overflow))
158 print_stack_overflow();
159 generic_handle_irq_desc(desc);
160 }
161 }
162