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
call_on_stack(void * func,void * stack)55 static void call_on_stack(void *func, void *stack)
56 {
57 asm volatile("xchgl %%ebx,%%esp \n"
58 CALL_NOSPEC
59 "movl %%ebx,%%esp \n"
60 : "=b" (stack)
61 : "0" (stack),
62 [thunk_target] "D"(func)
63 : "memory", "cc", "edx", "ecx", "eax");
64 }
65
current_stack(void)66 static inline void *current_stack(void)
67 {
68 return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
69 }
70
execute_on_irq_stack(int overflow,struct irq_desc * desc)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(pcpu_hot.hardirq_stack_ptr);
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_NOSPEC
99 "movl %%ebx,%%esp \n"
100 : "=a" (arg1), "=b" (isp)
101 : "0" (desc), "1" (isp),
102 [thunk_target] "D" (desc->handle_irq)
103 : "memory", "cc", "ecx");
104 return 1;
105 }
106
107 /*
108 * Allocate per-cpu stacks for hardirq and softirq processing
109 */
irq_init_percpu_irqstack(unsigned int cpu)110 int irq_init_percpu_irqstack(unsigned int cpu)
111 {
112 int node = cpu_to_node(cpu);
113 struct page *ph, *ps;
114
115 if (per_cpu(pcpu_hot.hardirq_stack_ptr, cpu))
116 return 0;
117
118 ph = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
119 if (!ph)
120 return -ENOMEM;
121 ps = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
122 if (!ps) {
123 __free_pages(ph, THREAD_SIZE_ORDER);
124 return -ENOMEM;
125 }
126
127 per_cpu(pcpu_hot.hardirq_stack_ptr, cpu) = page_address(ph);
128 per_cpu(pcpu_hot.softirq_stack_ptr, cpu) = page_address(ps);
129 return 0;
130 }
131
132 #ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
do_softirq_own_stack(void)133 void do_softirq_own_stack(void)
134 {
135 struct irq_stack *irqstk;
136 u32 *isp, *prev_esp;
137
138 irqstk = __this_cpu_read(pcpu_hot.softirq_stack_ptr);
139
140 /* build the stack frame on the softirq stack */
141 isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
142
143 /* Push the previous esp onto the stack */
144 prev_esp = (u32 *)irqstk;
145 *prev_esp = current_stack_pointer;
146
147 call_on_stack(__do_softirq, isp);
148 }
149 #endif
150
__handle_irq(struct irq_desc * desc,struct pt_regs * regs)151 void __handle_irq(struct irq_desc *desc, struct pt_regs *regs)
152 {
153 int overflow = check_stack_overflow();
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