GNU Linux-libre 4.14.266-gnu1
[releases.git] / arch / x86 / kernel / irq_32.c
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
26 #ifdef CONFIG_DEBUG_STACKOVERFLOW
27
28 int sysctl_panic_on_stackoverflow __read_mostly;
29
30 /* Debugging check for stack overflow: is there less than 1KB free? */
31 static int check_stack_overflow(void)
32 {
33         long sp;
34
35         __asm__ __volatile__("andl %%esp,%0" :
36                              "=r" (sp) : "0" (THREAD_SIZE - 1));
37
38         return sp < (sizeof(struct thread_info) + STACK_WARN);
39 }
40
41 static void print_stack_overflow(void)
42 {
43         printk(KERN_WARNING "low stack detected by irq handler\n");
44         dump_stack();
45         if (sysctl_panic_on_stackoverflow)
46                 panic("low stack detected by irq handler - check messages\n");
47 }
48
49 #else
50 static inline int check_stack_overflow(void) { return 0; }
51 static inline void print_stack_overflow(void) { }
52 #endif
53
54 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
55 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
56
57 static void call_on_stack(void *func, void *stack)
58 {
59         asm volatile("xchgl     %%ebx,%%esp     \n"
60                      CALL_NOSPEC
61                      "movl      %%ebx,%%esp     \n"
62                      : "=b" (stack)
63                      : "0" (stack),
64                        [thunk_target] "D"(func)
65                      : "memory", "cc", "edx", "ecx", "eax");
66 }
67
68 static inline void *current_stack(void)
69 {
70         return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
71 }
72
73 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
74 {
75         struct irq_stack *curstk, *irqstk;
76         u32 *isp, *prev_esp, arg1;
77
78         curstk = (struct irq_stack *) current_stack();
79         irqstk = __this_cpu_read(hardirq_stack);
80
81         /*
82          * this is where we switch to the IRQ stack. However, if we are
83          * already using the IRQ stack (because we interrupted a hardirq
84          * handler) we can't do that and just have to keep using the
85          * current stack (which is the irq stack already after all)
86          */
87         if (unlikely(curstk == irqstk))
88                 return 0;
89
90         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
91
92         /* Save the next esp at the bottom of the stack */
93         prev_esp = (u32 *)irqstk;
94         *prev_esp = current_stack_pointer;
95
96         if (unlikely(overflow))
97                 call_on_stack(print_stack_overflow, isp);
98
99         asm volatile("xchgl     %%ebx,%%esp     \n"
100                      CALL_NOSPEC
101                      "movl      %%ebx,%%esp     \n"
102                      : "=a" (arg1), "=b" (isp)
103                      :  "0" (desc),   "1" (isp),
104                         [thunk_target] "D" (desc->handle_irq)
105                      : "memory", "cc", "ecx");
106         return 1;
107 }
108
109 /*
110  * allocate per-cpu stacks for hardirq and for softirq processing
111  */
112 void irq_ctx_init(int cpu)
113 {
114         struct irq_stack *irqstk;
115
116         if (per_cpu(hardirq_stack, cpu))
117                 return;
118
119         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
120                                                THREADINFO_GFP,
121                                                THREAD_SIZE_ORDER));
122         per_cpu(hardirq_stack, cpu) = irqstk;
123
124         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
125                                                THREADINFO_GFP,
126                                                THREAD_SIZE_ORDER));
127         per_cpu(softirq_stack, cpu) = irqstk;
128
129         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
130                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
131 }
132
133 void do_softirq_own_stack(void)
134 {
135         struct irq_stack *irqstk;
136         u32 *isp, *prev_esp;
137
138         irqstk = __this_cpu_read(softirq_stack);
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
150 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
151 {
152         int overflow = check_stack_overflow();
153
154         if (IS_ERR_OR_NULL(desc))
155                 return false;
156
157         if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
158                 if (unlikely(overflow))
159                         print_stack_overflow();
160                 generic_handle_irq_desc(desc);
161         }
162
163         return true;
164 }