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Linux/arch/x86/kernel/irq_32.c

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

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