root/arch/x86/kernel/irq_32.c

DEFINITIONS

1. check_stack_overflow
2. print_stack_overflow
3. check_stack_overflow
4. print_stack_overflow
5. call_on_stack
6. current_stack
7. execute_on_irq_stack
8. irq_init_percpu_irqstack
9. do_softirq_own_stack
10. handle_irq

   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_ptr);
  55 DEFINE_PER_CPU(struct irq_stack *, softirq_stack_ptr);
  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_ptr);
  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 softirq processing
 111  */
 112 int irq_init_percpu_irqstack(unsigned int cpu)
 113 {
 114         int node = cpu_to_node(cpu);
 115         struct page *ph, *ps;
 116 
 117         if (per_cpu(hardirq_stack_ptr, cpu))
 118                 return 0;
 119 
 120         ph = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
 121         if (!ph)
 122                 return -ENOMEM;
 123         ps = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
 124         if (!ps) {
 125                 __free_pages(ph, THREAD_SIZE_ORDER);
 126                 return -ENOMEM;
 127         }
 128 
 129         per_cpu(hardirq_stack_ptr, cpu) = page_address(ph);
 130         per_cpu(softirq_stack_ptr, cpu) = page_address(ps);
 131         return 0;
 132 }
 133 
 134 void do_softirq_own_stack(void)
 135 {
 136         struct irq_stack *irqstk;
 137         u32 *isp, *prev_esp;
 138 
 139         irqstk = __this_cpu_read(softirq_stack_ptr);
 140 
 141         /* build the stack frame on the softirq stack */
 142         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 143 
 144         /* Push the previous esp onto the stack */
 145         prev_esp = (u32 *)irqstk;
 146         *prev_esp = current_stack_pointer;
 147 
 148         call_on_stack(__do_softirq, isp);
 149 }
 150 
 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 }