v4.19.13 snapshot.
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
new file mode 100644
index 0000000..95600a9
--- /dev/null
+++ b/arch/x86/kernel/irq_32.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
+ *
+ * This file contains the lowest level x86-specific interrupt
+ * entry, irq-stacks and irq statistics code. All the remaining
+ * irq logic is done by the generic kernel/irq/ code and
+ * by the x86-specific irq controller code. (e.g. i8259.c and
+ * io_apic.c.)
+ */
+
+#include <linux/seq_file.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel_stat.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/uaccess.h>
+#include <linux/percpu.h>
+#include <linux/mm.h>
+
+#include <asm/apic.h>
+#include <asm/nospec-branch.h>
+
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+
+int sysctl_panic_on_stackoverflow __read_mostly;
+
+/* Debugging check for stack overflow: is there less than 1KB free? */
+static int check_stack_overflow(void)
+{
+ long sp;
+
+ __asm__ __volatile__("andl %%esp,%0" :
+ "=r" (sp) : "0" (THREAD_SIZE - 1));
+
+ return sp < (sizeof(struct thread_info) + STACK_WARN);
+}
+
+static void print_stack_overflow(void)
+{
+ printk(KERN_WARNING "low stack detected by irq handler\n");
+ dump_stack();
+ if (sysctl_panic_on_stackoverflow)
+ panic("low stack detected by irq handler - check messages\n");
+}
+
+#else
+static inline int check_stack_overflow(void) { return 0; }
+static inline void print_stack_overflow(void) { }
+#endif
+
+DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
+DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
+
+static void call_on_stack(void *func, void *stack)
+{
+ asm volatile("xchgl %%ebx,%%esp \n"
+ CALL_NOSPEC
+ "movl %%ebx,%%esp \n"
+ : "=b" (stack)
+ : "0" (stack),
+ [thunk_target] "D"(func)
+ : "memory", "cc", "edx", "ecx", "eax");
+}
+
+static inline void *current_stack(void)
+{
+ return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
+}
+
+static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
+{
+ struct irq_stack *curstk, *irqstk;
+ u32 *isp, *prev_esp, arg1;
+
+ curstk = (struct irq_stack *) current_stack();
+ irqstk = __this_cpu_read(hardirq_stack);
+
+ /*
+ * this is where we switch to the IRQ stack. However, if we are
+ * already using the IRQ stack (because we interrupted a hardirq
+ * handler) we can't do that and just have to keep using the
+ * current stack (which is the irq stack already after all)
+ */
+ if (unlikely(curstk == irqstk))
+ return 0;
+
+ isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
+
+ /* Save the next esp at the bottom of the stack */
+ prev_esp = (u32 *)irqstk;
+ *prev_esp = current_stack_pointer;
+
+ if (unlikely(overflow))
+ call_on_stack(print_stack_overflow, isp);
+
+ asm volatile("xchgl %%ebx,%%esp \n"
+ CALL_NOSPEC
+ "movl %%ebx,%%esp \n"
+ : "=a" (arg1), "=b" (isp)
+ : "0" (desc), "1" (isp),
+ [thunk_target] "D" (desc->handle_irq)
+ : "memory", "cc", "ecx");
+ return 1;
+}
+
+/*
+ * allocate per-cpu stacks for hardirq and for softirq processing
+ */
+void irq_ctx_init(int cpu)
+{
+ struct irq_stack *irqstk;
+
+ if (per_cpu(hardirq_stack, cpu))
+ return;
+
+ irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
+ THREADINFO_GFP,
+ THREAD_SIZE_ORDER));
+ per_cpu(hardirq_stack, cpu) = irqstk;
+
+ irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
+ THREADINFO_GFP,
+ THREAD_SIZE_ORDER));
+ per_cpu(softirq_stack, cpu) = irqstk;
+
+ printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
+ cpu, per_cpu(hardirq_stack, cpu), per_cpu(softirq_stack, cpu));
+}
+
+void do_softirq_own_stack(void)
+{
+ struct irq_stack *irqstk;
+ u32 *isp, *prev_esp;
+
+ irqstk = __this_cpu_read(softirq_stack);
+
+ /* build the stack frame on the softirq stack */
+ isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
+
+ /* Push the previous esp onto the stack */
+ prev_esp = (u32 *)irqstk;
+ *prev_esp = current_stack_pointer;
+
+ call_on_stack(__do_softirq, isp);
+}
+
+bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
+{
+ int overflow = check_stack_overflow();
+
+ if (IS_ERR_OR_NULL(desc))
+ return false;
+
+ if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
+ if (unlikely(overflow))
+ print_stack_overflow();
+ generic_handle_irq_desc(desc);
+ }
+
+ return true;
+}