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https://github.com/Fishwaldo/Star64_linux.git
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ecc7e37d4d
There is no requirement to update the TSS I/O bitmap when a thread using it is scheduled out and the incoming thread does not use it. For the permission check based on the TSS I/O bitmap the CPU calculates the memory location of the I/O bitmap by the address of the TSS and the io_bitmap_base member of the tss_struct. The easiest way to invalidate the I/O bitmap is to switch the offset to an address outside of the TSS limit. If an I/O instruction is issued from user space the TSS limit causes #GP to be raised in the same was as valid I/O bitmap with all bits set to 1 would do. This removes the extra work when an I/O bitmap using task is scheduled out and puts the burden on the rare I/O bitmap users when they are scheduled in. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
83 lines
2 KiB
C
83 lines
2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/init_task.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <asm/pgtable.h>
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#include <asm/processor.h>
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#include <asm/desc.h>
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#ifdef CONFIG_X86_32
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#define DOUBLEFAULT_STACKSIZE (1024)
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static unsigned long doublefault_stack[DOUBLEFAULT_STACKSIZE];
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#define STACK_START (unsigned long)(doublefault_stack+DOUBLEFAULT_STACKSIZE)
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#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)
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static void doublefault_fn(void)
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{
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struct desc_ptr gdt_desc = {0, 0};
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unsigned long gdt, tss;
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native_store_gdt(&gdt_desc);
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gdt = gdt_desc.address;
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printk(KERN_EMERG "PANIC: double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size);
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if (ptr_ok(gdt)) {
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gdt += GDT_ENTRY_TSS << 3;
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tss = get_desc_base((struct desc_struct *)gdt);
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printk(KERN_EMERG "double fault, tss at %08lx\n", tss);
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if (ptr_ok(tss)) {
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struct x86_hw_tss *t = (struct x86_hw_tss *)tss;
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printk(KERN_EMERG "eip = %08lx, esp = %08lx\n",
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t->ip, t->sp);
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printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
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t->ax, t->bx, t->cx, t->dx);
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printk(KERN_EMERG "esi = %08lx, edi = %08lx\n",
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t->si, t->di);
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}
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}
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for (;;)
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cpu_relax();
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}
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struct x86_hw_tss doublefault_tss __cacheline_aligned = {
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.sp0 = STACK_START,
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.ss0 = __KERNEL_DS,
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.ldt = 0,
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.io_bitmap_base = IO_BITMAP_OFFSET_INVALID,
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.ip = (unsigned long) doublefault_fn,
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/* 0x2 bit is always set */
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.flags = X86_EFLAGS_SF | 0x2,
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.sp = STACK_START,
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.es = __USER_DS,
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.cs = __KERNEL_CS,
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.ss = __KERNEL_DS,
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.ds = __USER_DS,
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.fs = __KERNEL_PERCPU,
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.__cr3 = __pa_nodebug(swapper_pg_dir),
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};
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/* dummy for do_double_fault() call */
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void df_debug(struct pt_regs *regs, long error_code) {}
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#else /* !CONFIG_X86_32 */
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void df_debug(struct pt_regs *regs, long error_code)
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{
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pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
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show_regs(regs);
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panic("Machine halted.");
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}
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#endif
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