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133 lines
3.5 KiB
133 lines
3.5 KiB
// 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/processor.h> |
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#include <asm/desc.h> |
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#include <asm/traps.h> |
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#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM) |
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#define TSS(x) this_cpu_read(cpu_tss_rw.x86_tss.x) |
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static void set_df_gdt_entry(unsigned int cpu); |
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/* |
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* Called by double_fault with CR0.TS and EFLAGS.NT cleared. The CPU thinks |
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* we're running the doublefault task. Cannot return. |
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*/ |
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asmlinkage noinstr void __noreturn doublefault_shim(void) |
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{ |
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unsigned long cr2; |
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struct pt_regs regs; |
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BUILD_BUG_ON(sizeof(struct doublefault_stack) != PAGE_SIZE); |
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cr2 = native_read_cr2(); |
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/* Reset back to the normal kernel task. */ |
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force_reload_TR(); |
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set_df_gdt_entry(smp_processor_id()); |
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trace_hardirqs_off(); |
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/* |
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* Fill in pt_regs. A downside of doing this in C is that the unwinder |
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* won't see it (no ENCODE_FRAME_POINTER), so a nested stack dump |
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* won't successfully unwind to the source of the double fault. |
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* The main dump from exc_double_fault() is fine, though, since it |
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* uses these regs directly. |
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* |
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* If anyone ever cares, this could be moved to asm. |
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*/ |
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regs.ss = TSS(ss); |
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regs.__ssh = 0; |
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regs.sp = TSS(sp); |
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regs.flags = TSS(flags); |
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regs.cs = TSS(cs); |
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/* We won't go through the entry asm, so we can leave __csh as 0. */ |
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regs.__csh = 0; |
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regs.ip = TSS(ip); |
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regs.orig_ax = 0; |
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regs.gs = TSS(gs); |
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regs.__gsh = 0; |
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regs.fs = TSS(fs); |
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regs.__fsh = 0; |
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regs.es = TSS(es); |
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regs.__esh = 0; |
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regs.ds = TSS(ds); |
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regs.__dsh = 0; |
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regs.ax = TSS(ax); |
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regs.bp = TSS(bp); |
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regs.di = TSS(di); |
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regs.si = TSS(si); |
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regs.dx = TSS(dx); |
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regs.cx = TSS(cx); |
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regs.bx = TSS(bx); |
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exc_double_fault(®s, 0, cr2); |
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/* |
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* x86_32 does not save the original CR3 anywhere on a task switch. |
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* This means that, even if we wanted to return, we would need to find |
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* some way to reconstruct CR3. We could make a credible guess based |
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* on cpu_tlbstate, but that would be racy and would not account for |
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* PTI. |
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* |
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* Instead, don't bother. We can return through |
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* rewind_stack_do_exit() instead. |
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*/ |
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panic("cannot return from double fault\n"); |
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} |
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DEFINE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack) = { |
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.tss = { |
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/* |
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* No sp0 or ss0 -- we never run CPL != 0 with this TSS |
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* active. sp is filled in later. |
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*/ |
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.ldt = 0, |
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.io_bitmap_base = IO_BITMAP_OFFSET_INVALID, |
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.ip = (unsigned long) asm_exc_double_fault, |
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.flags = X86_EFLAGS_FIXED, |
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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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#ifndef CONFIG_X86_32_LAZY_GS |
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.gs = __KERNEL_STACK_CANARY, |
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#endif |
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.__cr3 = __pa_nodebug(swapper_pg_dir), |
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}, |
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}; |
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static void set_df_gdt_entry(unsigned int cpu) |
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{ |
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/* Set up doublefault TSS pointer in the GDT */ |
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__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, |
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&get_cpu_entry_area(cpu)->doublefault_stack.tss); |
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} |
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void doublefault_init_cpu_tss(void) |
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{ |
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unsigned int cpu = smp_processor_id(); |
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struct cpu_entry_area *cea = get_cpu_entry_area(cpu); |
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/* |
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* The linker isn't smart enough to initialize percpu variables that |
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* point to other places in percpu space. |
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*/ |
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this_cpu_write(doublefault_stack.tss.sp, |
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(unsigned long)&cea->doublefault_stack.stack + |
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sizeof(doublefault_stack.stack)); |
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set_df_gdt_entry(cpu); |
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}
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