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60a5317ff0
Impact: stack protector for x86_32 Implement stack protector for x86_32. GDT entry 28 is used for it. It's set to point to stack_canary-20 and have the length of 24 bytes. CONFIG_CC_STACKPROTECTOR turns off CONFIG_X86_32_LAZY_GS and sets %gs to the stack canary segment on entry. As %gs is otherwise unused by the kernel, the canary can be anywhere. It's defined as a percpu variable. x86_32 exception handlers take register frame on stack directly as struct pt_regs. With -fstack-protector turned on, gcc copies the whole structure after the stack canary and (of course) doesn't copy back on return thus losing all changed. For now, -fno-stack-protector is added to all files which contain those functions. We definitely need something better. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
217 lines
6.1 KiB
C
217 lines
6.1 KiB
C
#ifndef _ASM_X86_SEGMENT_H
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#define _ASM_X86_SEGMENT_H
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/* Constructor for a conventional segment GDT (or LDT) entry */
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/* This is a macro so it can be used in initializers */
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#define GDT_ENTRY(flags, base, limit) \
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((((base) & 0xff000000ULL) << (56-24)) | \
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(((flags) & 0x0000f0ffULL) << 40) | \
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(((limit) & 0x000f0000ULL) << (48-16)) | \
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(((base) & 0x00ffffffULL) << 16) | \
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(((limit) & 0x0000ffffULL)))
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/* Simple and small GDT entries for booting only */
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#define GDT_ENTRY_BOOT_CS 2
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#define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8)
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#define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1)
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#define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
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#define GDT_ENTRY_BOOT_TSS (GDT_ENTRY_BOOT_CS + 2)
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#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS * 8)
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#ifdef CONFIG_X86_32
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/*
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* The layout of the per-CPU GDT under Linux:
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*
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* 0 - null
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* 1 - reserved
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* 2 - reserved
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* 3 - reserved
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*
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* 4 - unused <==== new cacheline
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* 5 - unused
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*
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* ------- start of TLS (Thread-Local Storage) segments:
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*
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* 6 - TLS segment #1 [ glibc's TLS segment ]
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* 7 - TLS segment #2 [ Wine's %fs Win32 segment ]
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* 8 - TLS segment #3
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* 9 - reserved
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* 10 - reserved
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* 11 - reserved
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*
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* ------- start of kernel segments:
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*
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* 12 - kernel code segment <==== new cacheline
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* 13 - kernel data segment
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* 14 - default user CS
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* 15 - default user DS
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* 16 - TSS
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* 17 - LDT
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* 18 - PNPBIOS support (16->32 gate)
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* 19 - PNPBIOS support
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* 20 - PNPBIOS support
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* 21 - PNPBIOS support
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* 22 - PNPBIOS support
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* 23 - APM BIOS support
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* 24 - APM BIOS support
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* 25 - APM BIOS support
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*
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* 26 - ESPFIX small SS
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* 27 - per-cpu [ offset to per-cpu data area ]
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* 28 - stack_canary-20 [ for stack protector ]
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* 29 - unused
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* 30 - unused
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* 31 - TSS for double fault handler
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*/
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#define GDT_ENTRY_TLS_MIN 6
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#define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
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#define GDT_ENTRY_DEFAULT_USER_CS 14
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#define GDT_ENTRY_DEFAULT_USER_DS 15
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#define GDT_ENTRY_KERNEL_BASE 12
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#define GDT_ENTRY_KERNEL_CS (GDT_ENTRY_KERNEL_BASE + 0)
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#define GDT_ENTRY_KERNEL_DS (GDT_ENTRY_KERNEL_BASE + 1)
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#define GDT_ENTRY_TSS (GDT_ENTRY_KERNEL_BASE + 4)
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#define GDT_ENTRY_LDT (GDT_ENTRY_KERNEL_BASE + 5)
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#define GDT_ENTRY_PNPBIOS_BASE (GDT_ENTRY_KERNEL_BASE + 6)
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#define GDT_ENTRY_APMBIOS_BASE (GDT_ENTRY_KERNEL_BASE + 11)
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#define GDT_ENTRY_ESPFIX_SS (GDT_ENTRY_KERNEL_BASE + 14)
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#define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS * 8)
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#define GDT_ENTRY_PERCPU (GDT_ENTRY_KERNEL_BASE + 15)
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#ifdef CONFIG_SMP
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#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8)
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#else
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#define __KERNEL_PERCPU 0
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#endif
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#define GDT_ENTRY_STACK_CANARY (GDT_ENTRY_KERNEL_BASE + 16)
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#ifdef CONFIG_CC_STACKPROTECTOR
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#define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY * 8)
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#else
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#define __KERNEL_STACK_CANARY 0
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#endif
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#define GDT_ENTRY_DOUBLEFAULT_TSS 31
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/*
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* The GDT has 32 entries
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*/
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#define GDT_ENTRIES 32
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/* The PnP BIOS entries in the GDT */
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#define GDT_ENTRY_PNPBIOS_CS32 (GDT_ENTRY_PNPBIOS_BASE + 0)
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#define GDT_ENTRY_PNPBIOS_CS16 (GDT_ENTRY_PNPBIOS_BASE + 1)
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#define GDT_ENTRY_PNPBIOS_DS (GDT_ENTRY_PNPBIOS_BASE + 2)
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#define GDT_ENTRY_PNPBIOS_TS1 (GDT_ENTRY_PNPBIOS_BASE + 3)
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#define GDT_ENTRY_PNPBIOS_TS2 (GDT_ENTRY_PNPBIOS_BASE + 4)
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/* The PnP BIOS selectors */
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#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32 * 8) /* segment for calling fn */
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#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16 * 8) /* code segment for BIOS */
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#define PNP_DS (GDT_ENTRY_PNPBIOS_DS * 8) /* data segment for BIOS */
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#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1 * 8) /* transfer data segment */
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#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2 * 8) /* another data segment */
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/* Bottom two bits of selector give the ring privilege level */
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#define SEGMENT_RPL_MASK 0x3
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/* Bit 2 is table indicator (LDT/GDT) */
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#define SEGMENT_TI_MASK 0x4
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/* User mode is privilege level 3 */
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#define USER_RPL 0x3
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/* LDT segment has TI set, GDT has it cleared */
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#define SEGMENT_LDT 0x4
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#define SEGMENT_GDT 0x0
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/*
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* Matching rules for certain types of segments.
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*/
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/* Matches PNP_CS32 and PNP_CS16 (they must be consecutive) */
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#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == GDT_ENTRY_PNPBIOS_BASE * 8)
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#else
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#include <asm/cache.h>
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#define GDT_ENTRY_KERNEL32_CS 1
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#define GDT_ENTRY_KERNEL_CS 2
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#define GDT_ENTRY_KERNEL_DS 3
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#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS * 8)
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/*
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* we cannot use the same code segment descriptor for user and kernel
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* -- not even in the long flat mode, because of different DPL /kkeil
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* The segment offset needs to contain a RPL. Grr. -AK
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* GDT layout to get 64bit syscall right (sysret hardcodes gdt offsets)
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*/
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#define GDT_ENTRY_DEFAULT_USER32_CS 4
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#define GDT_ENTRY_DEFAULT_USER_DS 5
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#define GDT_ENTRY_DEFAULT_USER_CS 6
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#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS * 8 + 3)
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#define __USER32_DS __USER_DS
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#define GDT_ENTRY_TSS 8 /* needs two entries */
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#define GDT_ENTRY_LDT 10 /* needs two entries */
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#define GDT_ENTRY_TLS_MIN 12
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#define GDT_ENTRY_TLS_MAX 14
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#define GDT_ENTRY_PER_CPU 15 /* Abused to load per CPU data from limit */
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#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU * 8 + 3)
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/* TLS indexes for 64bit - hardcoded in arch_prctl */
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#define FS_TLS 0
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#define GS_TLS 1
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#define GS_TLS_SEL ((GDT_ENTRY_TLS_MIN+GS_TLS)*8 + 3)
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#define FS_TLS_SEL ((GDT_ENTRY_TLS_MIN+FS_TLS)*8 + 3)
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#define GDT_ENTRIES 16
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#endif
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#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS * 8)
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#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS * 8)
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#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS* 8 + 3)
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#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS* 8 + 3)
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#ifndef CONFIG_PARAVIRT
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#define get_kernel_rpl() 0
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#endif
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/* User mode is privilege level 3 */
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#define USER_RPL 0x3
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/* LDT segment has TI set, GDT has it cleared */
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#define SEGMENT_LDT 0x4
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#define SEGMENT_GDT 0x0
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/* Bottom two bits of selector give the ring privilege level */
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#define SEGMENT_RPL_MASK 0x3
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/* Bit 2 is table indicator (LDT/GDT) */
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#define SEGMENT_TI_MASK 0x4
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#define IDT_ENTRIES 256
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#define NUM_EXCEPTION_VECTORS 32
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#define GDT_SIZE (GDT_ENTRIES * 8)
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#define GDT_ENTRY_TLS_ENTRIES 3
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#define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES * 8)
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#ifdef __KERNEL__
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#ifndef __ASSEMBLY__
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extern const char early_idt_handlers[NUM_EXCEPTION_VECTORS][10];
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#endif
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#endif
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#endif /* _ASM_X86_SEGMENT_H */
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