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x86/asm: Further improve segment.h readability
- extend/clarify explanations where necessary - move comments from macro values to before the macro, to make them more consistent, and to reduce preprocessor overhead - sort GDT index and selector values likewise by number - use consistent, modern kernel coding style across the file - capitalize consistently - use consistent vertical spacing - remove the unused get_limit() method (noticed by Andy Lutomirski) No change in code (verified with objdump -d): 64-bit defconfig+kvmconfig: 815a129bc1f80de6445c1d8ca5b97cad vmlinux.o.before.asm 815a129bc1f80de6445c1d8ca5b97cad vmlinux.o.after.asm 32-bit defconfig+kvmconfig: e659ef045159ddf41a0771b33a34aae5 vmlinux.o.before.asm e659ef045159ddf41a0771b33a34aae5 vmlinux.o.after.asm Acked-by: Andy Lutomirski <luto@amacapital.net> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Will Drewry <wad@chromium.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
parent
dca5b52ad7
commit
72d64cc769
@ -3,8 +3,10 @@
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#include <linux/const.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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/*
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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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*/
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#define GDT_ENTRY(flags, base, limit) \
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((((base) & _AC(0xff000000,ULL)) << (56-24)) | \
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(((flags) & _AC(0x0000f0ff,ULL)) << 40) | \
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@ -12,71 +14,78 @@
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(((base) & _AC(0x00ffffff,ULL)) << 16) | \
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(((limit) & _AC(0x0000ffff,ULL))))
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/* Simple and small GDT entries for booting only */
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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 GDT_ENTRY_BOOT_DS 3
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#define GDT_ENTRY_BOOT_TSS 4
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#define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8)
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#define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
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#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS * 8)
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#define __BOOT_CS (GDT_ENTRY_BOOT_CS*8)
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#define __BOOT_DS (GDT_ENTRY_BOOT_DS*8)
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#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS*8)
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#define SEGMENT_RPL_MASK 0x3 /*
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* Bottom two bits of selector give the ring
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* privilege level
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*/
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#define SEGMENT_TI_MASK 0x4 /* Bit 2 is table indicator (LDT/GDT) */
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#define USER_RPL 0x3 /* User mode is privilege level 3 */
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#define SEGMENT_LDT 0x4 /* LDT segment has TI set... */
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#define SEGMENT_GDT 0x0 /* ... GDT has it cleared */
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/*
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* Bottom two bits of selector give the ring
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* privilege level
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*/
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#define SEGMENT_RPL_MASK 0x3
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/* User mode is privilege level 3: */
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#define USER_RPL 0x3
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/* Bit 2 is Table Indicator (TI): selects between LDT or GDT */
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#define SEGMENT_TI_MASK 0x4
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/* LDT segment has TI set ... */
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#define SEGMENT_LDT 0x4
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/* ... GDT has it cleared */
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#define SEGMENT_GDT 0x0
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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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* 0 - null <=== cacheline #1
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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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* 4 - unused <=== cacheline #2
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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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* 8 - TLS segment #3 <=== cacheline #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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* 12 - kernel code segment <=== cacheline #4
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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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* 16 - TSS <=== cacheline #5
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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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* 20 - PNPBIOS support <=== cacheline #6
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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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* 24 - APM BIOS support <=== cacheline #7
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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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* 28 - stack_canary-20 [ for stack protector ] <=== cacheline #8
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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_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_KERNEL_CS 12
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#define GDT_ENTRY_KERNEL_DS 13
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@ -97,96 +106,134 @@
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#define GDT_ENTRY_DOUBLEFAULT_TSS 31
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/*
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* Number of entries in the GDT table:
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*/
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#define GDT_ENTRIES 32
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/*
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* Segment selector values corresponding to the above entries:
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*/
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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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#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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#define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8)
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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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/* segment for calling fn: */
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#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32*8)
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/* code segment for BIOS: */
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#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16*8)
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/* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
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#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32)
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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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#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32)
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/* data segment for BIOS: */
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#define PNP_DS (GDT_ENTRY_PNPBIOS_DS*8)
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/* transfer data segment: */
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#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1*8)
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/* another data segment: */
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#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2*8)
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#ifdef CONFIG_SMP
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#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8)
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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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#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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# define __KERNEL_PERCPU 0
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#endif
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#define GDT_ENTRIES 32
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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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#else /* 64-bit: */
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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 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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/*
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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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* GDT layout to get 64bit syscall/sysret right. sysret hardcodes selectors:
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* if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
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* if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
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* We cannot use the same code segment descriptor for user and kernel mode,
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* not even in long flat mode, because of different DPL.
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*
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* GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
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* selectors:
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*
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* if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
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* if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
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*
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* ss = STAR.SYSRET_CS+8 (in either case)
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*
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* thus USER_DS should be between 32-bit and 64-bit code selectors:
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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 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 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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/* Needs two entries */
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#define GDT_ENTRY_TSS 8
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/* Needs two entries */
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#define GDT_ENTRY_LDT 10
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#define GDT_ENTRY_PER_CPU 15 /* abused to load per CPU data from limit */
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#define GDT_ENTRY_TLS_MIN 12
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#define GDT_ENTRY_TLS_MAX 14
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/* Selectors need to also have a correct RPL (+3 thingy) */
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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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#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8)
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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 __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8+3)
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/* Abused to load per CPU data from limit */
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#define GDT_ENTRY_PER_CPU 15
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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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/*
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* Number of entries in the GDT table:
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*/
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#define GDT_ENTRIES 16
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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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/*
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* Segment selector values corresponding to the above entries:
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*
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* Note, selectors also need to have a correct RPL,
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* expressed with the +3 value for user-space selectors:
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*/
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#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8)
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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 __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
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#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
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#define __USER32_DS __USER_DS
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#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
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#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8 + 3)
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#define GDT_ENTRIES 16
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/* TLS indexes for 64-bit - 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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#endif
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#ifndef CONFIG_PARAVIRT
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#define get_kernel_rpl() 0
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# define get_kernel_rpl() 0
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#endif
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#define IDT_ENTRIES 256
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#define NUM_EXCEPTION_VECTORS 32
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/* Bitmask of exception vectors which push an error code on the stack */
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#define EXCEPTION_ERRCODE_MASK 0x00027d00
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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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#define IDT_ENTRIES 256
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#define NUM_EXCEPTION_VECTORS 32
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/* Bitmask of exception vectors which push an error code on the stack: */
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#define EXCEPTION_ERRCODE_MASK 0x00027d00
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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][2+2+5];
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#ifdef CONFIG_TRACING
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#define trace_early_idt_handlers early_idt_handlers
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# define trace_early_idt_handlers early_idt_handlers
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#endif
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/*
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@ -211,37 +258,30 @@ do { \
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} while (0)
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/*
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* Save a segment register away
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* Save a segment register away:
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*/
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#define savesegment(seg, value) \
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asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
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/*
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* x86_32 user gs accessors.
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* x86-32 user GS accessors:
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*/
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#ifdef CONFIG_X86_32
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#ifdef CONFIG_X86_32_LAZY_GS
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#define get_user_gs(regs) (u16)({unsigned long v; savesegment(gs, v); v;})
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#define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v))
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#define task_user_gs(tsk) ((tsk)->thread.gs)
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#define lazy_save_gs(v) savesegment(gs, (v))
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#define lazy_load_gs(v) loadsegment(gs, (v))
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#else /* X86_32_LAZY_GS */
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#define get_user_gs(regs) (u16)((regs)->gs)
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#define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0)
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#define task_user_gs(tsk) (task_pt_regs(tsk)->gs)
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#define lazy_save_gs(v) do { } while (0)
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#define lazy_load_gs(v) do { } while (0)
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#endif /* X86_32_LAZY_GS */
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# ifdef CONFIG_X86_32_LAZY_GS
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# define get_user_gs(regs) (u16)({ unsigned long v; savesegment(gs, v); v; })
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# define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v))
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# define task_user_gs(tsk) ((tsk)->thread.gs)
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# define lazy_save_gs(v) savesegment(gs, (v))
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# define lazy_load_gs(v) loadsegment(gs, (v))
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# else /* X86_32_LAZY_GS */
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# define get_user_gs(regs) (u16)((regs)->gs)
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# define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0)
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# define task_user_gs(tsk) (task_pt_regs(tsk)->gs)
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# define lazy_save_gs(v) do { } while (0)
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# define lazy_load_gs(v) do { } while (0)
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# endif /* X86_32_LAZY_GS */
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#endif /* X86_32 */
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static inline unsigned long get_limit(unsigned long segment)
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{
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unsigned long __limit;
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asm("lsll %1,%0" : "=r" (__limit) : "r" (segment));
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return __limit + 1;
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}
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#endif /* !__ASSEMBLY__ */
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#endif /* __KERNEL__ */
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