Release 4.14 arch/x86/include/asm/segment.h
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_SEGMENT_H
#define _ASM_X86_SEGMENT_H
#include <linux/const.h>
#include <asm/alternative.h>
/*
* Constructor for a conventional segment GDT (or LDT) entry.
* This is a macro so it can be used in initializers.
*/
#define GDT_ENTRY(flags, base, limit) \
((((base) & _AC(0xff000000,ULL)) << (56-24)) | \
(((flags) & _AC(0x0000f0ff,ULL)) << 40) | \
(((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \
(((base) & _AC(0x00ffffff,ULL)) << 16) | \
(((limit) & _AC(0x0000ffff,ULL))))
/* Simple and small GDT entries for booting only: */
#define GDT_ENTRY_BOOT_CS 2
#define GDT_ENTRY_BOOT_DS 3
#define GDT_ENTRY_BOOT_TSS 4
#define __BOOT_CS (GDT_ENTRY_BOOT_CS*8)
#define __BOOT_DS (GDT_ENTRY_BOOT_DS*8)
#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS*8)
/*
* Bottom two bits of selector give the ring
* privilege level
*/
#define SEGMENT_RPL_MASK 0x3
/* User mode is privilege level 3: */
#define USER_RPL 0x3
/* Bit 2 is Table Indicator (TI): selects between LDT or GDT */
#define SEGMENT_TI_MASK 0x4
/* LDT segment has TI set ... */
#define SEGMENT_LDT 0x4
/* ... GDT has it cleared */
#define SEGMENT_GDT 0x0
#define GDT_ENTRY_INVALID_SEG 0
#ifdef CONFIG_X86_32
/*
* The layout of the per-CPU GDT under Linux:
*
* 0 - null <=== cacheline #1
* 1 - reserved
* 2 - reserved
* 3 - reserved
*
* 4 - unused <=== cacheline #2
* 5 - unused
*
* ------- start of TLS (Thread-Local Storage) segments:
*
* 6 - TLS segment #1 [ glibc's TLS segment ]
* 7 - TLS segment #2 [ Wine's %fs Win32 segment ]
* 8 - TLS segment #3 <=== cacheline #3
* 9 - reserved
* 10 - reserved
* 11 - reserved
*
* ------- start of kernel segments:
*
* 12 - kernel code segment <=== cacheline #4
* 13 - kernel data segment
* 14 - default user CS
* 15 - default user DS
* 16 - TSS <=== cacheline #5
* 17 - LDT
* 18 - PNPBIOS support (16->32 gate)
* 19 - PNPBIOS support
* 20 - PNPBIOS support <=== cacheline #6
* 21 - PNPBIOS support
* 22 - PNPBIOS support
* 23 - APM BIOS support
* 24 - APM BIOS support <=== cacheline #7
* 25 - APM BIOS support
*
* 26 - ESPFIX small SS
* 27 - per-cpu [ offset to per-cpu data area ]
* 28 - stack_canary-20 [ for stack protector ] <=== cacheline #8
* 29 - unused
* 30 - unused
* 31 - TSS for double fault handler
*/
#define GDT_ENTRY_TLS_MIN 6
#define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
#define GDT_ENTRY_KERNEL_CS 12
#define GDT_ENTRY_KERNEL_DS 13
#define GDT_ENTRY_DEFAULT_USER_CS 14
#define GDT_ENTRY_DEFAULT_USER_DS 15
#define GDT_ENTRY_TSS 16
#define GDT_ENTRY_LDT 17
#define GDT_ENTRY_PNPBIOS_CS32 18
#define GDT_ENTRY_PNPBIOS_CS16 19
#define GDT_ENTRY_PNPBIOS_DS 20
#define GDT_ENTRY_PNPBIOS_TS1 21
#define GDT_ENTRY_PNPBIOS_TS2 22
#define GDT_ENTRY_APMBIOS_BASE 23
#define GDT_ENTRY_ESPFIX_SS 26
#define GDT_ENTRY_PERCPU 27
#define GDT_ENTRY_STACK_CANARY 28
#define GDT_ENTRY_DOUBLEFAULT_TSS 31
/*
* Number of entries in the GDT table:
*/
#define GDT_ENTRIES 32
/*
* Segment selector values corresponding to the above entries:
*/
#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8)
#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8)
#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
#define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8)
/* segment for calling fn: */
#define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32*8)
/* code segment for BIOS: */
#define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16*8)
/* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32)
/* data segment for BIOS: */
#define PNP_DS (GDT_ENTRY_PNPBIOS_DS*8)
/* transfer data segment: */
#define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1*8)
/* another data segment: */
#define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2*8)
#ifdef CONFIG_SMP
# define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8)
#else
# define __KERNEL_PERCPU 0
#endif
#ifdef CONFIG_CC_STACKPROTECTOR
# define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8)
#else
# define __KERNEL_STACK_CANARY 0
#endif
#else /* 64-bit: */
#include <asm/cache.h>
#define GDT_ENTRY_KERNEL32_CS 1
#define GDT_ENTRY_KERNEL_CS 2
#define GDT_ENTRY_KERNEL_DS 3
/*
* We cannot use the same code segment descriptor for user and kernel mode,
* not even in long flat mode, because of different DPL.
*
* GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
* selectors:
*
* if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
* if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
*
* ss = STAR.SYSRET_CS+8 (in either case)
*
* thus USER_DS should be between 32-bit and 64-bit code selectors:
*/
#define GDT_ENTRY_DEFAULT_USER32_CS 4
#define GDT_ENTRY_DEFAULT_USER_DS 5
#define GDT_ENTRY_DEFAULT_USER_CS 6
/* Needs two entries */
#define GDT_ENTRY_TSS 8
/* Needs two entries */
#define GDT_ENTRY_LDT 10
#define GDT_ENTRY_TLS_MIN 12
#define GDT_ENTRY_TLS_MAX 14
/* Abused to load per CPU data from limit */
#define GDT_ENTRY_PER_CPU 15
/*
* Number of entries in the GDT table:
*/
#define GDT_ENTRIES 16
/*
* Segment selector values corresponding to the above entries:
*
* Note, selectors also need to have a correct RPL,
* expressed with the +3 value for user-space selectors:
*/
#define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8)
#define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8)
#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8)
#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
#define __USER32_DS __USER_DS
#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8 + 3)
#endif
#ifndef CONFIG_PARAVIRT
# define get_kernel_rpl() 0
#endif
#define IDT_ENTRIES 256
#define NUM_EXCEPTION_VECTORS 32
/* Bitmask of exception vectors which push an error code on the stack: */
#define EXCEPTION_ERRCODE_MASK 0x00027d00
#define GDT_SIZE (GDT_ENTRIES*8)
#define GDT_ENTRY_TLS_ENTRIES 3
#define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8)
#ifdef __KERNEL__
/*
* early_idt_handler_array is an array of entry points referenced in the
* early IDT. For simplicity, it's a real array with one entry point
* every nine bytes. That leaves room for an optional 'push $0' if the
* vector has no error code (two bytes), a 'push $vector_number' (two
* bytes), and a jump to the common entry code (up to five bytes).
*/
#define EARLY_IDT_HANDLER_SIZE 9
#ifndef __ASSEMBLY__
extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
extern void early_ignore_irq(void);
/*
* Load a segment. Fall back on loading the zero segment if something goes
* wrong. This variant assumes that loading zero fully clears the segment.
* This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
* failure to fully clear the cached descriptor is only observable for
* FS and GS.
*/
#define __loadsegment_simple(seg, value) \
do { \
unsigned short __val = (value); \
\
asm volatile(" \n" \
"1: movl %k0,%%" #seg " \n" \
\
".section .fixup,\"ax\" \n" \
"2: xorl %k0,%k0 \n" \
" jmp 1b \n" \
".previous \n" \
\
_ASM_EXTABLE(1b, 2b) \
\
: "+r" (__val) : : "memory"); \
} while (0)
#define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
#define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
#define __loadsegment_es(value) __loadsegment_simple(es, (value))
#ifdef CONFIG_X86_32
/*
* On 32-bit systems, the hidden parts of FS and GS are unobservable if
* the selector is NULL, so there's no funny business here.
*/
#define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
#define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
#else
static inline void __loadsegment_fs(unsigned short value)
{
asm volatile(" \n"
"1: movw %0, %%fs \n"
"2: \n"
_ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs)
: : "rm" (value) : "memory");
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Andrew Lutomirski | 14 | 100.00% | 1 | 100.00% |
| Total | 14 | 100.00% | 1 | 100.00% |
/* __loadsegment_gs is intentionally undefined. Use load_gs_index instead. */
#endif
#define loadsegment(seg, value) __loadsegment_ ## seg (value)
/*
* Save a segment register away:
*/
#define savesegment(seg, value) \
asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
/*
* x86-32 user GS accessors:
*/
#ifdef CONFIG_X86_32
# ifdef CONFIG_X86_32_LAZY_GS
# define get_user_gs(regs) (u16)({ unsigned long v; savesegment(gs, v); v; })
# define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v))
# define task_user_gs(tsk) ((tsk)->thread.gs)
# define lazy_save_gs(v) savesegment(gs, (v))
# define lazy_load_gs(v) loadsegment(gs, (v))
# else /* X86_32_LAZY_GS */
# define get_user_gs(regs) (u16)((regs)->gs)
# define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0)
# define task_user_gs(tsk) (task_pt_regs(tsk)->gs)
# define lazy_save_gs(v) do { } while (0)
# define lazy_load_gs(v) do { } while (0)
# endif /* X86_32_LAZY_GS */
#endif /* X86_32 */
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _ASM_X86_SEGMENT_H */
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Glauber de Oliveira Costa | 143 | 24.20% | 4 | 17.39% |
| David Howells | 109 | 18.44% | 1 | 4.35% |
| Denys Vlasenko | 95 | 16.07% | 1 | 4.35% |
| Andrew Lutomirski | 79 | 13.37% | 2 | 8.70% |
| Ingo Molnar | 62 | 10.49% | 1 | 4.35% |
| H. Peter Anvin | 37 | 6.26% | 6 | 26.09% |
| Borislav Petkov | 20 | 3.38% | 2 | 8.70% |
| Roland McGrath | 18 | 3.05% | 1 | 4.35% |
| Thomas Gleixner | 16 | 2.71% | 2 | 8.70% |
| Tejun Heo | 6 | 1.02% | 1 | 4.35% |
| Andi Kleen | 5 | 0.85% | 1 | 4.35% |
| Greg Kroah-Hartman | 1 | 0.17% | 1 | 4.35% |
| Total | 591 | 100.00% | 23 | 100.00% |
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