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/* 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_CS8) #define __BOOT_DS (GDT_ENTRY_BOOT_DS8) #define __BOOT_TSS (GDT_ENTRY_BOOT_TSS8) /* * Bottom two bits of selector give the ring * privilege level / #define SEGMENT_RPL_MASK 0x3 / * When running on Xen PV, the actual privilege level of the kernel is 1, * not 0. Testing the Requested Privilege Level in a segment selector to * determine whether the context is user mode or kernel mode with * SEGMENT_RPL_MASK is wrong because the PV kernel's privilege level * matches the 0x3 mask. * * Testing with USER_SEGMENT_RPL_MASK is valid for both native and Xen PV * kernels because privilege level 2 is never used. / #define USER_SEGMENT_RPL_MASK 0x2 / 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_CS8) #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS8) #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS8 + 3) #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS8 + 3) #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS8) /* segment for calling fn: / #define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS328) /* code segment for BIOS: / #define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS168) /* "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_DS8) /* transfer data segment: / #define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS18) /* another data segment: / #define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS28) #ifdef CONFIG_SMP # define __KERNEL_PERCPU (GDT_ENTRY_PERCPU8) #else # define __KERNEL_PERCPU 0 #endif #ifdef CONFIG_STACKPROTECTOR # define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY8) #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 #define GDT_ENTRY_CPUNODE 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_CS8) #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS8) #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS8) #define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS8 + 3) #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS8 + 3) #define __USER32_DS __USER_DS #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS8 + 3) #define __CPUNODE_SEG (GDT_ENTRY_CPUNODE8 + 3) #endif #ifndef CONFIG_PARAVIRT_XXL # 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_ENTRIES8) #define GDT_ENTRY_TLS_ENTRIES 3 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8) #ifdef CONFIG_X86_64 /* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) / #define VDSO_CPUNODE_BITS 12 #define VDSO_CPUNODE_MASK 0xfff #ifndef __ASSEMBLY__ / Helper functions to store/load CPU and node numbers / static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node) { return (node << VDSO_CPUNODE_BITS) \| cpu; } static inline void vdso_read_cpunode(unsigned cpu, unsigned node) { unsigned int p; / * Load CPU and node number from the GDT. LSL is faster than RDTSCP * and works on all CPUs. This is volatile so that it orders * correctly with respect to barrier() and to keep GCC from cleverly * hoisting it out of the calling function. * * If RDPID is available, use it. / alternative_io ("lsl %[seg],%[p]", ".byte 0xf3,0x0f,0xc7,0xf8", / RDPID %eax/rax / X86_FEATURE_RDPID, [p] "=a" (p), [seg] "r" (__CPUNODE_SEG)); if (cpu) cpu = (p & VDSO_CPUNODE_MASK); if (node) node = (p >> VDSO_CPUNODE_BITS); } #endif / !__ASSEMBLY__ / #endif / CONFIG_X86_64 / #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 / * xen_early_idt_handler_array is for Xen pv guests: for each entry in * early_idt_handler_array it contains a prequel in the form of * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to * max 8 bytes. / #define XEN_EARLY_IDT_HANDLER_SIZE 8 #ifndef __ASSEMBLY__ extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE]; extern void early_ignore_irq(void); #if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV) extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE]; #endif / * 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"); } / __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 */

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