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Diffstat (limited to '')
| -rw-r--r-- | arch/x86/include/asm/segment.h | 356 |
1 files changed, 356 insertions, 0 deletions
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h new file mode 100644 index 000000000..2e7890dd5 --- /dev/null +++ b/arch/x86/include/asm/segment.h @@ -0,0 +1,356 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_SEGMENT_H +#define _ASM_X86_SEGMENT_H + +#include <linux/const.h> +#include <asm/alternative.h> +#include <asm/ibt.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 + +/* + * 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 - unused + * 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_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 + +#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_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 __CPUNODE_SEG (GDT_ENTRY_CPUNODE*8 + 3) + +#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 0x20027d00 + +#define GDT_SIZE (GDT_ENTRIES*8) +#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 + ENDBR_INSN_SIZE) + +/* + * 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 + ENDBR_INSN_SIZE) + +#ifndef __ASSEMBLY__ + +extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE]; +extern void early_ignore_irq(void); + +#ifdef 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" \ + _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k0)\ + : "+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_TYPE(1b, 2b, EX_TYPE_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") + +#endif /* !__ASSEMBLY__ */ +#endif /* __KERNEL__ */ + +#endif /* _ASM_X86_SEGMENT_H */ |