summaryrefslogtreecommitdiffstats
path: root/arch/x86/include/asm/segment.h
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/include/asm/segment.h')
-rw-r--r--arch/x86/include/asm/segment.h356
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 */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-27 12:21:40 +0000