/*
 * hal_segmentation.h - Segmentation-related values and structures
 * 
 * Copyright (c) 2017 Maxime Villard
 * 
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS-MKH is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS-MKH.; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

/*
 * The GDT has NGDT_MEM entries of 8-byte-sized, static memory entries. Then
 * there is a certain number of 16-byte-sized TSS entries, one for each CPU.
 */
#define GDT_NULL_SEL	0	/* Null descriptor */
#define GDT_KCODE_SEL	1	/* Kernel code descriptor */
#define GDT_KDATA_SEL	2	/* Kernel data descriptor */
#define GDT_UCODE_SEL	3	/* User code descriptor */
#define GDT_UDATA_SEL	4	/* User data descriptor */
#define NGDT_MEM	6		/* aligned */

#define GDT_CPU0TSS_SEL	0	/* cpu0's tss */
#define NGDT_DYN	(256 - (NGDT_MEM / 2) * 16)

/*
 * GDT Selectors Privileges
 */
#define ISPL(s)		((s) & SEL_RPL)
#define USERMODE(c, f)		(ISPL(c) == SEL_UPL)
#define KERNELMODE(c, f)	(ISPL(c) == SEL_KPL)
#define SEL_KPL		0		/* kernel privilege level */
#define SEL_UPL		3		/* user privilege level */
#define SEL_RPL		3		/* requester's privilege level mask */
#define SEL_LDT		4		/* local descriptor table */

#define SYSSEL_START	(NGDT_MEM * 8)

/* Create a selector, with an index and a privilege */
#define GDT_FIXED_SEL(s,r)	(((s) << 3) | r)
#define GDT_DYNAM_SEL(s,r)	((SYSSEL_START + ((s) << 4)) | r)

#ifndef x86_ASM

/*
 * Offsets.
 */
#define GDT_ADDR_MEM(s,i)	\
	((struct gdt_memseg *)((s) + ((i) << 3)))
#define GDT_ADDR_SYS(s,i)	\
	((struct gdt_sysseg *)((s) + (SYSSEL_START + ((i) << 4))))

/*
 * System segment descriptor (16 bytes): used for TSS and LDT.
 */
struct gdt_sysseg {
	uint64_t sd_lolimit:16;	/* segment extent (lsb) */
	uint64_t sd_lobase:24;	/* segment base address (lsb) */
	uint64_t sd_type:5;	/* segment type */
	uint64_t sd_dpl:2;	/* segment descriptor priority level */
	uint64_t sd_p:1;	/* segment descriptor present */
	uint64_t sd_hilimit:4;	/* segment extent (msb) */
	uint64_t sd_xx1:3;	/* avl, long and def32 (not used) */
	uint64_t sd_gran:1;	/* limit granularity (byte/page) */
	uint64_t sd_hibase:40;	/* segment base address (msb) */
	uint64_t sd_xx2:8;	/* reserved */
	uint64_t sd_zero:5;	/* must be zero */
	uint64_t sd_xx3:19;	/* reserved */
} __packed;

/*
 * Memory segment descriptor (8 bytes): used for cs, ds, etc.
 */
struct gdt_memseg {
	unsigned sd_lolimit:16;	/* segment extent (lsb) */
	unsigned sd_lobase:24;	/* segment base address (lsb) */
	unsigned sd_type:5;	/* segment type */
	unsigned sd_dpl:2;	/* segment descriptor priority level */
	unsigned sd_p:1;	/* segment descriptor present */
	unsigned sd_hilimit:4;	/* segment extent (msb) */
	unsigned sd_avl:1;	/* available */
	unsigned sd_long:1;	/* long mode */
	unsigned sd_def32:1;	/* default 32 vs 16 bit size */
	unsigned sd_gran:1;	/* limit granularity (byte/page) */
	unsigned sd_hibase:8;	/* segment base address (msb) */
} __packed;

/*
 * Common part of the above structures. Used to walk descriptor tables.
 */
struct common_segment_descriptor {
	unsigned sdc_lolimit:16;
	unsigned sdc_lobase:24;
	unsigned sdc_type:5;
	unsigned sdc_other:19;
} __packed;

/*
 * IDT descriptors (16 bytes).
 */
struct idt_seg {
	uint64_t gd_looffset:16;/* gate offset (lsb) */
	uint64_t gd_selector:16;/* gate segment selector */
	uint64_t gd_ist:3;	/* IST select */
	uint64_t gd_xx1:5;	/* reserved */
	uint64_t gd_type:5;	/* segment type */
	uint64_t gd_dpl:2;	/* segment descriptor priority level */
	uint64_t gd_p:1;	/* segment descriptor present */
	uint64_t gd_hioffset:48;/* gate offset (msb) */
	uint64_t gd_xx2:8;	/* reserved */
	uint64_t gd_zero:5;	/* must be zero */
	uint64_t gd_xx3:19;	/* reserved */
} __packed;

/*
 * Region descriptors, used to load gdt/idt tables before segments yet exist.
 */
struct region_descriptor {
	uint16_t rd_limit;	/* segment extent */
	uint64_t rd_base;	/* base address  */
} __packed;

struct tss {
	uint32_t tss_reserved1;
	uint64_t tss_rsp0;
	uint64_t tss_rsp1;
	uint64_t tss_rsp3;
	uint32_t tss_reserved2;
	uint32_t tss_reserved3;
	uint64_t tss_ist[7];
	uint32_t tss_reserved4;
	uint32_t tss_reserved5;
	uint32_t tss_iobase;
} __packed;

#define IOMAP_INVALOFF	0xffff

void lgdt(struct region_descriptor *);
void lidt(struct region_descriptor *);
void ltr(uint16_t);

#endif /* !x86_ASM */

/* system segments and gate types */
#define SDT_SYSNULL	 0	/* system null */
#define SDT_SYS286TSS	 1	/* system 286 TSS available */
#define SDT_SYSLDT	 2	/* system local descriptor table */
#define SDT_SYS286BSY	 3	/* system 286 TSS busy */
#define SDT_SYS286CGT	 4	/* system 286 call gate */
#define SDT_SYSTASKGT	 5	/* system task gate */
#define SDT_SYS286IGT	 6	/* system 286 interrupt gate */
#define SDT_SYS286TGT	 7	/* system 286 trap gate */
#define SDT_SYSNULL2	 8	/* system null again */
#define SDT_SYS386TSS	 9	/* system 386 TSS available */
#define SDT_SYSNULL3	10	/* system null again */
#define SDT_SYS386BSY	11	/* system 386 TSS busy */
#define SDT_SYS386CGT	12	/* system 386 call gate */
#define SDT_SYSNULL4	13	/* system null again */
#define SDT_SYS386IGT	14	/* system 386 interrupt gate */
#define SDT_SYS386TGT	15	/* system 386 trap gate */

/* memory segment types */
#define SDT_MEMRO	16	/* memory read only */
#define SDT_MEMROA	17	/* memory read only accessed */
#define SDT_MEMRW	18	/* memory read write */
#define SDT_MEMRWA	19	/* memory read write accessed */
#define SDT_MEMROD	20	/* memory read only expand dwn limit */
#define SDT_MEMRODA	21	/* memory read only expand dwn limit accessed */
#define SDT_MEMRWD	22	/* memory read write expand dwn limit */
#define SDT_MEMRWDA	23	/* memory read write expand dwn limit accessed */
#define SDT_MEME	24	/* memory execute only */
#define SDT_MEMEA	25	/* memory execute only accessed */
#define SDT_MEMER	26	/* memory execute read */
#define SDT_MEMERA	27	/* memory execute read accessed */
#define SDT_MEMEC	28	/* memory execute only conforming */
#define SDT_MEMEAC	29	/* memory execute only accessed conforming */
#define SDT_MEMERC	30	/* memory execute read conforming */
#define SDT_MEMERAC	31	/* memory execute read accessed conforming */

/*
 * Entries in the Interrupt Descriptor Table (IDT)
 */
#define NCPUIDT	32	/* reserved entries for CPU exceptions */
#define NIDT	256	/* total number of IDT entries */

