24 /* Size of kernel static code and data, in 4 kB pages. */
27 /* Amount of physical memory, in 4 kB pages. */
30 static void gdt_init (void);
31 void power_off (void);
34 main_thread (void *aux UNUSED)
41 char buf[DISK_SECTOR_SIZE];
42 disk_read (hda, 0, buf);
43 hex_dump (buf, sizeof buf);
47 thread_execute ("a.out");
53 extern char _text, _end, __bss_start;
56 /* Clear out the BSS segment. */
57 memset (&__bss_start, 0, &_end - &__bss_start);
59 /* Initialize components needed by printk() very early. */
62 printk ("Booting cnachos86...\n");
64 /* Calculate how much RAM the kernel uses, and find out from
65 the bootloader how much RAM this machine has. */
66 kernel_pages = (&_end - &_text + 4095) / 4096;
67 ram_pages = *(uint32_t *) (0x7e00 - 6);
68 printk ("ram: detected %'d kB.\n", ram_pages * 4);
70 /* Memory from the end of the kernel through the end of memory
71 is free. Give it to the page allocator. */
72 palloc_init ((void *) (KERN_BASE + kernel_pages * PGSIZE),
73 (void *) (PHYS_BASE + ram_pages * PGSIZE));
90 t = thread_create ("main", main_thread, NULL);
98 make_seg_desc (uint32_t base,
100 enum seg_system system,
103 enum seg_granularity granularity)
105 uint32_t e0 = ((limit & 0xffff) /* Limit 15:0. */
106 | (base << 16)); /* Base 15:0. */
107 uint32_t e1 = (((base >> 16) & 0xff) /* Base 23:16. */
108 | (system << 12) /* 0=system, 1=code/data. */
109 | (type << 8) /* Segment type. */
110 | (dpl << 13) /* Descriptor privilege. */
111 | (1 << 15) /* Present. */
112 | (limit & 0xf0000) /* Limit 16:19. */
113 | (1 << 22) /* 32-bit segment. */
114 | (granularity << 23) /* Byte/page granularity. */
115 | (base & 0xff000000)); /* Base 31:24. */
116 return e0 | ((uint64_t) e1 << 32);
120 make_code_desc (int dpl)
122 return make_seg_desc (0, 0xfffff, SYS_CODE_DATA, TYPE_CODE | TYPE_READABLE,
127 make_data_desc (int dpl)
129 return make_seg_desc (0, 0xfffff, SYS_CODE_DATA, TYPE_WRITABLE,
134 make_tss_desc (void *vaddr)
136 return make_seg_desc ((uint32_t) vaddr,
137 0x67, SYS_SYSTEM, TYPE_TSS_32_A, 0, GRAN_BYTE);
140 uint64_t gdt[SEL_CNT];
144 /* Sets up a proper GDT. The bootstrap loader's GDT didn't
145 include user-mode selectors or a TSS. */
149 uint64_t gdtr_operand;
151 /* Our TSS is never used in a call gate or task gate, so only a
152 few fields of it are ever referenced, and those are the only
153 ones we initialize. */
154 tss = palloc_get (PAL_ASSERT | PAL_ZERO);
155 tss->esp0 = (uint32_t) ptov(0x20000);
156 tss->ss0 = SEL_KDSEG;
157 tss->bitmap = 0xdfff;
159 /* Initialize GDT. */
160 gdt[SEL_NULL / sizeof *gdt] = 0;
161 gdt[SEL_KCSEG / sizeof *gdt] = make_code_desc (0);
162 gdt[SEL_KDSEG / sizeof *gdt] = make_data_desc (0);
163 gdt[SEL_UCSEG / sizeof *gdt] = make_code_desc (3);
164 gdt[SEL_UDSEG / sizeof *gdt] = make_data_desc (3);
165 gdt[SEL_TSS / sizeof *gdt] = make_tss_desc (tss);
168 gdtr_operand = make_dtr_operand (sizeof gdt - 1, gdt);
169 asm volatile ("lgdt %0" :: "m" (gdtr_operand));
170 asm volatile ("ltr %w0" :: "r" (SEL_TSS));
176 const char s[] = "Shutdown";
179 printk ("Powering off...\n");
180 for (p = s; *p != '\0'; p++)