xref: /openbmc/u-boot/lib/efi/efi_stub.c (revision 0963060c)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright (c) 2015 Google, Inc
4  *
5  * EFI information obtained here:
6  * http://wiki.phoenix.com/wiki/index.php/EFI_BOOT_SERVICES
7  *
8  * Loads a payload (U-Boot) within the EFI environment. This is built as an
9  * EFI application. It can be built either in 32-bit or 64-bit mode.
10  */
11 
12 #include <common.h>
13 #include <debug_uart.h>
14 #include <efi.h>
15 #include <efi_api.h>
16 #include <errno.h>
17 #include <ns16550.h>
18 #include <asm/cpu.h>
19 #include <asm/io.h>
20 #include <linux/err.h>
21 #include <linux/types.h>
22 
23 #ifndef CONFIG_X86
24 /*
25  * Problem areas:
26  * - putc() uses the ns16550 address directly and assumed I/O access. Many
27  *	platforms will use memory access
28  * get_codeseg32() is only meaningful on x86
29  */
30 #error "This file needs to be ported for use on architectures"
31 #endif
32 
33 static struct efi_priv *global_priv;
34 static bool use_uart;
35 
36 struct __packed desctab_info {
37 	uint16_t limit;
38 	uint64_t addr;
39 	uint16_t pad;
40 };
41 
42 /*
43  * EFI uses Unicode and we don't. The easiest way to get a sensible output
44  * function is to use the U-Boot debug UART. We use EFI's console output
45  * function where available, and assume the built-in UART after that. We rely
46  * on EFI to set up the UART for us and just bring in the functions here.
47  * This last bit is a bit icky, but it's only for debugging anyway. We could
48  * build in ns16550.c with some effort, but this is a payload loader after
49  * all.
50  *
51  * Note: We avoid using printf() so we don't need to bring in lib/vsprintf.c.
52  * That would require some refactoring since we already build this for U-Boot.
53  * Building an EFI shared library version would have to be a separate stem.
54  * That might push us to using the SPL framework to build this stub. However
55  * that would involve a round of EFI-specific changes in SPL. Worth
56  * considering if we start needing more U-Boot functionality. Note that we
57  * could then move get_codeseg32() to arch/x86/cpu/cpu.c.
58  */
59 void _debug_uart_init(void)
60 {
61 }
62 
63 void putc(const char ch)
64 {
65 	if (ch == '\n')
66 		putc('\r');
67 
68 	if (use_uart) {
69 		NS16550_t com_port = (NS16550_t)0x3f8;
70 
71 		while ((inb((ulong)&com_port->lsr) & UART_LSR_THRE) == 0)
72 			;
73 		outb(ch, (ulong)&com_port->thr);
74 	} else {
75 		efi_putc(global_priv, ch);
76 	}
77 }
78 
79 void puts(const char *str)
80 {
81 	while (*str)
82 		putc(*str++);
83 }
84 
85 static void _debug_uart_putc(int ch)
86 {
87 	putc(ch);
88 }
89 
90 DEBUG_UART_FUNCS
91 
92 void *memcpy(void *dest, const void *src, size_t size)
93 {
94 	unsigned char *dptr = dest;
95 	const unsigned char *ptr = src;
96 	const unsigned char *end = src + size;
97 
98 	while (ptr < end)
99 		*dptr++ = *ptr++;
100 
101 	return dest;
102 }
103 
104 void *memset(void *inptr, int ch, size_t size)
105 {
106 	char *ptr = inptr;
107 	char *end = ptr + size;
108 
109 	while (ptr < end)
110 		*ptr++ = ch;
111 
112 	return ptr;
113 }
114 
115 static void jump_to_uboot(ulong cs32, ulong addr, ulong info)
116 {
117 #ifdef CONFIG_EFI_STUB_32BIT
118 	/*
119 	 * U-Boot requires these parameters in registers, not on the stack.
120 	 * See _x86boot_start() for this code.
121 	 */
122 	typedef void (*func_t)(int bist, int unused, ulong info)
123 		__attribute__((regparm(3)));
124 
125 	((func_t)addr)(0, 0, info);
126 #else
127 	cpu_call32(cs32, CONFIG_SYS_TEXT_BASE, info);
128 #endif
129 }
130 
131 #ifdef CONFIG_EFI_STUB_64BIT
132 static void get_gdt(struct desctab_info *info)
133 {
134 	asm volatile ("sgdt %0" : : "m"(*info) : "memory");
135 }
136 #endif
137 
138 static inline unsigned long read_cr3(void)
139 {
140 	unsigned long val;
141 
142 	asm volatile("mov %%cr3,%0" : "=r" (val) : : "memory");
143 	return val;
144 }
145 
146 /**
147  * get_codeseg32() - Find the code segment to use for 32-bit code
148  *
149  * U-Boot only works in 32-bit mode at present, so when booting from 64-bit
150  * EFI we must first change to 32-bit mode. To do this we need to find the
151  * correct code segment to use (an entry in the Global Descriptor Table).
152  *
153  * @return code segment GDT offset, or 0 for 32-bit EFI, -ENOENT if not found
154  */
155 static int get_codeseg32(void)
156 {
157 	int cs32 = 0;
158 
159 #ifdef CONFIG_EFI_STUB_64BIT
160 	struct desctab_info gdt;
161 	uint64_t *ptr;
162 	int i;
163 
164 	get_gdt(&gdt);
165 	for (ptr = (uint64_t *)(unsigned long)gdt.addr, i = 0; i < gdt.limit;
166 	     i += 8, ptr++) {
167 		uint64_t desc = *ptr;
168 		uint64_t base, limit;
169 
170 		/*
171 		 * Check that the target U-Boot jump address is within the
172 		 * selector and that the selector is of the right type.
173 		 */
174 		base = ((desc >> GDT_BASE_LOW_SHIFT) & GDT_BASE_LOW_MASK) |
175 			((desc >> GDT_BASE_HIGH_SHIFT) & GDT_BASE_HIGH_MASK)
176 				<< 16;
177 		limit = ((desc >> GDT_LIMIT_LOW_SHIFT) & GDT_LIMIT_LOW_MASK) |
178 			((desc >> GDT_LIMIT_HIGH_SHIFT) & GDT_LIMIT_HIGH_MASK)
179 				<< 16;
180 		base <<= 12;	/* 4KB granularity */
181 		limit <<= 12;
182 		if ((desc & GDT_PRESENT) && (desc & GDT_NOTSYS) &&
183 		    !(desc & GDT_LONG) && (desc & GDT_4KB) &&
184 		    (desc & GDT_32BIT) && (desc & GDT_CODE) &&
185 		    CONFIG_SYS_TEXT_BASE > base &&
186 		    CONFIG_SYS_TEXT_BASE + CONFIG_SYS_MONITOR_LEN < limit
187 		) {
188 			cs32 = i;
189 			break;
190 		}
191 	}
192 
193 #ifdef DEBUG
194 	puts("\ngdt: ");
195 	printhex8(gdt.limit);
196 	puts(", addr: ");
197 	printhex8(gdt.addr >> 32);
198 	printhex8(gdt.addr);
199 	for (i = 0; i < gdt.limit; i += 8) {
200 		uint32_t *ptr = (uint32_t *)((unsigned long)gdt.addr + i);
201 
202 		puts("\n");
203 		printhex2(i);
204 		puts(": ");
205 		printhex8(ptr[1]);
206 		puts("  ");
207 		printhex8(ptr[0]);
208 	}
209 	puts("\n ");
210 	puts("32-bit code segment: ");
211 	printhex2(cs32);
212 	puts("\n ");
213 
214 	puts("page_table: ");
215 	printhex8(read_cr3());
216 	puts("\n ");
217 #endif
218 	if (!cs32) {
219 		puts("Can't find 32-bit code segment\n");
220 		return -ENOENT;
221 	}
222 #endif
223 
224 	return cs32;
225 }
226 
227 static int setup_info_table(struct efi_priv *priv, int size)
228 {
229 	struct efi_info_hdr *info;
230 	efi_status_t ret;
231 
232 	/* Get some memory for our info table */
233 	priv->info_size = size;
234 	info = efi_malloc(priv, priv->info_size, &ret);
235 	if (ret) {
236 		printhex2(ret);
237 		puts(" No memory for info table: ");
238 		return ret;
239 	}
240 
241 	memset(info, '\0', sizeof(*info));
242 	info->version = EFI_TABLE_VERSION;
243 	info->hdr_size = sizeof(*info);
244 	priv->info = info;
245 	priv->next_hdr = (char *)info + info->hdr_size;
246 
247 	return 0;
248 }
249 
250 static void add_entry_addr(struct efi_priv *priv, enum efi_entry_t type,
251 			   void *ptr1, int size1, void *ptr2, int size2)
252 {
253 	struct efi_entry_hdr *hdr = priv->next_hdr;
254 
255 	hdr->type = type;
256 	hdr->size = size1 + size2;
257 	hdr->addr = 0;
258 	hdr->link = ALIGN(sizeof(*hdr) + hdr->size, 16);
259 	priv->next_hdr += hdr->link;
260 	memcpy(hdr + 1, ptr1, size1);
261 	memcpy((void *)(hdr + 1) + size1, ptr2, size2);
262 	priv->info->total_size = (ulong)priv->next_hdr - (ulong)priv->info;
263 }
264 
265 /**
266  * efi_main() - Start an EFI image
267  *
268  * This function is called by our EFI start-up code. It handles running
269  * U-Boot. If it returns, EFI will continue.
270  */
271 efi_status_t EFIAPI efi_main(efi_handle_t image,
272 			     struct efi_system_table *sys_table)
273 {
274 	struct efi_priv local_priv, *priv = &local_priv;
275 	struct efi_boot_services *boot = sys_table->boottime;
276 	struct efi_mem_desc *desc;
277 	struct efi_entry_memmap map;
278 	struct efi_gop *gop;
279 	struct efi_entry_gopmode mode;
280 	struct efi_entry_systable table;
281 	efi_guid_t efi_gop_guid = EFI_GOP_GUID;
282 	efi_uintn_t key, desc_size, size;
283 	efi_status_t ret;
284 	u32 version;
285 	int cs32;
286 
287 	ret = efi_init(priv, "Payload", image, sys_table);
288 	if (ret) {
289 		printhex2(ret);
290 		puts(" efi_init() failed\n");
291 		return ret;
292 	}
293 	global_priv = priv;
294 
295 	cs32 = get_codeseg32();
296 	if (cs32 < 0)
297 		return EFI_UNSUPPORTED;
298 
299 	/* Get the memory map so we can switch off EFI */
300 	size = 0;
301 	ret = boot->get_memory_map(&size, NULL, &key, &desc_size, &version);
302 	if (ret != EFI_BUFFER_TOO_SMALL) {
303 		printhex2(EFI_BITS_PER_LONG);
304 		putc(' ');
305 		printhex2(ret);
306 		puts(" No memory map\n");
307 		return ret;
308 	}
309 	size += 1024;	/* Since doing a malloc() may change the memory map! */
310 	desc = efi_malloc(priv, size, &ret);
311 	if (!desc) {
312 		printhex2(ret);
313 		puts(" No memory for memory descriptor\n");
314 		return ret;
315 	}
316 	ret = setup_info_table(priv, size + 128);
317 	if (ret)
318 		return ret;
319 
320 	ret = boot->locate_protocol(&efi_gop_guid, NULL, (void **)&gop);
321 	if (ret) {
322 		puts(" GOP unavailable\n");
323 	} else {
324 		mode.fb_base = gop->mode->fb_base;
325 		mode.fb_size = gop->mode->fb_size;
326 		mode.info_size = gop->mode->info_size;
327 		add_entry_addr(priv, EFIET_GOP_MODE, &mode, sizeof(mode),
328 			       gop->mode->info,
329 			       sizeof(struct efi_gop_mode_info));
330 	}
331 
332 	ret = boot->get_memory_map(&size, desc, &key, &desc_size, &version);
333 	if (ret) {
334 		printhex2(ret);
335 		puts(" Can't get memory map\n");
336 		return ret;
337 	}
338 
339 	table.sys_table = (ulong)sys_table;
340 	add_entry_addr(priv, EFIET_SYS_TABLE, &table, sizeof(table), NULL, 0);
341 
342 	ret = boot->exit_boot_services(image, key);
343 	if (ret) {
344 		/*
345 		 * Unfortunately it happens that we cannot exit boot services
346 		 * the first time. But the second time it work. I don't know
347 		 * why but this seems to be a repeatable problem. To get
348 		 * around it, just try again.
349 		 */
350 		printhex2(ret);
351 		puts(" Can't exit boot services\n");
352 		size = sizeof(desc);
353 		ret = boot->get_memory_map(&size, desc, &key, &desc_size,
354 					   &version);
355 		if (ret) {
356 			printhex2(ret);
357 			puts(" Can't get memory map\n");
358 			return ret;
359 		}
360 		ret = boot->exit_boot_services(image, key);
361 		if (ret) {
362 			printhex2(ret);
363 			puts(" Can't exit boot services 2\n");
364 			return ret;
365 		}
366 	}
367 
368 	/* The EFI UART won't work now, switch to a debug one */
369 	use_uart = true;
370 
371 	map.version = version;
372 	map.desc_size = desc_size;
373 	add_entry_addr(priv, EFIET_MEMORY_MAP, &map, sizeof(map), desc, size);
374 	add_entry_addr(priv, EFIET_END, NULL, 0, 0, 0);
375 
376 	memcpy((void *)CONFIG_SYS_TEXT_BASE, _binary_u_boot_bin_start,
377 	       (ulong)_binary_u_boot_bin_end -
378 	       (ulong)_binary_u_boot_bin_start);
379 
380 #ifdef DEBUG
381 	puts("EFI table at ");
382 	printhex8((ulong)priv->info);
383 	puts(" size ");
384 	printhex8(priv->info->total_size);
385 #endif
386 	putc('\n');
387 	jump_to_uboot(cs32, CONFIG_SYS_TEXT_BASE, (ulong)priv->info);
388 
389 	return EFI_LOAD_ERROR;
390 }
391