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source: rtems/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.c @ 038e1dba

4.115

Last change on this file since 038e1dba was 038e1dba, checked in by Jan Dolezal <dolezj21@…>, on 12/03/14 at 23:56:39
i386: doxygen and comments related to VESA real mode framebuffer
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1	/**
2	* @file realmode_int.c
3	*
4	* @ingroup i386_shared
5	*
6	* @brief Real mode interrupt call implementation
7	*/
8
9	/*
10	* Copyright (c) 2014 - CTU in Prague
11	* Jan DoleÅŸal ( dolezj21@fel.cvut.cz )
12	*
13	* The license and distribution terms for this file may be
14	* found in the file LICENSE in this distribution or at
15	* http://www.rtems.org/license/LICENSE.
16	*/
17
18	#include <bsp/realmode_int.h>
19	#include <string.h>
20	#include <rtems/score/cpu.h>
21
22	/*
23	* offsets to \a i386_realmode_interrupt_registers declared in realmode_int.h
24	* used in inline assmbler for better readability
25	*/
26	#define IR_EAX_OFF "0x00"
27	#define IR_EBX_OFF "0x04"
28	#define IR_ECX_OFF "0x08"
29	#define IR_EDX_OFF "0x0C"
30	#define IR_ESI_OFF "0x10"
31	#define IR_EDI_OFF "0x14"
32	#define IR_DS_OFF "0x18"
33	#define IR_ES_OFF "0x1A"
34	#define IR_FS_OFF "0x1C"
35	#define IR_GS_OFF "0x1E"
36
37	/*
38	* offsets to \a rm_int_regs_bkp_param
39	*/
40	#define BKP_ESP_OFF "0x20"
41	#define BKP_SS_OFF "0x24"
42	#define BKP_DS_OFF "0x26"
43	#define RM_ENTRY "0x28"
44	#define PM_ENTRY "0x2C"
45
46	/**
47	* @brief parameters, results, backup values accessible in real mode
48	*
49	* @note Struct members not necessarily used in C. This serves also as
50	* layout of memory and it is used within inline assembler.
51	*/
52	typedef struct {
53	i386_realmode_interrupt_registers inoutregs;
54	/** spot for back up of protected mode stack pointer */
55	uint32_t pm_esp_bkp;
56	/** spot for back up of protected mode stack selector */
57	uint16_t pm_ss_bkp;
58	/** spot for back up of protected mode data selector */
59	uint16_t ds_bkp;
60	/** spot for setting up long indirect jump offset
61	to real mode from 16bit protected mode */
62	uint16_t rm_entry;
63	/** spot for setting up long indirect jump segment
64	to real mode from 16bit protected mode */
65	uint16_t rm_code_segment;
66	/** returning offset for long indirect jump back
67	to 32bit protected mode */
68	uint32_t pm_entry;
69	/** returning selector for long indirect jump back
70	to 32bit protected mode */
71	uint16_t pm_code_selector;
72	/* if this struct is to be modified update offset definitions as well */
73	} RTEMS_COMPILER_PACKED_ATTRIBUTE rm_int_regs_bkp_param;
74
75	/* offsets to \a pm_bkp_and_param */
76	#define BKP_IDTR_LIM "0x00"
77	#define BKP_IDTR_BASE "0x02"
78	#define BKP_ES_OFF "0x06"
79	#define BKP_FS_OFF "0x08"
80	#define BKP_GS_OFF "0x0A"
81	#define RML_ENTRY "0x0C"
82	#define RML_D_SEL "0x12"
83	#define RM_SS "0x14"
84	#define RM_SP "0x16"
85	#define RM_DS "0x18"
86
87	/**
88	* @brief backup values, pointers/parameters accessible in protected mode
89	*
90	* @note Struct members not necessarily used in C. This serves also as
91	* layout of memory and it is used within inline assembler.
92	*/
93	typedef struct {
94	/** spot for backup protected mode interrupt descriptor table register */
95	uint16_t idtr_lim_bkp;
96	/** @see idtr_lim_bkp */
97	uint32_t idtr_base_bkp;
98	/** spot to backup of ES register value in 32bit protected mode */
99	uint16_t es_bkp;
100	/** spot to backup of FS register value in 32bit protected mode */
101	uint16_t fs_bkp;
102	/** spot to backup of GS register value in 32bit protected mode */
103	uint16_t gs_bkp;
104	/** values for indirect jump to 16bit protected mode */
105	uint32_t rml_entry;
106	/** @see rml_entry */
107	uint16_t rml_code_selector;
108	/** data selector for 16bit protected mode */
109	uint16_t rml_data_selector;
110	/** values determinig location of real mode stack */
111	uint16_t rm_stack_segment;
112	/** @see rm_stack_segment */
113	uint16_t rm_stack_pointer;
114	/** data segment for real mode */
115	uint16_t rm_data_segment;
116	} RTEMS_COMPILER_PACKED_ATTRIBUTE pm_bkp_and_param;
117
118	/* addresses where we are going to put Interrupt buffer,
119	* parameter/returned/preserved values, stack and copy code
120	* for calling BIOS interrupt real mode interface
121	* The value is chosen arbitrarily in the first 640kB
122	* to be accessible for real mode. It should be out of range
123	* used by RTEMS because its base address is above 1MB.
124	* It has to be above first 4kB (or better 64kB) which could
125	* be used by BIOS.
126	*/
127	#define REAL_MODE_SPOT 0x12000
128	/* REAL_MODE_SPOT value is also top of real mode stack */
129
130	/* buffers positions and lengths */
131	#define DEFAULT_BUFFER_SIZE 512
132	static void default_rm_buffer_spot = (void )REAL_MODE_SPOT;
133	static uint16_t default_rm_buffer_size = DEFAULT_BUFFER_SIZE;
134
135	/* real mode stack */
136	#define STACK_SIZE 8192
137	#define INT_STACK_TOP REAL_MODE_SPOT
138
139	/******************************
140	* STACK * *
141	****************************** REAL_MODE_SPOT
142	* INT_BUF * 512 B *
143	******************************
144	* INT_REGs * 50 B *
145	******************************
146	* INT_FNC ~149 B
147	******************************/
148
149	#define __DP_TYPE uint8_t
150	#define __DP_YES ((__DP_TYPE)1)
151	#define __DP_NO ((__DP_TYPE)-1)
152	#define __DP_FAIL ((__DP_TYPE)0)
153	static __DP_TYPE descsPrepared = __DP_NO;
154
155	/* rml - real mode alike */
156	#define rml_limit 0xFFFF
157	static uint16_t rml_code_dsc_index = 0;
158	static uint16_t rml_data_dsc_index = 0;
159
160	/**
161	* @brief Prepares real-mode like descriptors to be used for switching
162	* to real mode.
163	*
164	* Descriptors will be placed to the GDT.
165	*
166	* @param[in] base32 32-bit physical address to be used as base for 16-bit
167	* protected mode descriptors
168	* @retval __DP_YES descriptors are prepared
169	* @retval __DP_FAIL descriptors allocation failed (GDT too small)
170	*/
171	static __DP_TYPE prepareRMDescriptors (void *base32) {
172	static void prevBase = (void )-1;
173	/* check if descriptors were prepared already */
174	if (descsPrepared == __DP_YES && prevBase == base32)
175	return descsPrepared;
176
177	if (descsPrepared == __DP_FAIL)
178	return descsPrepared;
179
180	/* create 'real mode like' segment descriptors, for switching to real mode */
181	rml_code_dsc_index = i386_next_empty_gdt_entry();
182	if (rml_code_dsc_index == 0)
183	{
184	/* not enough space in GDT */
185	descsPrepared = __DP_FAIL;
186	return descsPrepared;
187	}
188
189	segment_descriptors flags_desc;
190	memset(&flags_desc, 0, sizeof(flags_desc));
191	flags_desc.type = 0xE; /* bits 4 */
192	flags_desc.descriptor_type = 0x1; /* bits 1 */
193	flags_desc.privilege = 0x0; /* bits 2 */
194	flags_desc.present = 0x1; /* bits 1 */
195	flags_desc.available = 0x0; /* bits 1 */
196	flags_desc.fixed_value_bits = 0x0; /* bits 1 */
197	flags_desc.operation_size = 0x0; /* bits 1 */
198	flags_desc.granularity = 0x0; /* bits 1 */
199	i386_fill_segment_desc_base((unsigned)base32, &flags_desc);
200	i386_fill_segment_desc_limit(rml_limit, &flags_desc);
201	if (i386_raw_gdt_entry(rml_code_dsc_index, &flags_desc) == 0)
202	{
203	/* selector to GDT out of range */
204	descsPrepared = __DP_FAIL;
205	return descsPrepared;
206	}
207
208	rml_data_dsc_index = i386_next_empty_gdt_entry();
209	if (rml_data_dsc_index == 0)
210	{
211	/* not enough space in GDT for both descriptors */
212	descsPrepared = __DP_FAIL;
213	return descsPrepared;
214	}
215
216	flags_desc.type = 0x2; /* bits 4 */
217	if (i386_raw_gdt_entry(rml_data_dsc_index, &flags_desc) == 0)
218	{
219	/* selector to GDT out of range */
220	descsPrepared = __DP_FAIL;
221	return descsPrepared;
222	}
223	prevBase = base32;
224	descsPrepared = __DP_YES;
225	return descsPrepared;
226	}
227
228	void i386_get_default_rm_buffer(uint16_t size) {
229	*size = default_rm_buffer_size;
230	return default_rm_buffer_spot;
231	}
232
233	int i386_real_interrupt_call(uint8_t interrupt_number,
234	i386_realmode_interrupt_registers *ir)
235	{
236	uint32_t pagingon;
237	rm_int_regs_bkp_param *int_passed_regs_spot;
238	/* place where the code switching to realmode and executing
239	interrupt is coppied */
240	void *rm_swtch_code_dst;
241	void *rm_stack_top;
242
243	size_t cpLength;
244	void *cpBeg;
245
246	/* values that can be passed from protected mode are stored in this struct
247	and they are passed later to the inline assembler executing interrupt */
248	volatile pm_bkp_and_param pm_bkp, *pm_bkp_addr;
249	unsigned short unused_offset;
250
251	__asm__ volatile( "\t"
252	"movl %%cr0, %%eax\n\t"
253	"andl %1, %%eax\n"
254	: "=a"(pagingon)
255	: "i"(CR0_PAGING)
256	);
257	if (pagingon)
258	return 0;
259
260	/* located under 1MB for real mode to be able to get/set values */
261	int_passed_regs_spot = (rm_int_regs_bkp_param *)
262	(default_rm_buffer_spot+default_rm_buffer_size);
263	/* position for real mode code reallocation to the first 1MB of RAM */
264	rm_swtch_code_dst = (void *)((uint32_t)int_passed_regs_spot +
265	sizeof(*int_passed_regs_spot));
266	rm_stack_top = (void *)INT_STACK_TOP;
267
268	if (prepareRMDescriptors(int_passed_regs_spot) != __DP_YES)
269	return 0;
270
271	pm_bkp_addr = &pm_bkp;
272	i386_Physical_to_real(
273	rm_stack_top - STACK_SIZE,
274	(unsigned short *)&pm_bkp.rm_stack_segment,
275	(unsigned short *)&pm_bkp.rm_stack_pointer
276	);
277	pm_bkp.rm_stack_pointer += STACK_SIZE;
278	pm_bkp.rml_code_selector = (rml_code_dsc_index<<3);
279	pm_bkp.rml_entry = ((uint32_t)rm_swtch_code_dst -
280	(uint32_t)int_passed_regs_spot);
281	pm_bkp.rml_data_selector = (rml_data_dsc_index<<3);
282	i386_Physical_to_real(
283	int_passed_regs_spot,
284	(unsigned short *)&pm_bkp.rm_data_segment,
285	&unused_offset
286	);
287
288	int_passed_regs_spot->inoutregs = *ir;
289	/* offset from the beginning of coppied code */
290	uint16_t rm_entry_offset;
291	__asm__ volatile(
292	"movw $(rment-cp_beg), %0\n\t"
293	: "=r"(rm_entry_offset)
294	);
295	i386_Physical_to_real(
296	rm_swtch_code_dst+rm_entry_offset,
297	(unsigned short *)&int_passed_regs_spot->rm_code_segment,
298	(unsigned short *)&int_passed_regs_spot->rm_entry
299	);
300	__asm__ volatile(
301	"movl $(cp_end), %0\n\t"
302	"movw %%cs, %1\n\t"
303	: "=mr"(int_passed_regs_spot->pm_entry),
304	"=mr"(int_passed_regs_spot->pm_code_selector)
305	);
306	/* copy code for switch to real mode and
307	executing interrupt to first MB of RAM */
308	__asm__ volatile( "\t"
309	"mov $cp_end-cp_beg, %0\n\t"
310	"mov $cp_beg, %1\n\t"
311	: "=rm"(cpLength), "=rm"(cpBeg)
312	);
313	memcpy(rm_swtch_code_dst, cpBeg, cpLength);
314	/* write interrupt number to be executed */
315	uint16_t interrupt_number_off;
316	uint8_t *interrupt_number_ptr;
317	__asm__ volatile( "\t"
318	"movw $intnum-cp_beg, %0\n\t"
319	: "=rm"(interrupt_number_off)
320	);
321	interrupt_number_ptr = (uint8_t *)(rm_swtch_code_dst+interrupt_number_off);
322	*interrupt_number_ptr = interrupt_number;
323	/* execute code that jumps to coppied function, which switches to real mode,
324	loads registers with values passed to interrupt and executes interrupt */
325	__asm__ volatile( "\t"
326	/* backup stack */
327	"movl %[regs_spot], %%ebx\n\t"
328	"movl %%esp, "BKP_ESP_OFF"(%%ebx)\n\t"
329	"movw %%ss, "BKP_SS_OFF"(%%ebx)\n\t"
330	/* backup data selector */
331	"movw %%ds, "BKP_DS_OFF"(%%ebx)\n\t"
332	/* backup other selectors */
333	"movl %[pm_bkp], %%esi\n\t"
334	"movw %%es, "BKP_ES_OFF"(%%esi)\n\t"
335	"movw %%fs, "BKP_FS_OFF"(%%esi)\n\t"
336	"movw %%gs, "BKP_GS_OFF"(%%esi)\n\t"
337	/* hopefully loader does not damage interrupt table on the beginning of
338	memory; that means length: 0x3FF, base: 0x0 */
339	/* preserve idtr */
340	"movl %%esi, %%eax\n\t"
341	"addl $"BKP_IDTR_LIM", %%eax\n\t"
342	"cli\n\t"
343	"sidt (%%eax)\n\t"
344	"movl $rmidt, %%eax\n\t"
345	"lidt (%%eax)\n\t"
346	/* prepare 'real mode like' data selector */
347	"movw "RML_D_SEL"(%%esi), %%ax\n\t"
348	/* prepare real mode data segment value */
349	"xorl %%edx,%%edx\n\t"
350	"movw "RM_DS"(%%esi), %%dx\n\t"
351	/* prepare real mode stack values */
352	"movw "RM_SS"(%%esi), %%cx\n\t"
353	"movzwl "RM_SP"(%%esi), %%esp\n\t"
354	/* jump to copied function and */
355	/* load 'real mode like' code selector */
356	"ljmp *"RML_ENTRY"(%%esi)\n"
357	"rmidt:"/* limit and base for realmode interrupt descriptor table */
358	".word 0x3FF\n\t"
359	".long 0\n\t"
360	/* load 'real mode like' data selectors */
361	"cp_beg: .code16\n\t"
362	"movw %%ax, %%ss\n\t"
363	"movw %%ax, %%ds\n\t"
364	"movw %%ax, %%es\n\t"
365	"movw %%ax, %%fs\n\t"
366	"movw %%ax, %%gs\n\t"
367	/* disable protected mode */
368	"movl %%cr0, %%eax\n\t"
369	"and %[cr0_prot_dis], %%ax\n\t"
370	"movl %%eax, %%cr0\n\t"
371	/* base for data selector of 16-bit protected mode is
372	at beginning of passed regs */
373	/* flush prefetch queue by far jumping */
374	"ljmp *"RM_ENTRY"\n\t"
375	"rment: "
376	/* establish rm stack - esp was already set in 32-bit protected mode*/
377	"movw %%cx, %%ss\n\t"
378	/* set data segment (value prepared in 32-bit prot mode) */
379	"movw %%dx, %%ds\n\t"
380	/* count real mode pointer so we don't need to overuse address
381	prefix (by using 32bit addresses in 16bit context) */
382	"shll $4,%%edx\n\t"
383	"subl %%edx,%%ebx\n\t"
384	/* prepare values to be used after interrupt call */
385	"pushw %%bx\n\t"
386	"pushw %%ds\n\t"
387	/* fill registers with parameters */
388	"movw " IR_DS_OFF"(%%bx), %%ax\n\t"
389	"pushw %%ax\n\t"
390	"movl "IR_EAX_OFF"(%%bx), %%eax\n\t"
391	"movl "IR_ECX_OFF"(%%bx), %%ecx\n\t"
392	"movl "IR_EDX_OFF"(%%bx), %%edx\n\t"
393	"movl "IR_EDI_OFF"(%%bx), %%edi\n\t"
394	"movl "IR_ESI_OFF"(%%bx), %%esi\n\t"
395	"movw " IR_ES_OFF"(%%bx), %%es\n\t"
396	"movw " IR_FS_OFF"(%%bx), %%fs\n\t"
397	"movw " IR_GS_OFF"(%%bx), %%gs\n\t"
398	/* prepare ebx register */
399	"movl "IR_EBX_OFF"(%%bx), %%ebx\n\t"
400	/* prepare ds */
401	"popw %%ds\n\t"
402	/* interrupt instruction */
403	".byte 0xCD\n\t"
404	"intnum: .byte 0x0\n\t"
405	/* fill return structure */
406	"pushw %%ds\n\t"
407	"pushl %%ebx\n\t"
408	"movw 0x6(%%esp), %%ds\n\t"
409	"movw 0x8(%%esp),%%bx\n\t" /* regs_spot */
410	"movl %%eax,"IR_EAX_OFF"(%%bx)\n\t"
411	"popl %%eax\n\t"
412	"movl %%eax,"IR_EBX_OFF"(%%bx)\n\t"
413	"movl %%ecx,"IR_ECX_OFF"(%%bx)\n\t"
414	"movl %%edx,"IR_EDX_OFF"(%%bx)\n\t"
415	"movl %%esi,"IR_ESI_OFF"(%%bx)\n\t"
416	"movl %%edi,"IR_EDI_OFF"(%%bx)\n\t"
417	"popw %%ax\n\t"
418	"movw %%ax, " IR_DS_OFF"(%%bx)\n\t"
419	"movw %%es, " IR_ES_OFF"(%%bx)\n\t"
420	"movw %%fs, " IR_FS_OFF"(%%bx)\n\t"
421	"movw %%gs, " IR_GS_OFF"(%%bx)\n\t"
422	/* prepare protected mode data segment */
423	"movw "BKP_DS_OFF"(%%bx), %%ax\n\t"
424	/* restore protected mode stack values */
425	"movl "BKP_ESP_OFF"(%%bx),%%esp\n\t"
426	"movw "BKP_SS_OFF"(%%bx), %%dx\n\t"
427	/* return to protected mode */
428	"movl %%cr0, %%ecx \n\t"
429	"or %[cr0_prot_ena], %%cx\n\t"
430	"movl %%ecx, %%cr0 \n\t"
431	"ljmpl *"PM_ENTRY"(%%bx)\n\t"
432	".code32\n"
433	/* reload segmentation registers */
434	"cp_end:"
435	"movw %%ax, %%ds\n\t"
436	/* restore stack segment in protected mode context */
437	"movw %%dx, %%ss\n\t"
438	"movl %[pm_bkp], %%esi\n\t"
439	"movw "BKP_ES_OFF"(%%esi), %%es\n\t"
440	"movw "BKP_FS_OFF"(%%esi), %%fs\n\t"
441	"movw "BKP_GS_OFF"(%%esi), %%gs\n\t"
442	/* restore IDTR */
443	"addl $"BKP_IDTR_LIM", %%esi\n\t"
444	"lidt (%%esi)\n\t"
445	:
446	: [regs_spot]"m"(int_passed_regs_spot),
447	[pm_bkp]"m"(pm_bkp_addr),
448	[cr0_prot_ena]"i"(CR0_PROTECTION_ENABLE),
449	[cr0_prot_dis]"i"(~CR0_PROTECTION_ENABLE)
450	: "memory", "ebx", "ecx", "edx", "esi", "edi"
451	);
452	*ir = int_passed_regs_spot->inoutregs;
453	return 1;
454	}

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