/** * @file realmode_int.c * * @ingroup i386_shared * * @brief Real mode interrupt call implementation */ /* * Copyright (c) 2014 - CTU in Prague * Jan Doležal ( dolezj21@fel.cvut.cz ) * * The license and distribution terms for this file may be * found in the file LICENSE in this distribution or at * http://www.rtems.org/license/LICENSE. */ #include #include #include /* * offsets to \a i386_realmode_interrupt_registers declared in realmode_int.h * used in inline assmbler for better readability */ #define IR_EAX_OFF "0x00" #define IR_EBX_OFF "0x04" #define IR_ECX_OFF "0x08" #define IR_EDX_OFF "0x0C" #define IR_ESI_OFF "0x10" #define IR_EDI_OFF "0x14" #define IR_DS_OFF "0x18" #define IR_ES_OFF "0x1A" #define IR_FS_OFF "0x1C" #define IR_GS_OFF "0x1E" /* * offsets to \a rm_int_regs_bkp_param */ #define BKP_ESP_OFF "0x20" #define BKP_SS_OFF "0x24" #define BKP_DS_OFF "0x26" #define RM_ENTRY "0x28" #define PM_ENTRY "0x2C" /** * @brief parameters, results, backup values accessible in real mode * * @note Struct members not necessarily used in C. This serves also as * layout of memory and it is used within inline assembler. */ typedef struct { i386_realmode_interrupt_registers inoutregs; /** spot for back up of protected mode stack pointer */ uint32_t pm_esp_bkp; /** spot for back up of protected mode stack selector */ uint16_t pm_ss_bkp; /** spot for back up of protected mode data selector */ uint16_t ds_bkp; /** spot for setting up long indirect jump offset to real mode from 16bit protected mode */ uint16_t rm_entry; /** spot for setting up long indirect jump segment to real mode from 16bit protected mode */ uint16_t rm_code_segment; /** returning offset for long indirect jump back to 32bit protected mode */ uint32_t pm_entry; /** returning selector for long indirect jump back to 32bit protected mode */ uint16_t pm_code_selector; /* if this struct is to be modified update offset definitions as well */ } RTEMS_COMPILER_PACKED_ATTRIBUTE rm_int_regs_bkp_param; /* offsets to \a pm_bkp_and_param */ #define BKP_IDTR_LIM "0x00" #define BKP_IDTR_BASE "0x02" #define BKP_ES_OFF "0x06" #define BKP_FS_OFF "0x08" #define BKP_GS_OFF "0x0A" #define RML_ENTRY "0x0C" #define RML_D_SEL "0x12" #define RM_SS "0x14" #define RM_SP "0x16" #define RM_DS "0x18" /** * @brief backup values, pointers/parameters accessible in protected mode * * @note Struct members not necessarily used in C. This serves also as * layout of memory and it is used within inline assembler. */ typedef struct { /** spot for backup protected mode interrupt descriptor table register */ uint16_t idtr_lim_bkp; /** @see idtr_lim_bkp */ uint32_t idtr_base_bkp; /** spot to backup of ES register value in 32bit protected mode */ uint16_t es_bkp; /** spot to backup of FS register value in 32bit protected mode */ uint16_t fs_bkp; /** spot to backup of GS register value in 32bit protected mode */ uint16_t gs_bkp; /** values for indirect jump to 16bit protected mode */ uint32_t rml_entry; /** @see rml_entry */ uint16_t rml_code_selector; /** data selector for 16bit protected mode */ uint16_t rml_data_selector; /** values determinig location of real mode stack */ uint16_t rm_stack_segment; /** @see rm_stack_segment */ uint16_t rm_stack_pointer; /** data segment for real mode */ uint16_t rm_data_segment; } RTEMS_COMPILER_PACKED_ATTRIBUTE pm_bkp_and_param; /* addresses where we are going to put Interrupt buffer, * parameter/returned/preserved values, stack and copy code * for calling BIOS interrupt real mode interface * The value is chosen arbitrarily in the first 640kB * to be accessible for real mode. It should be out of range * used by RTEMS because its base address is above 1MB. * It has to be above first 4kB (or better 64kB) which could * be used by BIOS. */ #define REAL_MODE_SPOT 0x12000 /* REAL_MODE_SPOT value is also top of real mode stack */ /* buffers positions and lengths */ #define DEFAULT_BUFFER_SIZE 512 static void *default_rm_buffer_spot = (void *)REAL_MODE_SPOT; static uint16_t default_rm_buffer_size = DEFAULT_BUFFER_SIZE; /* real mode stack */ #define STACK_SIZE 8192 #define INT_STACK_TOP REAL_MODE_SPOT /****************************** * STACK * * ****************************** REAL_MODE_SPOT * INT_BUF * 512 B * ****************************** * INT_REGs * 50 B * ****************************** * INT_FNC *~149 B * ******************************/ #define __DP_TYPE uint8_t #define __DP_YES ((__DP_TYPE)1) #define __DP_NO ((__DP_TYPE)-1) #define __DP_FAIL ((__DP_TYPE)0) static __DP_TYPE descsPrepared = __DP_NO; /* rml - real mode alike */ #define rml_limit 0xFFFF static uint16_t rml_code_dsc_index = 0; static uint16_t rml_data_dsc_index = 0; /** * @brief Prepares real-mode like descriptors to be used for switching * to real mode. * * Descriptors will be placed to the GDT. * * @param[in] base32 32-bit physical address to be used as base for 16-bit * protected mode descriptors * @retval __DP_YES descriptors are prepared * @retval __DP_FAIL descriptors allocation failed (GDT too small) */ static __DP_TYPE prepareRMDescriptors (void *base32) { static void *prevBase = (void *)-1; /* check if descriptors were prepared already */ if (descsPrepared == __DP_YES && prevBase == base32) return descsPrepared; if (descsPrepared == __DP_FAIL) return descsPrepared; /* create 'real mode like' segment descriptors, for switching to real mode */ rml_code_dsc_index = i386_next_empty_gdt_entry(); if (rml_code_dsc_index == 0) { /* not enough space in GDT */ descsPrepared = __DP_FAIL; return descsPrepared; } segment_descriptors flags_desc; memset(&flags_desc, 0, sizeof(flags_desc)); flags_desc.type = 0xE; /* bits 4 */ flags_desc.descriptor_type = 0x1; /* bits 1 */ flags_desc.privilege = 0x0; /* bits 2 */ flags_desc.present = 0x1; /* bits 1 */ flags_desc.available = 0x0; /* bits 1 */ flags_desc.fixed_value_bits = 0x0; /* bits 1 */ flags_desc.operation_size = 0x0; /* bits 1 */ flags_desc.granularity = 0x0; /* bits 1 */ i386_fill_segment_desc_base((unsigned)base32, &flags_desc); i386_fill_segment_desc_limit(rml_limit, &flags_desc); if (i386_raw_gdt_entry(rml_code_dsc_index, &flags_desc) == 0) { /* selector to GDT out of range */ descsPrepared = __DP_FAIL; return descsPrepared; } rml_data_dsc_index = i386_next_empty_gdt_entry(); if (rml_data_dsc_index == 0) { /* not enough space in GDT for both descriptors */ descsPrepared = __DP_FAIL; return descsPrepared; } flags_desc.type = 0x2; /* bits 4 */ if (i386_raw_gdt_entry(rml_data_dsc_index, &flags_desc) == 0) { /* selector to GDT out of range */ descsPrepared = __DP_FAIL; return descsPrepared; } prevBase = base32; descsPrepared = __DP_YES; return descsPrepared; } void *i386_get_default_rm_buffer(uint16_t *size) { *size = default_rm_buffer_size; return default_rm_buffer_spot; } int i386_real_interrupt_call(uint8_t interrupt_number, i386_realmode_interrupt_registers *ir) { uint32_t pagingon; rm_int_regs_bkp_param *int_passed_regs_spot; /* place where the code switching to realmode and executing interrupt is coppied */ void *rm_swtch_code_dst; void *rm_stack_top; size_t cpLength; void *cpBeg; /* values that can be passed from protected mode are stored in this struct and they are passed later to the inline assembler executing interrupt */ volatile pm_bkp_and_param pm_bkp, *pm_bkp_addr; unsigned short unused_offset; __asm__ volatile( "\t" "movl %%cr0, %%eax\n\t" "andl %1, %%eax\n" : "=a"(pagingon) : "i"(CR0_PAGING) ); if (pagingon) return 0; /* located under 1MB for real mode to be able to get/set values */ int_passed_regs_spot = (rm_int_regs_bkp_param *) (default_rm_buffer_spot+default_rm_buffer_size); /* position for real mode code reallocation to the first 1MB of RAM */ rm_swtch_code_dst = (void *)((uint32_t)int_passed_regs_spot + sizeof(*int_passed_regs_spot)); rm_stack_top = (void *)INT_STACK_TOP; if (prepareRMDescriptors(int_passed_regs_spot) != __DP_YES) return 0; pm_bkp_addr = &pm_bkp; i386_Physical_to_real( rm_stack_top - STACK_SIZE, (unsigned short *)&pm_bkp.rm_stack_segment, (unsigned short *)&pm_bkp.rm_stack_pointer ); pm_bkp.rm_stack_pointer += STACK_SIZE; pm_bkp.rml_code_selector = (rml_code_dsc_index<<3); pm_bkp.rml_entry = ((uint32_t)rm_swtch_code_dst - (uint32_t)int_passed_regs_spot); pm_bkp.rml_data_selector = (rml_data_dsc_index<<3); i386_Physical_to_real( int_passed_regs_spot, (unsigned short *)&pm_bkp.rm_data_segment, &unused_offset ); int_passed_regs_spot->inoutregs = *ir; /* offset from the beginning of coppied code */ uint16_t rm_entry_offset; __asm__ volatile( "movw $(rment-cp_beg), %0\n\t" : "=r"(rm_entry_offset) ); i386_Physical_to_real( rm_swtch_code_dst+rm_entry_offset, (unsigned short *)&int_passed_regs_spot->rm_code_segment, (unsigned short *)&int_passed_regs_spot->rm_entry ); __asm__ volatile( "movl $(cp_end), %0\n\t" "movw %%cs, %1\n\t" : "=mr"(int_passed_regs_spot->pm_entry), "=mr"(int_passed_regs_spot->pm_code_selector) ); /* copy code for switch to real mode and executing interrupt to first MB of RAM */ __asm__ volatile( "\t" "mov $cp_end-cp_beg, %0\n\t" "mov $cp_beg, %1\n\t" : "=rm"(cpLength), "=rm"(cpBeg) ); memcpy(rm_swtch_code_dst, cpBeg, cpLength); /* write interrupt number to be executed */ uint16_t interrupt_number_off; uint8_t *interrupt_number_ptr; __asm__ volatile( "\t" "movw $intnum-cp_beg, %0\n\t" : "=rm"(interrupt_number_off) ); interrupt_number_ptr = (uint8_t *)(rm_swtch_code_dst+interrupt_number_off); *interrupt_number_ptr = interrupt_number; /* execute code that jumps to coppied function, which switches to real mode, loads registers with values passed to interrupt and executes interrupt */ __asm__ volatile( "\t" /* backup stack */ "movl %[regs_spot], %%ebx\n\t" "movl %%esp, "BKP_ESP_OFF"(%%ebx)\n\t" "movw %%ss, "BKP_SS_OFF"(%%ebx)\n\t" /* backup data selector */ "movw %%ds, "BKP_DS_OFF"(%%ebx)\n\t" /* backup other selectors */ "movl %[pm_bkp], %%esi\n\t" "movw %%es, "BKP_ES_OFF"(%%esi)\n\t" "movw %%fs, "BKP_FS_OFF"(%%esi)\n\t" "movw %%gs, "BKP_GS_OFF"(%%esi)\n\t" /* hopefully loader does not damage interrupt table on the beginning of memory; that means length: 0x3FF, base: 0x0 */ /* preserve idtr */ "movl %%esi, %%eax\n\t" "addl $"BKP_IDTR_LIM", %%eax\n\t" "cli\n\t" "sidt (%%eax)\n\t" "movl $rmidt, %%eax\n\t" "lidt (%%eax)\n\t" /* prepare 'real mode like' data selector */ "movw "RML_D_SEL"(%%esi), %%ax\n\t" /* prepare real mode data segment value */ "xorl %%edx,%%edx\n\t" "movw "RM_DS"(%%esi), %%dx\n\t" /* prepare real mode stack values */ "movw "RM_SS"(%%esi), %%cx\n\t" "movzwl "RM_SP"(%%esi), %%esp\n\t" /* jump to copied function and */ /* load 'real mode like' code selector */ "ljmp *"RML_ENTRY"(%%esi)\n" "rmidt:"/* limit and base for realmode interrupt descriptor table */ ".word 0x3FF\n\t" ".long 0\n\t" /* load 'real mode like' data selectors */ "cp_beg: .code16\n\t" "movw %%ax, %%ss\n\t" "movw %%ax, %%ds\n\t" "movw %%ax, %%es\n\t" "movw %%ax, %%fs\n\t" "movw %%ax, %%gs\n\t" /* disable protected mode */ "movl %%cr0, %%eax\n\t" "and %[cr0_prot_dis], %%ax\n\t" "movl %%eax, %%cr0\n\t" /* base for data selector of 16-bit protected mode is at beginning of passed regs */ /* flush prefetch queue by far jumping */ "ljmp *"RM_ENTRY"\n\t" "rment: " /* establish rm stack - esp was already set in 32-bit protected mode*/ "movw %%cx, %%ss\n\t" /* set data segment (value prepared in 32-bit prot mode) */ "movw %%dx, %%ds\n\t" /* count real mode pointer so we don't need to overuse address prefix (by using 32bit addresses in 16bit context) */ "shll $4,%%edx\n\t" "subl %%edx,%%ebx\n\t" /* prepare values to be used after interrupt call */ "pushw %%bx\n\t" "pushw %%ds\n\t" /* fill registers with parameters */ "movw " IR_DS_OFF"(%%bx), %%ax\n\t" "pushw %%ax\n\t" "movl "IR_EAX_OFF"(%%bx), %%eax\n\t" "movl "IR_ECX_OFF"(%%bx), %%ecx\n\t" "movl "IR_EDX_OFF"(%%bx), %%edx\n\t" "movl "IR_EDI_OFF"(%%bx), %%edi\n\t" "movl "IR_ESI_OFF"(%%bx), %%esi\n\t" "movw " IR_ES_OFF"(%%bx), %%es\n\t" "movw " IR_FS_OFF"(%%bx), %%fs\n\t" "movw " IR_GS_OFF"(%%bx), %%gs\n\t" /* prepare ebx register */ "movl "IR_EBX_OFF"(%%bx), %%ebx\n\t" /* prepare ds */ "popw %%ds\n\t" /* interrupt instruction */ ".byte 0xCD\n\t" "intnum: .byte 0x0\n\t" /* fill return structure */ "pushw %%ds\n\t" "pushl %%ebx\n\t" "movw 0x6(%%esp), %%ds\n\t" "movw 0x8(%%esp),%%bx\n\t" /* regs_spot */ "movl %%eax,"IR_EAX_OFF"(%%bx)\n\t" "popl %%eax\n\t" "movl %%eax,"IR_EBX_OFF"(%%bx)\n\t" "movl %%ecx,"IR_ECX_OFF"(%%bx)\n\t" "movl %%edx,"IR_EDX_OFF"(%%bx)\n\t" "movl %%esi,"IR_ESI_OFF"(%%bx)\n\t" "movl %%edi,"IR_EDI_OFF"(%%bx)\n\t" "popw %%ax\n\t" "movw %%ax, " IR_DS_OFF"(%%bx)\n\t" "movw %%es, " IR_ES_OFF"(%%bx)\n\t" "movw %%fs, " IR_FS_OFF"(%%bx)\n\t" "movw %%gs, " IR_GS_OFF"(%%bx)\n\t" /* prepare protected mode data segment */ "movw "BKP_DS_OFF"(%%bx), %%ax\n\t" /* restore protected mode stack values */ "movl "BKP_ESP_OFF"(%%bx),%%esp\n\t" "movw "BKP_SS_OFF"(%%bx), %%dx\n\t" /* return to protected mode */ "movl %%cr0, %%ecx \n\t" "or %[cr0_prot_ena], %%cx\n\t" "movl %%ecx, %%cr0 \n\t" "ljmpl *"PM_ENTRY"(%%bx)\n\t" ".code32\n" /* reload segmentation registers */ "cp_end:" "movw %%ax, %%ds\n\t" /* restore stack segment in protected mode context */ "movw %%dx, %%ss\n\t" "movl %[pm_bkp], %%esi\n\t" "movw "BKP_ES_OFF"(%%esi), %%es\n\t" "movw "BKP_FS_OFF"(%%esi), %%fs\n\t" "movw "BKP_GS_OFF"(%%esi), %%gs\n\t" /* restore IDTR */ "addl $"BKP_IDTR_LIM", %%esi\n\t" "lidt (%%esi)\n\t" : : [regs_spot]"m"(int_passed_regs_spot), [pm_bkp]"m"(pm_bkp_addr), [cr0_prot_ena]"i"(CR0_PROTECTION_ENABLE), [cr0_prot_dis]"i"(~CR0_PROTECTION_ENABLE) : "memory", "ebx", "ecx", "edx", "esi", "edi" ); *ir = int_passed_regs_spot->inoutregs; return 1; }