[rtems commit] i386/shared/realmode_int: real mode interrupt interface
Gedare Bloom
gedare at rtems.org
Thu Nov 20 14:53:05 UTC 2014
Module: rtems
Branch: master
Commit: 586c86c75a2a074ddd1f12763395868ca2e8b65a
Changeset: http://git.rtems.org/rtems/commit/?id=586c86c75a2a074ddd1f12763395868ca2e8b65a
Author: Jan Dolezal <dolezj21 at fel.cvut.cz>
Date: Thu Nov 20 15:00:31 2014 +0100
i386/shared/realmode_int: real mode interrupt interface
---
c/src/lib/libbsp/i386/pc386/Makefile.am | 2 +
c/src/lib/libbsp/i386/pc386/preinstall.am | 4 +
.../libbsp/i386/shared/realmode_int/realmode_int.c | 406 +++++++++++++++++++++
.../libbsp/i386/shared/realmode_int/realmode_int.h | 85 +++++
4 files changed, 497 insertions(+)
diff --git a/c/src/lib/libbsp/i386/pc386/Makefile.am b/c/src/lib/libbsp/i386/pc386/Makefile.am
index 23a46da..8c06129 100644
--- a/c/src/lib/libbsp/i386/pc386/Makefile.am
+++ b/c/src/lib/libbsp/i386/pc386/Makefile.am
@@ -28,6 +28,7 @@ SUBDIRS = . tools
include_bsp_HEADERS = ../../i386/shared/irq/irq.h
include_bsp_HEADERS += ../../i386/shared/irq/irq_asm.h
include_bsp_HEADERS += ../../i386/shared/comm/tty_drv.h
+include_bsp_HEADERS += ../../i386/shared/realmode_int/realmode_int.h
include_bsp_HEADERS += ../../shared/include/irq-generic.h
include_bsp_HEADERS += ../../shared/include/irq-info.h
include_bsp_HEADERS += console/rtd316.h
@@ -94,6 +95,7 @@ libbsp_a_SOURCES += console/kbd_parser.c
libbsp_a_SOURCES += console/serial_mouse_config.c
libbsp_a_SOURCES += ../../i386/shared/comm/uart.c
libbsp_a_SOURCES += ../../i386/shared/comm/tty_drv.c
+libbsp_a_SOURCES += ../../i386/shared/realmode_int/realmode_int.c
libbsp_a_SOURCES += ../../shared/console.c
libbsp_a_SOURCES += console/console_select.c
libbsp_a_SOURCES += ../../shared/console_read.c
diff --git a/c/src/lib/libbsp/i386/pc386/preinstall.am b/c/src/lib/libbsp/i386/pc386/preinstall.am
index 825023a..4314f22 100644
--- a/c/src/lib/libbsp/i386/pc386/preinstall.am
+++ b/c/src/lib/libbsp/i386/pc386/preinstall.am
@@ -65,6 +65,10 @@ $(PROJECT_INCLUDE)/bsp/tty_drv.h: ../../i386/shared/comm/tty_drv.h $(PROJECT_INC
$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/bsp/tty_drv.h
PREINSTALL_FILES += $(PROJECT_INCLUDE)/bsp/tty_drv.h
+$(PROJECT_INCLUDE)/bsp/realmode_int.h: ../../i386/shared/realmode_int/realmode_int.h $(PROJECT_INCLUDE)/bsp/$(dirstamp)
+ $(INSTALL_DATA) $< $(PROJECT_INCLUDE)/bsp/realmode_int.h
+PREINSTALL_FILES += $(PROJECT_INCLUDE)/bsp/realmode_int.h
+
$(PROJECT_INCLUDE)/bsp/irq-generic.h: ../../shared/include/irq-generic.h $(PROJECT_INCLUDE)/bsp/$(dirstamp)
$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/bsp/irq-generic.h
PREINSTALL_FILES += $(PROJECT_INCLUDE)/bsp/irq-generic.h
diff --git a/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.c b/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.c
new file mode 100644
index 0000000..0aa71e6
--- /dev/null
+++ b/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.c
@@ -0,0 +1,406 @@
+/*
+ * Realmode interrupt call implementation.
+ *
+ *
+ * Copyright (c) 2014 - CTU in Prague
+ * Jan Doležal ( dolezj21 at 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 <bsp/realmode_int.h>
+#include <string.h>
+#include <rtems/score/cpu.h>
+
+#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"
+
+#define BKP_ESP_OFF "0x20"
+#define BKP_SS_OFF "0x24"
+#define BKP_DS_OFF "0x26"
+#define RM_ENTRY "0x28"
+#define PM_ENTRY "0x2C"
+
+/* parameters, results, backup values accessible in real mode */
+typedef struct {
+ i386_realmode_interrupt_registers inoutregs;
+ uint32_t pm_esp_bkp;
+ uint16_t pm_ss_bkp;
+ uint16_t ds_bkp;
+ uint16_t rm_entry;
+ uint16_t rm_code_segment;
+ uint32_t pm_entry;
+ uint16_t pm_code_selector;
+ /* if modifying update offset definitions as well */
+} RTEMS_COMPILER_PACKED_ATTRIBUTE rm_int_regs_bkp_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"
+/* backup values, pointers/parameters accessible in protected mode */
+typedef struct {
+ uint16_t idtr_lim_bkp;
+ uint32_t idtr_base_bkp;
+ uint16_t es_bkp;
+ uint16_t fs_bkp;
+ uint16_t gs_bkp;
+ uint32_t rml_entry;
+ uint16_t rml_code_selector;
+ uint16_t rml_data_selector;
+ uint16_t rm_stack_segment;
+ uint16_t rm_stack_pointer;
+ 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;
+
+/*
+ * Prepares real-mode like descriptors to be used for switching
+ * to real mode.
+ *
+ * @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 interruptNumber,
+ 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 = interruptNumber;
+ /* 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;
+}
+
diff --git a/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.h b/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.h
new file mode 100644
index 0000000..e5f80d0
--- /dev/null
+++ b/c/src/lib/libbsp/i386/shared/realmode_int/realmode_int.h
@@ -0,0 +1,85 @@
+/**
+ * @file realmode_int.h
+ *
+ * @ingroup i386_shared
+ *
+ * @brief Definitioins supporting real mode interrupt calls.
+ */
+
+/*
+ * Interface allows calling given interrupt number with content of the
+ * registers defined. For passing or receiving higher amounts of the data
+ * there is a buffer accessible from real mode available. Real mode pointer
+ * to this buffer is passed to the interrupt in the registers.
+ *
+ * Copyright (C) 2014 Jan Doležal (dolezj21 at fel.cvut.cz)
+ * CTU in Prague.
+ *
+ * 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.
+ */
+
+#ifndef _REALMODE_INT_H
+#define _REALMODE_INT_H
+
+#include <libcpu/cpu.h>
+#include <stdint.h>
+
+#ifndef ASM /* ASM */
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/* --- BIOS service interrupt number --- */
+/* number of interrupt servicing video functions */
+#define INTERRUPT_NO_VIDEO_SERVICES 0x10
+
+typedef struct { /* used for passing parameters, fetching results and preserving values */
+ uint32_t reg_eax;
+ uint32_t reg_ebx;
+ uint32_t reg_ecx;
+ uint32_t reg_edx;
+ uint32_t reg_esi;
+ uint32_t reg_edi;
+ uint16_t reg_ds;
+ uint16_t reg_es;
+ uint16_t reg_fs;
+ uint16_t reg_gs;
+} RTEMS_COMPILER_PACKED_ATTRIBUTE i386_realmode_interrupt_registers;
+
+/**
+ * Provides position to real mode buffer. It is buffer
+ * accessible from real mode context - it is located below
+ * address ~0x100000 in order for it to be accessible
+ * This buffer is meant to be pointed to by segReg:GenPurpReg
+ * and through this get bigger portion of an information to/from
+ * interrupt service routine than just by using register.
+ *
+ * @param size pointer to variable, where the size of buffer
+ * will be filled
+ * @retval pointer to buffer
+ */
+extern void *i386_get_default_rm_buffer(uint16_t *size);
+
+/**
+ * This function allows calling interrupts in real mode and to set processor
+ * registers as desired before interrupt call is made and to retrieve the
+ * registers content after call was made.
+ *
+ * @param interruptNumber interrupt number to be called
+ * @param ir pointer to structure containing registers to be passed to interrupt
+ * and to retrieve register content after call was made.
+ * @retval 0 call failed (GDT too small or pagin is on)
+ * 1 call successful
+ */
+extern int i386_real_interrupt_call(uint8_t interruptNumber, i386_realmode_interrupt_registers *ir);
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* ASM */
+
+#endif /* _REALMODE_INT_H */
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