Register arguments can be passed to v86 code

dosfs/dosfs.c

@@ -11,19 +11,7 @@
 #include "dosfs.h"
 #include "tmpstring.c"
 #include "../interrupt.h"
-
+#include "../v86defs.h"
-struct __attribute((__packed__)) Int13DiskPacket_t {
-    uint8_t size; // 0x10
-    uint8_t reserved; // 0x00
-    uint16_t blocks;
-    uint32_t transfer_buffer; // 0x2300:0000
-    uint64_t start_block;
-};
-
-extern struct Int13DiskPacket_t v86disk_addr_packet;
-
-extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
-extern void v86DiskRead();
 
 // all reading at 0x23000 - be careful!
 uint32_t DFS_ReadSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count) {
@@ -32,8 +20,9 @@ uint32_t DFS_ReadSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t
 	v86disk_addr_packet.transfer_buffer =
 		(uintptr_t)buffer & 0x000F |
 		(((uintptr_t)buffer & 0xFFFF0) << 12);
+	union V86Regs_t regs;
     FARPTR v86_entry = i386LinearToFp(v86DiskRead);
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
 	return 0;
 }
 uint32_t DFS_WriteSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count) {

fault.nasm

@@ -40,7 +40,7 @@ extern get_key
 extern task_ptr
 extern _enter_v86_internal_no_task
 extern return_prev_task
-extern v86GfxMode
+extern v86VideoInt
 gpf_handler_32:
 push eax
 mov eax, dword [esp+8] ; EIP
@@ -56,19 +56,23 @@ cmp al, 0x00 ; get key
 jne .s1
 call get_key
 jmp .return_to_offender
-.s1: cmp al, 0x10 ; set video mode
+.s1: cmp al, 0x10 ; video interrupt
 jne .return_to_offender
 add esp, 4
 add dword [esp+0], 2
 ; add a new task
 call _gpf_create_return_task
 ; now enter v86 mode
-; push args
+; get regs from return stack
-mov eax, v86GfxMode
+mov eax, [esp+12] ; return esp
+mov eax, [eax] ; regs
+push eax ; regs
+mov eax, v86VideoInt
 and eax, 0xffff
 push eax ; ip
-mov eax, v86GfxMode
+mov eax, v86VideoInt
-shr eax, 16
+shr eax, 4
+and eax, 0xf000
 push eax ; cs
 push 0xFF00 ; sp
 push 0x8000 ; ss

interrupt.c

@@ -51,7 +51,7 @@ FARPTR i386LinearToFp(void *ptr)
 {
     unsigned seg, off;
     off = (uintptr_t) ptr & 0xffff;
-    seg = ((uintptr_t) ptr >> 16);
+    seg = ((uintptr_t) ptr >> 4) & 0xf000;
     return MK_FP(seg, off);
 }
 

kernel.c

@@ -5,6 +5,7 @@
 #include "interrupt.h"
 #include "tss.h"
 #include "paging.h"
+#include "v86defs.h"
 
 typedef unsigned short word;
 
@@ -53,22 +54,6 @@ uint32_t get_cr4() {
     return reg;
 }
 
-struct __attribute((__packed__)) Int13DiskPacket_t {
-    uint8_t size; // 0x10
-    uint8_t reserved; // 0x00
-    uint16_t blocks;
-    uint32_t transfer_buffer; // 0x2300:0000
-    uint64_t start_block;
-};
-
-extern struct Int13DiskPacket_t v86disk_addr_packet;
-
-extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
-extern void v86Test();
-extern void v86TransFlag();
-extern void v86GfxMode();
-extern void v86TextMode();
-extern void v86DiskRead();
 extern char *jmp_usermode_test();
 
 extern char _edata, _v86code, _ev86code, _bstart, _bend, _loadusercode, _usercode, _eusercode;
@@ -119,8 +104,9 @@ void ensure_v86env() {
 
 void error_environment() {
     ensure_v86env();
+    union V86Regs_t regs;
     FARPTR v86_entry = i386LinearToFp(v86TextMode);
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
     printStr("Oh noes!!! System error! ;c    Press E for a fun recovery :3", &error_screen[80]);
     uint16_t *vga_text = ((uint16_t*)0xB8000);
     for (int i = 0; i < 80*50; i++)
@@ -128,7 +114,7 @@ void error_environment() {
     uint8_t key;
     for (key = get_key(); key != 'e' && key != 'E'; key = get_key());
     v86_entry = i386LinearToFp(v86TransFlag);
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
 }
 
 /*
@@ -136,8 +122,8 @@ Real Mode Accessible (First MB)
  00000 -  00400 IVT (1kB)
  00400 -  01000 Unused (3kB)
  01000 -  04000 Free (12kB)
- 04000 -  07C00 Free (15kB)
+ 04000 -  07C00 V86 Code (15kB)
- 07C00 -  08000 Boot (512B)
+ 07C00 -  08000 Boot & V86 Code (512B)
  08000 -  20000 V86 Code (96kB)
  20000 -  30000 Disk Buffer (64kB)
  30000 -  80000 Free (320kB)
@@ -158,8 +144,15 @@ Protected Only (1MB+)
 */
 
 void TestV86() {
+    union V86Regs_t regs;
+    regs.d.edi = 0x11111111;
+    regs.d.esi = 0x22222222;
+    regs.d.ebx = 0x33333333;
+    regs.d.edx = 0x44444444;
+    regs.d.ecx = 0x55555555;
+    regs.d.eax = 0x66666666;
     FARPTR v86_entry = i386LinearToFp(v86Test);
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
 }
 void TestUser() {
     char *vga = jmp_usermode_test();
@@ -168,13 +161,15 @@ void TestUser() {
     }
 }
 void TestDiskRead() {
+    union V86Regs_t regs;
     word *vga_text = (word *)0xb8000 + (80*5);
     vga_text += printStr("Setting Text Mode... ", vga_text);
-    FARPTR v86_entry = i386LinearToFp(v86TextMode);
+    regs.w.ax = 3; // text mode
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    FARPTR v86_entry = i386LinearToFp(v86VideoInt);
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
     vga_text += printStr("Done. Starting Disk Read... ", vga_text);
     v86_entry = i386LinearToFp(v86DiskRead);
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
     vga_text = (word *)0xb8000;
     char *diskReadBuf = (char *)0x23000;
     for (int i = 0; i < (80*25)/2; i++) {

link.ld

@@ -15,7 +15,7 @@ SECTIONS {
         _edata = .;
     }
 
-    .realmode 0x8000 :
+    .realmode 0x4000 :
         AT ( ADDR(.data) + SIZEOF(.data) )
         { _v86code = .; *(.v86); _ev86code = .; }
 

task.nasm

@@ -89,7 +89,7 @@ mov ds, ax
 mov eax, ecx ; restore return value
 iret
 
-; extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
+; extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip, union V86Regs_t *regs);
 global enter_v86
 global _enter_v86_internal_no_task
 enter_v86:
@@ -98,6 +98,17 @@ mov ecx, esp ; return stack
 call save_current_task
 _enter_v86_internal_no_task:
 mov ebp, esp               ; save stack pointer
+mov eax, dword [ebp+16] ; regs
+test eax, eax
+jz .no_regs
+; load regs: edi, esi, ebx, edx, ecx, eax
+mov edi, dword [eax+0]
+mov esi, dword [eax+4]
+mov ebx, dword [eax+8]
+mov edx, dword [eax+12]
+mov ecx, dword [eax+16]
+mov eax, dword [eax+20]
+.no_regs:
 push dword  [ebp+0]        ; ss
 push dword  [ebp+4]        ; esp
 pushfd                     ; eflags

usermode.nasm

@@ -8,7 +8,14 @@ mov dword [0xb800C], 0x0f000f00 | 'd' | 'e' << 16
 mov word [0xb8010], 0x0f00 | '!'
 mov eax, 0 ; command = 00, get key
 int 0x21 ; OS call
-mov eax, 0x00030010 ; command = 10, set video mode 3
+push 0x00000013 ; eax  AH=0,AL=3 set video mode 3
+push 0x00000000 ; ecx
+push 0x00000000 ; edx
+push 0x00000000 ; ebx
+push 0x00000000 ; esi
+push 0x00000000 ; edi
+push esp ; regs
+mov eax, 0x10 ; command = 10
 int 0x21 ; OS call
 mov edi, 0xA0000
 xor eax, eax

v86.nasm

@@ -84,6 +84,12 @@ int 0x10
 int 0x30
 jmp $
 
+global v86VideoInt
+v86VideoInt:
+int 0x10
+int 0x30
+jmp $
+
 global v86DiskRead
 v86DiskRead:
 xor ax, ax ; TODO fix assuming we're in first 64k

v86defs.h

@@ -0,0 +1,51 @@
+#include <stdint.h>
+
+extern void v86Test();
+extern void v86TransFlag();
+extern void v86GfxMode();
+extern void v86TextMode();
+extern void v86DiskRead();
+extern void v86VideoInt();
+
+union __attribute((__packed__)) V86Regs_t {
+    struct dword_regs { 
+        uint32_t edi;
+        uint32_t esi;
+        uint32_t ebx;
+        uint32_t edx;
+        uint32_t ecx;
+        uint32_t eax;
+    } d;
+    struct word_regs { 
+        uint16_t di, _upper_di;
+        uint16_t si, _upper_si;
+        uint16_t bx, _upper_bx;
+        uint16_t dx, _upper_dx;
+        uint16_t cx, _upper_cx;
+        uint16_t ax, _upper_ax;
+    } w;
+    struct byte_regs { 
+        uint16_t di, _upper_di;
+        uint16_t si, _upper_si;
+        uint8_t bl, bh;
+        uint16_t _upper_bx;
+        uint8_t dl, dh;
+        uint16_t _upper_dx;
+        uint8_t cl, ch;
+        uint16_t _upper_cx;
+        uint8_t al, ah;
+        uint16_t _upper_ax;
+    } h;
+};
+
+extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip, union V86Regs_t *regs);
+
+struct __attribute((__packed__)) Int13DiskPacket_t {
+    uint8_t size; // 0x10
+    uint8_t reserved; // 0x00
+    uint16_t blocks;
+    uint32_t transfer_buffer; // 0x2300:0000
+    uint64_t start_block;
+};
+
+extern struct Int13DiskPacket_t v86disk_addr_packet;