Moved initial usermode program from usermode.c to a separate binary g…

…enerate from um.S and um.ld. Later, embed the binary into boot32.

README.md

@@ -6,6 +6,10 @@ It supports boot loader, kernel with protected mode, paging, E820 enumeration, i
 cat krnlconst.hdr | awk 'BEGIN{print "#ifndef _KERNEL_CONST_H"};{print "#define " $1 " " $2};END{print "#endif";}' > krnlconst.h<br>
 cat krnlconst.hdr | awk '{print ".equ " $1 ", " $2};' > krnlconst.S<br>
 
+as --32 um.S -o um.o<br>
+ld --static -T um.ld -m elf_i386 -nostdlib --nmagic -o um.elf um.o<br>
+objcopy -O binary um.elf um.bin<br>
+
 as --32 mpinit.S -o mpinit.o<br>
 ld -static -T mpinit.ld -m elf_i386 -nostdlib --nmagic -o mpinit.elf mpinit.o<br>
 objcopy -O binary mpinit.elf mpinit.bin<br>

boot32.S

@@ -70,15 +70,24 @@ highaddress:
 loop:
  jmp loop
 
+ // load smp binary code here
  .section mp_init, "ax"
  .global init_ap
  .align 8
 init_ap:
  .incbin "mpinit.bin"
 
  .global init_ap_size
- .align 8
- .global init_ap_size
-
 init_ap_size:
  .int init_ap_size - init_ap
+
+ // load um binary code here
+ .section um_init, "ax"
+ .global init_um
+ .align 4096
+init_um:
+ .incbin "um.bin"
+
+ .global init_um_size
+init_um_size:
+ .int init_um_size - init_um

kernel32.ld

@@ -9,7 +9,8 @@ SECTIONS
  .text : {*(.text); }
  .data : {*(.data); }
  .bss : {*(.bss); }
- um_size = SIZEOF(um);
+ . = ALIGN(8);
+ .um_init : {*(.um_init); }
  . = ALIGN(8);
  .mp_init : {*(.mp_init); }
  . = ALIGN(4096);

start.c

@@ -35,7 +35,6 @@ int start_kernel(void) {
  bda_read_table();
  acpi_init();
  ioapic_init();
- usermode_load_first_program();
  smp_start();
  initialize_usermode();
  switch_to_um();

um.S

@@ -0,0 +1,32 @@
+/*****************************************************************************/
+/* File: um.S */
+/* */
+/* Description: Usermode code. */
+/* */
+/* Author: Shoily O Rahman <[email protected]> */
+/* */
+/* Date: Jun 20, 2021 */
+/* */
+/*****************************************************************************/
+
+ .code32
+ .text
+
+.globl _um_start
+_um_start:
+
+ push %ebp
+ mov %esp,%ebp
+ sub $0x4,%esp
+ movl $0x1,-0x4(%ebp)
+loop:
+ int $0x80
+ mov -0x4(%ebp),%eax
+ inc %eax
+ mov %eax,-0x4(%ebp)
+ jmp loop
+ nop
+ leave
+ ret 
+
+

um.ld

@@ -0,0 +1,34 @@
+/*****************************************************************************/
+/* File: mpinit.ld */
+/* */
+/* Description: ld script file for initializing multiple (application) */
+/* processors. */
+/* */
+/* Author: Shoily O Rahman <[email protected]> */
+/* */
+/* Date: Oct 7, 2020 */
+/* */
+/*****************************************************************************/
+
+OUTPUT_FORMAT(elf32-i386)
+OUTPUT_ARCH(i386)
+
+/* This will overwrite default boot sector */
+ENTRY(_um_start)
+
+PHDRS {
+ text PT_LOAD FILEHDR PHDRS;
+ data PT_LOAD;
+ bss PT_LOAD;
+}
+
+SECTIONS
+{
+ . = 0x10000000;
+ .text :
+ {*(.text); } : text
+ .data :
+ {*(.data); } : data
+ .bss :
+ {*(.bss); } : bss
+}

usermode.c

@@ -15,38 +15,17 @@
 #include "page32.h"
 #include "setup32.h"
 #include "system.h"
+#include "debug.h"
 
 char __attribute__((aligned(4096))) um_pg_table[MAX_NUM_SMPS][PAGE_SIZE];
-char __attribute__((aligned(4096))) user_mode_program[PAGE_SIZE];
 
 #define USER_MODE_STACK_SIZE 8192
 char __attribute__((aligned(8))) user_mode_stack[MAX_NUM_SMPS][USER_MODE_STACK_SIZE];
 
-extern int um, um_size;
 extern int _kernel_pg_dir;
 
-__attribute__((section("um"))) __attribute__((aligned(4096))) void test_usermode_func() {
- int *a = (int*)((char*) USER_MODE_VIRT_TEXT + 0x100);
- int i = 1;
-
- __asm__ __volatile__("int $128;" : : :);
- *a = i++;
-
- __asm__ __volatile("movl %0, %%ecx; jmp *%%ecx;" : : "i" (USER_MODE_VIRT_TEXT+0x16): "%ecx");
-}
-
-void usermode_load_first_program() {
-
- char *s = (char *)test_usermode_func;
- char *d = user_mode_program;
- int i;
-
- memset(user_mode_program, sizeof(user_mode_program), 0);
-
- for(i=(int)&um;i<(int)&um+(int)&um_size;i++) {
- *d++ = *s++;
- }
-}
+extern int init_um;
+extern int init_um_size;
 
 void switch_to_um() {
 
@@ -79,12 +58,12 @@ void initialize_usermode() {
  memset(&user_mode_stack[CUR_CPU][0], USER_MODE_STACK_SIZE, 0);
 
  pgtable[0] = (pte_t*)&um_pg_table[CUR_CPU][0];
- 
+
  build_pagetable((pgd_t*)((int)&_kernel_pg_dir + (PAGE_SIZE*CUR_CPU)),
  pgtable,
- (int)user_mode_program-KERNEL_VIRT_ADDR,
+ (int)&init_um-KERNEL_VIRT_ADDR,
  USER_MODE_VIRT_TEXT,
- (int)&um_size,
+ (int)init_um_size,
  PGD_PRESENT | PGD_WRITE | PGD_USER, PTE_PRESENT | PTE_WRITE | PTE_USER);
 
  build_pagetable((pgd_t*)((int)&_kernel_pg_dir + (PAGE_SIZE*CUR_CPU)),

usermode.h

@@ -15,7 +15,6 @@
 #define USER_MODE_VIRT_TEXT 0x10000000
 #define USER_MODE_VIRT_STACK 0x10003000
 
-void usermode_load_first_program();
 void initialize_usermode();
 void switch_to_um();