map kernel memory area

kernel.c

@@ -1,9 +1,41 @@
 #include "kernel.h"
 #include "common.h"
-#include <sys/types.h>
 
 extern char __bss[], __bss_end[], __stack_top[];
 extern char __free_ram[], __free_ram_end[];
+extern char __kernel_base[];
+
+paddr_t alloc_pages(uint32_t n) {
+    static paddr_t next_paddr = (paddr_t) __free_ram;
+    paddr_t paddr = next_paddr;
+    next_paddr += n * PAGE_SIZE;
+    
+    if (next_paddr > (paddr_t) __free_ram_end)
+        PANIC("Out ow memowy~ :((");
+
+    memset((void *) paddr, 0, n * PAGE_SIZE);
+    return paddr;  
+}
+
+void map_page(uint32_t *table1, uint32_t vaddr, paddr_t paddr, uint32_t flags) {
+    if (!is_aligned(vaddr, PAGE_SIZE))
+        PANIC("Unaligned vaddr %x", vaddr);
+
+    if (!is_aligned(paddr, PAGE_SIZE))
+        PANIC("Unaligned paddr %x", paddr);
+
+    uint32_t vpn1 = (vaddr >> 22) & 0x3ff;
+    if ((table1[vpn1] & PAGE_V) == 0) {
+        // Create the first level page
+        uint32_t pt_paddr = alloc_pages(1);
+        table1[vpn1] = ((pt_paddr / PAGE_SIZE) << 10) | PAGE_V;
+    }
+    
+    // Set the second level page table entry to map the physical page
+    uint32_t vpn0 = (vaddr >> 12) & 0x3ff;
+    uint32_t *table0 = (uint32_t *) ((table1[vpn1] >> 10) * PAGE_SIZE);
+    table0[vpn0] = ((paddr / PAGE_SIZE) << 10) | flags | PAGE_V;
+}
 
 struct sbiret sbi_call(long arg0, long arg1, long arg2, long arg3, long arg4,
                        long arg5, long fid, long eid) {
@@ -24,18 +56,6 @@ struct sbiret sbi_call(long arg0, long arg1, long arg2, long arg3, long arg4,
     return (struct sbiret){.error = a0, .value = a1};
 }
 
-paddr_t alloc_pages(uint32_t n) {
-    static paddr_t next_paddr = (paddr_t) __free_ram;
-    paddr_t paddr = next_paddr;
-    next_paddr += n * PAGE_SIZE;
-    
-    if (next_paddr > (paddr_t) __free_ram_end)
-        PANIC("Out ow memowy~ :((");
-
-    memset((void *) paddr, 0, n * PAGE_SIZE);
-    return paddr;  
-}
-
 void putchar(char ch) {
     sbi_call(ch, 0, 0, 0, 0, 0, 0, 1 /* Console Putchar */);
 }
@@ -204,11 +224,17 @@ struct process *create_process(uint32_t pc) {
     *--sp = 0;                    // s0
     *--sp = (uint32_t) pc;        // ra
     
+    // Map kernel pages
+    uint32_t *page_table = (uint32_t *) alloc_pages(1);
+    for (paddr_t paddr = (paddr_t) __kernel_base; paddr < (paddr_t) __free_ram_end; paddr += PAGE_SIZE) {
+        map_page(page_table, paddr, paddr, PAGE_R | PAGE_W | PAGE_X);
+    }
 
     // Initialize fields
     proc->pid = i + 1;
     proc->state = PROC_RUNNABLE;
     proc->sp = (uint32_t) sp;
+    proc->page_table = page_table;
     return proc;
 }
 
@@ -266,26 +292,6 @@ void proc_b_entry(void) {
     }
 }
 
-void map_page(uint32_t *table1, uint32_t vaddr, paddr_t paddr, uint32_t flags) {
-    if (!is_aligned(vaddr, PAGE_SIZE))
-        PANIC("Unaligned vaddr %x", vaddr);
-
-    if (!is_aligned(paddr, PAGE_SIZE))
-        PANIC("Unaligned paddr %x", paddr);
-
-    uint32_t vpn1 = (vaddr >> 22) & 0x3ff;
-    if ((table1[vpn1] & PAGE_V) == 0) {
-        // Create the first level page
-        uint32_t pt_paddr = alloc_pages(1);
-        table1[vpn1] = ((pt_paddr / PAGE_SIZE) << 10) | PAGE_V;
-    }
-    
-    // Set the second level page table entry to map the physical page
-    uint32_t vpn0 = (vaddr >> 12) & 0x3ff;
-    uint32_t *table0 = (uint32_t *) ((table1[vpn1] >> 10) * PAGE_SIZE);
-    table0[vpn0] = ((paddr / PAGE_SIZE) << 10) | flags | PAGE_V;
-}
-
 void kernel_main(void) {
     // printf("\n\nHello %s\n", "friend :3");
     // printf("60 + 9 = %d, %x\n", 60 + 9, 0x1234abcd);

kernel.h

@@ -64,16 +64,19 @@ struct trap_frame {
 #define PROC_UNUSED 0           // Unused processes control structure
 #define PROC_RUNNABLE 1         // Runnable proccess
 
-struct process {
-    int pid;                    // ID of a process
-    int state;                  // State of the process: either PROC_UNUSED or PROC_RUNNABLE
-    vaddr_t sp;                 // Stack pointer
-    uint8_t stack[8192];        // Kernel stack
-};
-
+// Page table
 #define SATP_SV32 (1u << 32)
 #define PAGE_V (1 << 0) // "Valid" bit (entry is allowed)
 #define PAGE_R (1 << 1) // Readable
 #define PAGE_W (1 << 2) // Writable
 #define PAGE_X (1 << 3) // Executable
 #define PAGE_U (1 << 4) // User (accessible in user mode)
+
+struct process {
+    int pid;                    // ID of a process
+    int state;                  // State of the process: either PROC_UNUSED or PROC_RUNNABLE
+    vaddr_t sp;                 // Stack pointer
+    uint32_t *page_table;
+    uint8_t stack[8192];        // Kernel stack
+};
+

kernel.ld

@@ -2,6 +2,7 @@ ENTRY(BOOT)
 
 SECTIONS {
     . = 0x80200000;
+    __kernel_base = .;
 
     .text :{
         KEEP(*(.text.boot));