memory allocation

common.h

@@ -19,6 +19,7 @@ typedef uint32_t vaddr_t;
 #define va_start  __builtin_va_start
 #define va_end    __builtin_va_end
 #define va_arg    __builtin_va_arg
+#define PAGE_SIZE 4096
 
 void *memset(void *buf, char c, size_t n);
 void *memcpy(void *dst, const void *src, size_t n);

kernel.c

@@ -2,6 +2,7 @@
 #include "common.h"
 
 extern char __bss[], __bss_end[], __stack_top[];
+extern char __free_ram[], __free_ram_end[];
 
 struct sbiret sbi_call(long arg0, long arg1, long arg2, long arg3, long arg4,
                        long arg5, long fid, long eid) {
@@ -22,6 +23,18 @@ 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 */);
 }
@@ -121,9 +134,16 @@ void kernel_main(void) {
     // }
 
     memset(__bss, 0, (size_t) __bss_end - (size_t) __bss);
+    
+    paddr_t paddr0 = alloc_pages(2);
+    paddr_t paddr1 = alloc_pages(1);
+    printf("alloc_pages test paddr0=%x\n", paddr0);
+    printf("alloc_pages test paddr1=%x\n", paddr1);
 
-    WRITE_CSR(stvec, (uint32_t) kernel_entry);
-    __asm__ __volatile__("unimp");
+    PANIC("You booted successfully :3");
+
+    // WRITE_CSR(stvec, (uint32_t) kernel_entry);
+    // __asm__ __volatile__("unimp"); // calls a unimp which triggers kernel panic
     
     //
     // PANIC("BOOOO!!! GET INFECTED WITH BOOTKID YOU SKID! 0x1337h@x0r");

kernel.ld

@@ -26,4 +26,8 @@ SECTIONS {
     . += 128 * 1024; /* 128KB */
     __stack_top = .;
 
+    . = ALIGN(4096);
+    __free_ram = .;
+    . += 128 * 1024 * 1048; /* 128MB */
+    __free_ram_end = .;
 }