working on reading elf from initrd, and getting it launched with the new scheduler

kernel/kmain.c

@@ -4,6 +4,7 @@
 #include "scheduler.h"
 #include "common.h"
 #include "vfs.h"
+#include "elf.h"
 
 #include <lib/print.h>
 #include <lib/stream.h>
@@ -51,26 +52,73 @@ vfs_node_t* load_initrd() {
   return cpio_read_fs(initrd_module->mod_start);
 }
 
-void load_origin_program() {
-  vfs_node_t* vfs_root = vfs_create_root();
-  vfs_node_t* initrd_root = load_initrd();
-  
-  if (initrd_root) {
-    mount(vfs_root, initrd_root);
-    kprintf("initrd read, mounted @ /\n");
+void load_program(const char* path) {
+  void* cr3 = create_task_pd();
+  load_pd(cr3);
+  flush_tlb();
 
-    int fd = open("/origin.elf", 0);
-    if (fd == -1) {
-      kprintf("failed to read origin program\n");
-    }
-
-    void* buf = kalloc(512);
-    int rd = read(fd, buf, 512);
-    if (rd > 0) {
-      kprintf("read %d bytes from origin.elf\n", rd);
-    }
+  int fd = open(path, 0);
+  if (fd == -1) {
+    kprintf("failed to open program: %s\n", path);
+    return;;
   }
-  exit();
+  elf_header_t* e_hdr = kalloc(sizeof(elf_header_t));
+  memset((void*)e_hdr, 0, sizeof(elf_header_t));
+
+  uint32_t bytes_rd = read(fd, e_hdr, sizeof(elf_header_t));
+  if (bytes_rd <= 0) {
+    kprintf("failed to read program data for %s\n", path);
+    return;
+  }
+
+  uint32_t ph_table_ptr = e_hdr->e_phoff;
+  elf_program_header_t* ph = kalloc(sizeof(elf_program_header_t));
+  uint32_t heap_start = 0;
+
+  for (uint32_t i = 0; i < e_hdr->e_phnum; i++) {
+    fseek(fd, ph_table_ptr);
+    memset((void*)ph, 0, sizeof(elf_program_header_t));
+    read(fd, ph, sizeof(elf_program_header_t));
+
+    if (ph->p_type == PT_LOAD) {
+      uint32_t vstart = ph->p_vaddr;
+      uint32_t vend = vstart + ph->p_memsz;
+
+      if (vend > heap_start) {
+        heap_start = vend;
+      }
+
+      uint32_t page_start = vstart & ~(PAGE_SIZE - 1);
+      uint32_t page_end = (vend + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
+
+      for (uint32_t v = page_start; v < page_end; v += PAGE_SIZE) {
+          void* phys_frame = p_alloc_frame();
+          map_page(v, (uint32_t)phys_frame, 0x07);
+      }
+
+      uint32_t data_ptr = ph->p_offset;
+      fseek(fd, data_ptr);
+      read(fd, (void*)vstart, ph->p_memsz);
+
+      // 0 out bss
+      if (ph->p_memsz > ph->p_filesz) {
+        size_t bss_size = ph->p_memsz - ph->p_filesz;
+        memset((void*)(vstart + ph->p_filesz), 0, bss_size);
+      }
+    }
+
+    ph_table_ptr += sizeof(elf_program_header_t);
+  }
+
+  uint32_t esp = 0xBFFF0000;
+  void* pesp = p_alloc_frame();
+  map_page(esp - PAGE_SIZE, (uint32_t)pesp, 0x07);
+
+  create_task(e_hdr->e_entry, fetch_cr3(), 1);
+}
+
+void start_origin() {
+  load_program("/origin.elf");
 }
 
 void kmain(uint32_t magic, multiboot_info* mbi)  {
@@ -96,9 +144,19 @@ void kmain(uint32_t magic, multiboot_info* mbi)  {
   
   kprintf("basic initializations complete\n");
 
+  vfs_node_t* vfs_root = vfs_create_root();
+
+  vfs_node_t* initrd_root = load_initrd();
+  if (!initrd_root) {
+    kprintf("failed to load initrd\n");
+  }
+  mount(vfs_root, initrd_root);
+  kprintf("initrd read, mounted @ /\n");
+
   disable_interrupts();
   init_scheduler();
   enable_interrupts();
 
-  create_task((uint32_t)load_origin_program, fetch_cr3());
+  kprintf("loading user program\n");
+  start_origin();
 }