Lecture 99 - Implementing Elf Loader - Part 6

src/loader/formats/elfloader.c

@@ -73,6 +73,12 @@ struct elf32_shdr* elf_section(struct elf_header* header, int index)
     return &elf_sheader(header)[index];
 }
 
+
+void* elf_phdr_phys_address(struct elf_file* file, struct elf32_phdr* phdr)
+{
+    return elf_memory(file)+phdr->p_offset;
+}
+
 char* elf_str_table(struct elf_header* header)
 {
     return (char*) header + elf_section(header, header->e_shstrndx)->sh_offset;

src/loader/formats/elfloader.h

@@ -48,4 +48,12 @@ void* elf_virtual_end(struct elf_file* file);
 void* elf_phys_base(struct elf_file* file);
 void* elf_phys_end(struct elf_file* file);
 
+struct elf_header* elf_header(struct elf_file* file);
+struct elf32_shdr* elf_sheader(struct elf_header* header);
+void* elf_memory(struct elf_file* file);
+struct elf32_phdr* elf_pheader(struct elf_header* header);
+struct elf32_phdr* elf_program_header(struct elf_header* header, int index);
+struct elf32_shdr* elf_section(struct elf_header* header, int index);
+void* elf_phdr_phys_address(struct elf_file* file, struct elf32_phdr* phdr);
+
 #endif

src/task/process.c

@@ -119,7 +119,23 @@ static int process_map_elf(struct process* process)
     int res = 0;
 
     struct elf_file* elf_file = process->elf_file;
-    res = paging_map_to(process->task->page_directory, paging_align_to_lower_page(elf_virtual_base(elf_file)), elf_phys_base(elf_file), paging_align_address(elf_phys_end(elf_file)), PAGING_IS_PRESENT | PAGING_ACCESS_FROM_ALL | PAGING_IS_WRITEABLE);
+    struct elf_header* header = elf_header(elf_file);
+    struct elf32_phdr* phdrs = elf_pheader(header);
+    for (int i = 0; i < header->e_phnum; i++)
+    {
+        struct elf32_phdr* phdr = &phdrs[i];
+        void* phdr_phys_address = elf_phdr_phys_address(elf_file, phdr);
+        int flags = PAGING_IS_PRESENT | PAGING_ACCESS_FROM_ALL;
+        if (phdr->p_flags & PF_W)
+        {
+            flags |= PAGING_IS_WRITEABLE;
+        }
+        res = paging_map_to(process->task->page_directory, paging_align_to_lower_page((void*)phdr->p_vaddr), paging_align_to_lower_page(phdr_phys_address), paging_align_address(phdr_phys_address+phdr->p_filesz), flags);
+        if (ISERR(res))
+        {
+            break;
+        }
+    }
     return res;
 }
 int process_map_memory(struct process* process)

src/task/task.c

@@ -6,6 +6,7 @@
 #include "memory/memory.h"
 #include "string/string.h"
 #include "memory/paging/paging.h"
+#include "loader/formats/elfloader.h"
 #include "idt/idt.h"
 
 // The current task that is running
@@ -208,6 +209,11 @@ int task_init(struct task *task, struct process *process)
     }
 
     task->registers.ip = PEACHOS_PROGRAM_VIRTUAL_ADDRESS;
+    if (process->filetype == PROCESS_FILETYPE_ELF)
+    {
+        task->registers.ip = elf_header(process->elf_file)->e_entry;
+    }
+
     task->registers.ss = USER_DATA_SEGMENT;
     task->registers.cs = USER_CODE_SEGMENT;
     task->registers.esp = PEACHOS_PROGRAM_VIRTUAL_STACK_ADDRESS_START;