Working on stivale

src/lib/elf.c

@@ -59,10 +59,25 @@ struct elf_shdr {
     uint64_t   sh_entsize;
 };
 
-int elf_load_section(struct echfs_file_handle *fd, void *buffer, const char *name) {
+int elf_load_section(struct echfs_file_handle *fd, void *buffer, const char *name, size_t limit) {
     struct elf_hdr hdr;
     echfs_read(fd, &hdr, 0, sizeof(struct elf_hdr));
 
+    if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
+        print("elf: Not a valid ELF file.\n");
+        return 1;
+    }
+
+    if (hdr.ident[EI_DATA] != BITS_LE) {
+        print("elf: Not a Little-endian ELF file.\n");
+        return 1;
+    }
+
+    if (hdr.machine != ARCH_X86_64) {
+        print("elf: Not an x86_64 ELF file.\n");
+        return 1;
+    }
+
     struct elf_shdr shstrtab;
     echfs_read(fd, &shstrtab, hdr.shoff + hdr.shstrndx * sizeof(struct elf_shdr),
             sizeof(struct elf_shdr));
@@ -76,12 +91,14 @@ int elf_load_section(struct echfs_file_handle *fd, void *buffer, const char *nam
                    sizeof(struct elf_shdr));
 
         if (!strcmp(&names[section.sh_name], name)) {
+            if (section.sh_size > limit)
+                return 3;
             echfs_read(fd, buffer, section.sh_offset, section.sh_size);
             return 0;
         }
     }
 
-    return 1;
+    return 2;
 }
 
 #define FIXED_HIGHER_HALF_OFFSET ((uint64_t)0xffffffff80000000)

src/lib/elf.h

@@ -5,6 +5,6 @@
 #include <fs/echfs.h>
 
 int elf_load(struct echfs_file_handle *fd, uint64_t *entry_point);
-int elf_load_section(struct echfs_file_handle *fd, void *buffer, const char *name);
+int elf_load_section(struct echfs_file_handle *fd, void *buffer, const char *name, size_t limit);
 
 #endif

src/protos/stivale.c

@@ -2,16 +2,56 @@
 #include <stddef.h>
 #include <protos/stivale.h>
 #include <lib/elf.h>
+#include <lib/blib.h>
 
 struct stivale_header {
-    uint64_t magic;
     uint64_t stack;
     uint8_t  video_mode;  // 0 = default at boot (CGA text mode). 1 = graphical VESA
-};
+} __attribute__((packed));
+
+struct stivale_module {
+    uint64_t begin;
+    uint64_t end;
+    char     string[128];
+} __attribute__((packed));
+
+struct stivale_struct {
+    char    *cmdline;
+    uint64_t memory_map_addr;
+    uint64_t memory_map_entries;
+    uint64_t framebuffer_addr;
+    uint16_t framebuffer_pitch;
+    uint16_t framebuffer_width;
+    uint16_t framebuffer_height;
+    uint16_t framebuffer_bpp;
+    uint64_t module_count;
+    struct stivale_module modules[];
+} __attribute__((packed));
+
+struct stivale_struct stivale_struct;
 
 void stivale_load(struct echfs_file_handle *fd) {
     uint64_t entry_point;
 
+    struct stivale_header stivale_hdr;
+    int ret = elf_load_section(fd, &stivale_hdr, ".stivalehdr", sizeof(struct stivale_header));
+    switch (ret) {
+        case 1:
+            print("stivale: File is not a valid ELF.\n");
+            for (;;);
+        case 2:
+            print("stivale: Section .stivalehdr not found.\n");
+            for (;;);
+        case 3:
+            print("stivale: Section .stivalehdr exceeds the size of the struct.\n");
+            for (;;);
+        default:
+            break;
+    }
+
+    print("stivale: Requested stack at %X\n", stivale_hdr.stack);
+    print("stivale: Video mode: %u\n", stivale_hdr.video_mode);
+
     elf_load(fd, &entry_point);
 
     volatile struct {
@@ -66,6 +106,6 @@ void stivale_load(struct echfs_file_handle *fd) {
         "jmp [rbx]\n\t"
         ".code32\n\t"
         :
-        : "a" (pagemap), "b" (&entry_point)
+        : "a" (pagemap), "b" (&entry_point), "S" (&stivale_struct)
     );
 }

test/test.asm

@@ -1,7 +1,17 @@
 ; This is a compliant "kernel" meant for testing purposes.
 
 ; Header
+section .stivalehdr
 
+stivale_header:
+    dq stack.top
+    db 0
+
+section .bss
+
+stack:
+    resb 4096
+  .top:
 
 section .text