From 8a9208612eec8ddae4c418485d848ecfa0613699 Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Mon, 30 Oct 2023 22:12:14 +0100
Subject: Meta: Move kernel and userland to their own folders.

This is to allow both the kernel and the userland to share certain
header files and to make the folder structure a bit more clear.
---
 kernel/elf.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 kernel/elf.c

(limited to 'kernel/elf.c')

diff --git a/kernel/elf.c b/kernel/elf.c
new file mode 100644
index 0000000..7316a0c
--- /dev/null
+++ b/kernel/elf.c
@@ -0,0 +1,73 @@
+#include <assert.h>
+#include <crypto/SHA1/sha1.h>
+#include <elf.h>
+#include <sched/scheduler.h>
+#include <stddef.h>
+#include <stdint.h>
+
+void *load_elf_file(const char *f, uint32_t *ds) {
+  //  ELFHeader *header = kmalloc(sizeof(ELFHeader));
+  ELFHeader header;
+  int fd = vfs_open(f, O_RDONLY, 0);
+  if (fd < 0) {
+    return NULL;
+  }
+
+  if (sizeof(header) != vfs_pread(fd, &header, sizeof(header), 0)) {
+    return NULL;
+  }
+
+  if (0 != memcmp(header.e_ident, "\x7F\x45\x4C\x46" /* "\x7FELF" */, 4)) {
+    klog("Incorrect ELF signature", LOG_ERROR);
+    return NULL;
+  }
+
+  if (0 > fd) {
+    return NULL;
+  }
+  Elf32_Phdr program_header;
+  assert(sizeof(program_header) == header.e_phentsize);
+  uint32_t header_offset = header.e_phoff;
+  uintptr_t end_of_code = 0;
+  for (int i = 0; i < header.e_phnum;
+       i++, header_offset += header.e_phentsize) {
+    if (0 >=
+        vfs_pread(fd, &program_header, sizeof(program_header), header_offset)) {
+      return NULL;
+    }
+
+    // FIXME: Only one type is supported, which is 1(load). More should be
+    // added.
+    assert(1 == program_header.p_type);
+
+    // 1. Clear p_memsz bytes at p_vaddr to 0.(We also allocate frames for
+    // that range)
+    uint32_t p_memsz = program_header.p_memsz;
+    uint32_t p_vaddr = program_header.p_vaddr;
+
+    uint32_t pages_to_allocate =
+        (uint32_t)align_page((void *)(p_vaddr + p_memsz));
+    pages_to_allocate -= p_vaddr - (p_vaddr % 0x1000);
+    pages_to_allocate /= 0x1000;
+
+    mmu_allocate_region((void *)p_vaddr, pages_to_allocate * 0x1000,
+                        MMU_FLAG_RW, NULL);
+
+    flush_tlb();
+
+    uintptr_t e = program_header.p_vaddr + program_header.p_memsz;
+    if (e > end_of_code)
+      end_of_code = e;
+
+    memset((void *)program_header.p_vaddr, 0, program_header.p_memsz);
+
+    // 2. Copy p_filesz bytes from p_offset to p_vaddr
+    int rc = vfs_pread(fd, (void *)program_header.p_vaddr,
+                       program_header.p_filesz, program_header.p_offset);
+
+    assert(rc == (int)program_header.p_filesz);
+  }
+  *ds = end_of_code;
+  vfs_close(fd);
+  return (void *)header.e_entry;
+}
-- 
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