From 9af5588c30c4126a2800aae1afcb0de2c373dc6c Mon Sep 17 00:00:00 2001
From: Benji Dial <benji@benjidial.net>
Date: Mon, 20 May 2024 17:40:47 -0400
Subject: rewrite application stuff in the kernel to support multitasking

---
 kernel/source/load-app.cpp | 153 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 kernel/source/load-app.cpp

(limited to 'kernel/source/load-app.cpp')

diff --git a/kernel/source/load-app.cpp b/kernel/source/load-app.cpp
new file mode 100644
index 0000000..b4ffe03
--- /dev/null
+++ b/kernel/source/load-app.cpp
@@ -0,0 +1,153 @@
+#include <hilbert/kernel/load-app.hpp>
+#include <hilbert/kernel/paging.hpp>
+
+namespace hilbert::kernel {
+
+  struct elf_header {
+    uint8_t fixed[24];
+    uint64_t entry_point;
+    uint64_t program_header_offset;
+    uint64_t section_header_offset;
+    uint32_t flags;
+    uint16_t elf_header_length;
+    uint16_t program_header_pitch;
+    uint16_t program_header_count;
+  };
+
+  struct program_header {
+    uint32_t type;
+    uint32_t flags;
+    uint64_t foffset;
+    uint64_t vaddr;
+    uint64_t paddr;
+    uint64_t flength;
+    uint64_t vlength;
+  };
+
+  struct load_info {
+    uint64_t vaddr;
+    uint64_t vpages_start;
+    uint64_t vpages_count;
+    uint64_t foffset;
+    uint64_t flength;
+    bool writable;
+    bool executable;
+  };
+
+  static uint8_t expected_fixed_header[24] = {
+    0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x02, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00
+  };
+
+  load_app_result load_app(
+    vfile::vfile &file, app_memory &into, uint64_t &entry_out) {
+
+    if (file.dir_entry.type != storage::file_type::regular_file)
+      return load_app_result::not_app;
+
+    if (file.dir_entry.length < sizeof(elf_header))
+      return load_app_result::not_app;
+
+    elf_header eh;
+    if (file.read_file(0, sizeof(elf_header), &eh)
+        != storage::fs_result::success)
+      return load_app_result::io_error;
+
+    for (int i = 0; i < 24; ++i)
+      if (eh.fixed[i] != expected_fixed_header[i])
+        return load_app_result::not_app;
+
+    if (eh.entry_point < 0x1000 || eh.entry_point >= 0x4000000000)
+      return load_app_result::not_app;
+
+    utility::vector<load_info> load_infos;
+
+    for (int i = 0; i < eh.program_header_count; ++i) {
+
+      uint64_t offset = eh.program_header_offset + eh.program_header_pitch * i;
+      if (offset + sizeof(program_header) > file.dir_entry.length)
+        return load_app_result::not_app;
+
+      program_header ph;
+      if (file.read_file(offset, sizeof(program_header), &ph)
+          != storage::fs_result::success)
+        return load_app_result::io_error;
+
+      if (ph.type == 1) {
+
+        uint64_t vpages_start = (ph.vaddr / 4096) * 4096;
+        uint64_t vpages_end = ((ph.vaddr + ph.vlength - 1) / 4096 + 1) * 4096;
+
+        if (vpages_start < 0x1000 || vpages_end >= 0x4000000000 ||
+            ph.foffset + ph.flength > file.dir_entry.length)
+          return load_app_result::not_app;
+
+        load_infos.add_end((load_info){
+          .vaddr = ph.vaddr,
+          .vpages_start = vpages_start,
+          .vpages_count = (vpages_end - vpages_start) / 4096,
+          .foffset = ph.foffset,
+          .flength = ph.flength,
+          .writable = (ph.flags & 2) != 0,
+          .executable = (ph.flags & 4) != 0 });
+
+      }
+
+    }
+
+    for (unsigned i = 0; i < load_infos.count; ++i) {
+      const auto &li = load_infos.buffer[i];
+
+      for (uint64_t pi = 0; pi < li.vpages_count; ++pi) {
+
+        uint64_t page_user_vaddr = li.vpages_start + pi * 4096;
+
+        uint64_t page_kernel_vaddr;
+        uint64_t page_paddr;
+        paging::map_new_kernel_page(page_kernel_vaddr, page_paddr);
+
+        uint8_t *ptr = (uint8_t *)page_kernel_vaddr;
+        int bytes_left = 4096;
+        int64_t foffset = page_user_vaddr - li.vaddr;
+
+        if (foffset < 0) {
+          int to_skip = -foffset;
+          for (int i = 0; i < to_skip; ++i)
+            ptr[i] = 0;
+          ptr += to_skip;
+          bytes_left -= to_skip;
+          foffset = 0;
+        }
+
+        int64_t left_in_file = li.flength - foffset;
+        if (left_in_file > 0) {
+          int to_read = left_in_file < bytes_left ? left_in_file : bytes_left;
+          if (file.read_file(li.foffset + foffset, to_read, ptr) !=
+              storage::fs_result::success) {
+            paging::unmap_kernel_page((uint64_t)page_kernel_vaddr);
+            paging::free_pram_page(page_paddr);
+            return load_app_result::io_error;
+          }
+          ptr += to_read;
+          bytes_left -= to_read;
+        }
+
+        if (bytes_left > 0)
+          for (int i = 0; i < bytes_left; ++i)
+            ptr[i] = 0;
+
+        paging::unmap_kernel_page((uint64_t)page_kernel_vaddr);
+        into.map_page(
+          page_user_vaddr, page_paddr, li.writable, li.executable, true);
+
+      }
+
+    }
+
+    entry_out = eh.entry_point;
+    return load_app_result::success;
+
+  }
+
+}
-- 
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