Changed the rounding of usable RAM addresses and the freeing of the multiboot2 info...

diff --git a/src/kernel.cpp b/src/kernel.cpp
index 5799f4664ffc4615c0925c98fd26380d7fc4e3a2..32ec362d27b4b8e524df9a588f772af2d1373dc3 100644 (file)
--- a/src/kernel.cpp
+++ b/src/kernel.cpp
@@ -49,8 +49,9 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
                asm("mov $_kernel_phys_end,%0" : "=ri"(ptr));
                return ptr;
        })();
-       const os::phys_ptr<os::paging::page> info_start{info.get_phys_addr()};
-       const os::phys_ptr<os::paging::page> info_end = info_start + (info->total_size - 1 + 0x1000) / 0x1000; // Number of pages taken, rounded up
+       const os::phys_ptr<os::paging::page> info_start{info.get_phys_addr() / 0x1000 * 0x1000}; // Round start down.
+       const os::phys_ptr<os::paging::page> info_end{(info.get_phys_addr() + info->total_size + 0x1000 - 1) / 0x1000 * 0x1000}; // Round end up.
+       bool info_pages_wholly_usable = false;
 
        os::framebuffer framebuffer;
 
@@ -59,6 +60,11 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
        for (auto it = multiboot2::next(info); it->type != multiboot2::info::type_t::end; it = multiboot2::next(it)) {
                switch (it->type) {
                case multiboot2::info::type_t::framebuffer_info:
+                       os::print("Framebuffer:\n");
+                       os::print(multiboot2::framebuffer_addr(it));
+                       os::print("->");
+                       os::print(multiboot2::framebuffer_addr(it) + multiboot2::framebuffer_pitch(it) * multiboot2::framebuffer_height(it));
+                       os::printc('\n');
                        framebuffer = os::framebuffer(
                                multiboot2::framebuffer_addr(it),
                                multiboot2::framebuffer_pitch(it),
@@ -70,19 +76,14 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
                        );
                        break;
                case multiboot2::info::type_t::memory_map:
-                       os::println("Memory map:");
                        for (std::size_t i = 0; i < multiboot2::memory_map_number_of_entries(it); i++) {
-                               os::print(multiboot2::memory_map_base_addr(it, i));
-                               os::print("->");
-                               os::print(multiboot2::memory_map_base_addr(it, i) + multiboot2::memory_map_length(it, i));
-                               os::printc(':');
-                               os::printc('0' + multiboot2::memory_map_type(it, i));
-                               os::printc('\n');
                                if (multiboot2::memory_map_type(it, i) == 1) {
-                                       const os::phys_ptr<os::paging::page> s{multiboot2::memory_map_base_addr(it, i) == 0 ? 0x1000 : multiboot2::memory_map_base_addr(it, i)};
+                                       const os::phys_ptr<os::paging::page> s{
+                                               multiboot2::memory_map_base_addr(it, i) < 0x1000
+                                                       ? 0x1000
+                                                       : (multiboot2::memory_map_base_addr(it, i) + 0x1000 - 1) / 0x1000 * 0x1000
+                                       };
                                        const os::phys_ptr<os::paging::page> e{multiboot2::memory_map_base_addr(it, i) + multiboot2::memory_map_length(it, i) / 0x1000 * 0x1000};
-                                       if (s == nullptr) {
-                                       }
                                        if (s < e) {
                                                remove_some_mem(
                                                s, e, kernel_start, kernel_end,
@@ -96,6 +97,14 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
                                                }
                                                );
                                        }
+                                       bool info_usable = true;
+                                       remove_some_mem(info_start, info_end, s, e, [&info_usable](auto, auto) {
+                                               info_usable = false;
+                                       });
+                                       info_pages_wholly_usable = info_pages_wholly_usable || info_usable;
+                                       // info_pages_wholly_usable will only be false if no usable RAM section covers all the multiboot info struct.
+                                       // This allows me to make sure that I don't use any unusable RAM, in the very improbable case where the
+                                       // multiboot info struct is in a partially usable memory page.
                                }
                        }
                        break;
@@ -104,9 +113,14 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
        }
 
        // Deallocate multiboot info structure: not usable anymore.
-       page_allocator.deallocate({.ptr = info_start, .size = (info_end.get_phys_addr() - info_start.get_phys_addr()) / 0x1000});
+       if (info_pages_wholly_usable) {
+               page_allocator.deallocate({.ptr = info_start, .size = (info_end.get_phys_addr() - info_start.get_phys_addr()) / 0x1000});
+       } else if (info_start + 1 < info_end - 1) {
+               // Ignore the first and last blocks: ensures all the RAM is truly usable.
+               page_allocator.deallocate({.ptr = info_start + 1, .size = (info_end.get_phys_addr() - info_start.get_phys_addr()) / 0x1000 - 2});
+       }
 
-       os::println("RAM:");
+       os::print("RAM:\n");
        page_allocator.print_all();
 
        for (std::size_t x = 0; x < framebuffer.get_width(); x++) {