Make PIE kernel

kernel/GNUmakefile

@@ -50,8 +50,7 @@ override CFLAGS += \
     -fno-stack-protector \
     -fno-stack-check \
     -fno-lto \
-    -fno-PIE \
-    -fno-PIC \
+    -fPIE \
     -m64 \
     -march=x86-64 \
     -mabi=sysv \
@@ -59,8 +58,7 @@ override CFLAGS += \
     -mno-mmx \
     -mno-sse \
     -mno-sse2 \
-    -mno-red-zone \
-    -mcmodel=kernel
+    -mno-red-zone
 
 # Internal C preprocessor flags that should not be changed by the user.
 override CPPFLAGS := \
@@ -71,17 +69,15 @@ override CPPFLAGS := \
 
 # Internal linker flags that should not be changed by the user.
 override LDFLAGS += \
+    -m elf_x86_64 \
     -nostdlib \
     -static \
-    -m elf_x86_64 \
+    -pie \
+    --no-dynamic-linker \
+    -z text \
     -z max-page-size=0x1000 \
     -T linker.ld
 
-# Check if the linker supports -no-pie and enable it if it does.
-ifeq ($(shell $(LD) --help 2>&1 | grep 'no-pie' >/dev/null 2>&1; echo $$?),0)
-    override LDFLAGS += -no-pie
-endif
-
 # Internal nasm flags that should not be changed by the user.
 override NASMFLAGS += \
     -Wall \

kernel/linker.ld

@@ -12,6 +12,7 @@ PHDRS
     text    PT_LOAD    FLAGS((1 << 0) | (1 << 2)) ; /* Execute + Read */
     rodata  PT_LOAD    FLAGS((1 << 2)) ;            /* Read only */
     data    PT_LOAD    FLAGS((1 << 1) | (1 << 2)) ; /* Write + Read */
+    dynamic PT_DYNAMIC FLAGS((1 << 1) | (1 << 2)) ; /* Dynamic PHDR for relocations */
 }
 
 SECTIONS
@@ -40,6 +41,11 @@ SECTIONS
         *(.data .data.*)
     } :data
 
+    /* Dynamic section for relocations, both in its own PHDR and inside data PHDR */
+    .dynamic : {
+        *(.dynamic)
+    } :data :dynamic
+
     /* NOTE: .bss needs to be the last thing mapped to :data, otherwise lots of */
     /* unnecessary zeros will be written to the binary. */
     /* If you need, for example, .init_array and .fini_array, those should be placed */

limine.cfg

@@ -2,9 +2,18 @@
 TIMEOUT=3
 
 # The entry name that will be displayed in the boot menu.
-:Limine Barebones
+:Limine Barebones (KASLR off)
     # We use the Limine boot protocol.
     PROTOCOL=limine
 
+    # Disable KASLR (it is enabled by default for relocatable kernels)
+    KASLR=no
+
     # Path to the kernel to boot. boot:/// represents the partition on which limine.cfg is located.
     KERNEL_PATH=boot:///kernel.elf
+
+# Same thing, but with KASLR.
+:Limine Barebones (KASLR on)
+    PROTOCOL=limine
+
+    KERNEL_PATH=boot:///kernel.elf