kern/build: Backports from C template

kernel/GNUmakefile

@@ -22,6 +22,9 @@ $(eval $(call DEFAULT_VAR,KTOOLCHAIN,$(DEFAULT_KTOOLCHAIN)))
 override DEFAULT_KCC := $(KTOOLCHAIN)cc
 $(eval $(call DEFAULT_VAR,KCC,$(DEFAULT_KCC)))
 
+override DEFAULT_KLD := $(KTOOLCHAIN)ld
+$(eval $(call DEFAULT_VAR,KLD,$(DEFAULT_KLD)))
+
 override DEFAULT_KOBJDUMP := $(KTOOLCHAIN)objdump
 $(eval $(call DEFAULT_VAR,KOBJDUMP,$(DEFAULT_KOBJDUMP)))
 
@@ -85,14 +88,13 @@ obj/c/flanterm/backends/fb.c.o: override KCPPFLAGS += \
     -DFLANTERM_FB_DISABLE_BUMP_ALLOC
 
 override KLDFLAGS += \
+    -m elf_x86_64 \
     -nostdlib \
-    -Wl,-m,elf_x86_64 \
-    -Wl,-nostdlib \
-    -Wl,-pie \
-    -Wl,-z,text \
-    -Wl,-z,max-page-size=0x1000 \
-    -Wl,-T,linker.ld \
-    -Wl,-gc-sections
+    -pie \
+    -z text \
+    -z max-page-size=0x1000 \
+    -T linker.ld \
+    -gc-sections
 
 override KVFLAGS += \
     -os vinix \
@@ -126,11 +128,11 @@ all: bin/$(KERNEL)
 # See https://sourceware.org/bugzilla/show_bug.cgi?id=31795 for more information.
 bin/$(KERNEL): GNUmakefile linker.ld obj/blob.c.o $(OBJ)
 	mkdir -p "$$(dirname $@)"
-	$(KCC) $(KCFLAGS) obj/blob.c.o $(OBJ) $(KLDFLAGS) -o $@
+	$(KLD) obj/blob.c.o $(OBJ) $(KLDFLAGS) -o $@
 	mv c/symbol_table.c symbol_table.c.tmp
 	./gensyms.sh $(KOBJDUMP) $@ > c/symbol_table.c
 	$(KCC) $(KCFLAGS) $(KCPPFLAGS) -c c/symbol_table.c -o obj/c/symbol_table.c.o
-	$(KCC) $(KCFLAGS) obj/blob.c.o $(OBJ) $(KLDFLAGS) -o $@
+	$(KLD) obj/blob.c.o $(OBJ) $(KLDFLAGS) -o $@
 	mv symbol_table.c.tmp c/symbol_table.c
 	printf '\003' | dd of=$@ bs=1 count=1 seek=16 conv=notrunc 2>/dev/null
 

kernel/linker.ld

@@ -1,7 +1,7 @@
 /*
  * linker.ld: Linker script of the kernel.
  * Code is governed by the GPL-2.0 license.
- * Copyright (C) 2021-2022 The Vinix authors.
+ * Copyright (C) 2021-2024 The Vinix authors.
  */
 
 /* Tell the linker that we want an x86_64 ELF64 output file */
@@ -11,6 +11,18 @@ OUTPUT_ARCH(i386:x86-64)
 /* We want the symbol main__kmain to be our entry point */
 ENTRY(main__kmain)
 
+/* Define the program headers we want so the bootloader gives us the right */
+/* MMU permissions; this also allows us to exert more control over the linking */
+/* process. */
+PHDRS
+{
+    headers PT_PHDR PHDRS;
+    text    PT_LOAD FILEHDR PHDRS;
+    rodata  PT_LOAD;
+    data    PT_LOAD;
+    dynamic PT_DYNAMIC;
+}
+
 SECTIONS
 {
     /* We want to be placed in the topmost 2GiB of the address space, for optimisations */
@@ -21,52 +33,61 @@ SECTIONS
     /* base load address. */
     . = 0xffffffff80000000 + SIZEOF_HEADERS;
 
-    rodata_start = . - SIZEOF_HEADERS;
+    text_start = . - SIZEOF_HEADERS;
 
-    .rodata ALIGN(CONSTANT(MAXPAGESIZE)) : {
-        *(.rodata .rodata.*)
-    }
+    .text : {
+        *(.text .text.*)
+    } :text
 
-    .text ALIGN(CONSTANT(MAXPAGESIZE)) : {
-        rodata_end = .;
-        text_start = .;
+    /* Move to the next memory page for .rodata */
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
 
-        *(.text .text.*)
-    }
+    text_end = .;
+    rodata_start = .;
+
+    .rodata : {
+        *(.rodata .rodata.*)
+    } :rodata
+
+    /* Move to the next memory page for .data */
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
 
-    .data ALIGN(CONSTANT(MAXPAGESIZE)) : {
-        text_end = .;
-        data_start = .;
+    rodata_end = .;
+    data_start = .;
 
+    .data : {
         *(.data .data.*)
 
         /* Place the sections that contain the Limine requests as part of the .data */
         /* output section. */
         KEEP(*(.requests_start_marker))
         KEEP(*(.requests))
         KEEP(*(.requests_end_marker))
-    }
+    } :data
 
-    /* Dynamic section for relocations and other PIE related information. */
+    /* 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 the data PHDR, otherwise lots of */
+    /* 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 */
     /* above this. */
-    .bss ALIGN(CONSTANT(MAXPAGESIZE)) : {
+    .bss : {
         *(.bss .bss.*)
         *(COMMON)
-    }
+    } :data
 
     data_end = .;
 
-    /* Discard the program interpreter section since we do not need one. This is */
+    /* Discard .note.* and .eh_frame* since they may cause issues on some hosts. */
+    /* Also discard the program interpreter section since we do not need one. This is */
     /* more or less equivalent to the --no-dynamic-linker linker flag, except that it */
     /* works with ld.gold. */
     /DISCARD/ : {
+        *(.eh_frame*)
+        *(.note .note.*)
         *(.interp)
     }
 }