Switched to PIE flat binaries

8 files changed, 59 insertions, 127 deletions

diff --git a/Makefile b/Makefile
index 061aafa..7916d68 100644
--- a/Makefile
+++ b/Makefile
@@ -12,22 +12,22 @@ COBJS_KERNEL = src/main.o \
 		src/features/fs.o \
 		src/features/psf.o \
 		src/features/gui.o \
-		src/features/elf.o \
+		src/features/load.o \
 		src/lib/str.o \
 		src/lib/mem.o \
 		src/lib/math.o \
 		src/lib/conv.o \
 		src/lib/print.o
-COBJS_APPS = apps/test.o
-CC = ccache cross/opt/bin/i686-elf-gcc
-LD = ccache cross/opt/bin/i686-elf-ld
-AS = ccache nasm
+CC = cross/opt/bin/i686-elf-gcc
+LD = cross/opt/bin/i686-elf-ld
+OC = cross/opt/bin/i686-elf-objcopy
+AS = nasm
 
 # Flags to make the binary smaller TODO: Remove after indirect pointer support!
 CSFLAGS = -mpreferred-stack-boundary=2 -fno-asynchronous-unwind-tables -Os
 
 # TODO: Use lib as external library
-CFLAGS = $(CSFLAGS) -Wall -Wextra -nostdlib -nostdinc -ffreestanding -fno-builtin -fno-pic -mgeneral-regs-only -std=c99 -m32 -pedantic-errors -Isrc/lib/inc/ -Isrc/inc/
+CFLAGS = $(CSFLAGS) -Wall -Wextra -nostdlib -nostdinc -ffreestanding -fno-builtin -mgeneral-regs-only -std=c99 -m32 -pedantic-errors -Isrc/lib/inc/ -Isrc/inc/
 
 ASFLAGS = -f elf32 -O3
 
@@ -41,14 +41,14 @@ all: compile clean
 
 kernel: $(COBJS_KERNEL)
 
-apps: $(COBJS_APPS)
-
-compile: kernel apps
+compile: kernel
 	@mkdir -p build/
 	@$(AS) -f bin src/entry.asm -o build/boot.bin
 	@$(LD) -N -emain -Ttext 0x00050000 -o build/kernel.bin $(COBJS_KERNEL) --oformat binary
 	@$(CC) $(CFLAGS) -o build/debug.o $(COBJS_KERNEL)
-	@$(LD) -N -emain -Tapps/link.ld -o build/test apps/test.o
+	@$(CC) $(CFLAGS) -fPIE -c apps/test.c -o build/test.o
+	@$(LD) -o build/test.elf -Tapps/link.ld build/test.o
+	@$(OC) -O binary build/test.elf build/test
 
 clean:
 	@find src/ apps/ -name "*.o" -type f -delete
diff --git a/apps/link.ld b/apps/link.ld
index ee41578..14fe1e3 100644
--- a/apps/link.ld
+++ b/apps/link.ld
@@ -1,24 +1,34 @@
-ENTRY(main)
+OUTPUT_FORMAT("elf32-i386")
+OUTPUT_ARCH(i386)
+ENTRY(start)
+
 SECTIONS
 {
-	.text 0x40000000:
-	{
-		code = .; _code = .; __code = .;
+	. = 0x00000000;
+
+	.text : {
 		*(.text)
 	}
 
-	.data ALIGN(0x400000):
-	{
-		data = .; _data = .; __data = .;
-		*(.data)
+	.rodata : {
 		*(.rodata)
 	}
 
-	.bss ALIGN(0x400000):
-	{
-		bss = .; _bss = .; __bss = .;
+	. = ALIGN(4096);
+
+	.data : {
+		*(.data)
+	}
+
+	. = ALIGN(4096);
+
+	.bss : {
 		*(.bss)
 	}
 
-	end = .; _end = .; __end = .;
+	. = ALIGN(4096);
+
+	_GLOBAL_OFFSET_TABLE_ = .;
+
+	. = ALIGN(4096);
 }
diff --git a/apps/test.c b/apps/test.c
index f9e40cb..592f35b 100644
--- a/apps/test.c
+++ b/apps/test.c
@@ -81,8 +81,8 @@ void serial_print(const char *data)
 		serial_put(data[i]);
 }
 
-void main()
+void start()
 {
 	serial_install();
-	serial_print("WELCOME TO USERSPACE");
+	serial_print("Follow the white rabbit.");
 }
diff --git a/src/features/elf.c b/src/features/elf.c
deleted file mode 100644
index f92f399..0000000
--- a/src/features/elf.c
+++ /dev/null
@@ -1,39 +0,0 @@
-#include <assert.h>
-#include <def.h>
-#include <elf.h>
-#include <fs.h>
-#include <mem.h>
-#include <str.h>
-
-int elf_verify(struct elf_header *h)
-{
-	return (h->ident[0] == ELF_MAG && !strncmp((char *)&h->ident[1], "ELF", 3) &&
-		h->ident[4] == ELF_32 && h->ident[5] == ELF_LITTLE && h->ident[6] == ELF_CURRENT &&
-		h->machine == ELF_386 && (h->type == ET_REL || h->type == ET_EXEC));
-}
-
-void elf_load(char *path)
-{
-	u32 *data = read_file(path);
-
-	struct elf_header *h = (struct elf_header *)data;
-	assert(elf_verify(h));
-
-	struct elf_program_header *p = (struct elf_program_header *)((u32)data + h->phoff);
-	struct elf_program_header *p_end =
-		(struct elf_program_header *)((u32)p + (h->phentsize * h->phnum));
-
-	u32 offset = (p->vaddr - p->paddr);
-	while (p < p_end) {
-		printf("\nheader: 0x%x\n", p->paddr);
-		printf("filesz: %d\n", p->filesz);
-		/* memcpy(p->paddr, (u32)data + p->offset, p->filesz); */
-		memcpy((u32 *)p->paddr, (u32 *)((u32)data + p->offset), p->filesz);
-		p++;
-	}
-
-	void (*entry)();
-	entry = (void (*)())(h->entry - offset);
-
-	entry();
-}
diff --git a/src/features/load.c b/src/features/load.c
new file mode 100644
index 0000000..37ed6ad
--- /dev/null
+++ b/src/features/load.c
@@ -0,0 +1,13 @@
+#include <def.h>
+#include <fs.h>
+#include <print.h>
+
+void bin_load(char *path)
+{
+	char *data = read_file(path);
+
+	void (*entry)();
+	*(void **)(&entry) = data + 0xfe;
+
+	entry();
+}
diff --git a/src/inc/elf.h b/src/inc/elf.h
deleted file mode 100644
index c10ba4e..0000000
--- a/src/inc/elf.h
+++ /dev/null
@@ -1,61 +0,0 @@
-// MIT License, Copyright (c) 2020 Marvin Borner
-
-#ifndef ELF_H
-#define ELF_H
-
-#include <def.h>
-
-#define ELF_MAG 0x7F // 0
-#define ELF_32 1 // 4: 32-bit Architecture
-#define ELF_LITTLE 1 // 5: Little Endian
-#define ELF_CURRENT 1 // 6: ELF Current Version
-#define ELF_386 3 // header->machine x86 machine type
-
-#define ET_NONE 0 // Unkown type
-#define ET_REL 1 // Relocatable file
-#define ET_EXEC 2 // Executable file
-
-struct elf_header {
-	u8 ident[16];
-	u16 type;
-	u16 machine;
-	u32 version;
-	u32 entry;
-	u32 phoff;
-	u32 shoff;
-	u32 flags;
-	u16 ehsize;
-	u16 phentsize;
-	u16 phnum;
-	u16 shentsize;
-	u16 shnum;
-	u16 shstrndx;
-};
-
-struct elf_section_header {
-	u32 name;
-	u32 type;
-	u32 flags;
-	u32 addr;
-	u32 offset;
-	u32 size;
-	u32 link;
-	u32 info;
-	u32 addralign;
-	u32 entsize;
-};
-
-struct elf_program_header {
-	u32 type;
-	u32 offset;
-	u32 vaddr;
-	u32 paddr;
-	u32 filesz;
-	u32 memsz;
-	u32 flags;
-	u32 align;
-};
-
-void elf_load(char *path);
-
-#endif
diff --git a/src/inc/load.h b/src/inc/load.h
new file mode 100644
index 0000000..afca249
--- /dev/null
+++ b/src/inc/load.h
@@ -0,0 +1,10 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+
+#ifndef LOAD_H
+#define LOAD_H
+
+#include <def.h>
+
+void bin_load(char *path);
+
+#endif
diff --git a/src/main.c b/src/main.c
index 283d937..68993ba 100644
--- a/src/main.c
+++ b/src/main.c
@@ -3,11 +3,11 @@
 #include "config.h"
 #include <boot.h>
 #include <def.h>
-#include <elf.h>
 #include <fs.h>
 #include <gui.h>
 #include <interrupts.h>
 #include <keyboard.h>
+#include <load.h>
 #include <print.h>
 #include <serial.h>
 #include <timer.h>
@@ -42,8 +42,7 @@ void main(struct mem_info *mem_info, struct vid_info *vid_info)
 	gui_init(FONT_PATH);
 
 	gui_term_write("Wake up, " USERNAME "...\n");
-	elf_load("/test");
-	printf("loaded");
+	bin_load("/test");
 
 	while (1) {
 	};