EFI boot header support

4 files changed, 103 insertions, 4 deletions

diff --git a/Makefile b/Makefile
index 8ea760b..ad38c9a 100644
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,7 @@ VERSION = 0.1.0-alpha
 
 CC = clang
 LD = ld.lld
+NM = llvm-nm
 OBJCOPY = llvm-objcopy
 
 COMPILER = $(shell $(CC) --version | head -n 1)
@@ -99,20 +100,27 @@ KERNEL_OBJS = $(KERNEL_SRCS:.c=.o)
 KERNEL_OBJS := $(KERNEL_OBJS:.S=.o)
 KERNEL_BIN := $(KERNEL_TARGET)/kernel.bin
 KERNEL_ELF := $(KERNEL_TARGET)/kernel.elf
+KERNEL_IMAGE := $(KERNEL_TARGET)/Image
+
+KASSEMBLE_BIN := misc/kassemble
+KASSEMBLE_SRC := misc/kassemble.c
 
 GENERATED = \
 	$(KERNEL_OBJS) \
 	$(KERNEL_ELF) \
 	$(KERNEL_BIN) \
+	$(KERNEL_IMAGE) \
 	$(foreach m,$(MODULES),$(m)/$(m).elf) \
 	$(foreach m,$(MODULES),$(m)/$(m).ko) \
-	$(foreach m,$(MODULES),$($(m)_OBJS))
+	$(foreach m,$(MODULES),$($(m)_OBJS)) \
+	$(KASSEMBLE_BIN)
 
-.PHONY: all kernel clean modules $(MODULES)
+.PHONY: all kernel kassemble clean modules $(MODULES)
 $(V).SILENT:
-all: kernel modules
-kernel: $(KERNEL_BIN)
+all: kassemble kernel modules 
+kernel: $(KERNEL_IMAGE)
 modules: $(MODULES)
+kassemble: $(KASSEMBLE_BIN)
 $(MODULES): $(MODULE_OBJECTS)
 
 %.o: %.c
@@ -122,6 +130,10 @@ $(MODULES): $(MODULE_OBJECTS)
 	@echo " AS $<"
 	$(CC) $(KERNEL_CFLAGS) -c $< -o $@
 
+$(KASSEMBLE_BIN): $(KASSEMBLE_SRC)
+	@echo " HOSTCC $<"
+	$(CC) -O2 $< -o $@
+
 $(KERNEL_ELF): $(KERNEL_OBJS) $(KERNEL_LD) | $(KERNEL_OUTDIR)/
 	@echo " LD $@"
 	$(LD) $(KERNEL_LD_FLAG) $(KERNEL_OBJS) -o $@
@@ -130,6 +142,10 @@ $(KERNEL_BIN): $(KERNEL_ELF) | $(KERNEL_OUTDIR)/
 	@echo " OBJCOPY $@"
 	$(OBJCOPY) $(KERNEL_OBJCOPY_FLAG) $(KERNEL_ELF) $(KERNEL_BIN)
 
+$(KERNEL_IMAGE): $(KERNEL_BIN) | $(KERNEL_OUTDIR)/
+	@echo " KASSEMBLE $@"
+	$(KASSEMBLE_BIN) $< $@ $$($(NM) $(KERNEL_ELF) | awk '/__image_size/{print $$1}')
+
 clean:
 	@echo " CLEAN $(GENERATED)"
 	$(RM) $(GENERATED)
diff --git a/kernel/riscv/header.S b/kernel/riscv/header.S
new file mode 100644
index 0000000..cca2594
--- /dev/null
+++ b/kernel/riscv/header.S
@@ -0,0 +1,23 @@
+.section .header, "a", @progbits
+.extern _start
+#define CODE0 0x4d, 0x5a, 0, 0
+#define FLAGS 0
+#define TEXT_OFFSET 0
+#define HEADER_VERSION 0x00000002
+#define RES1 0
+#define RES2 0
+#define RES3 0
+#define MAGIC 0x5643534952
+#define MAGIC2 0x05435352
+header:
+    .byte CODE0
+    j _start
+    .quad TEXT_OFFSET
+    .quad 0 # image_size
+    .quad FLAGS
+    .int HEADER_VERSION
+    .int RES1
+    .quad RES2
+    .quad MAGIC
+    .int MAGIC2
+    .int RES3
diff --git a/kernel/riscv/linker.ld b/kernel/riscv/linker.ld
index ec51176..6689dce 100644
--- a/kernel/riscv/linker.ld
+++ b/kernel/riscv/linker.ld
@@ -10,6 +10,11 @@ MEMORY
 
 SECTIONS
 {
+    .header : {
+        KEEP(*(.header))
+        *(.header)
+    } > ROM
+
     .text : {
         KEEP(*(.text._start))
         KEEP(*(.text.start))
@@ -60,6 +65,11 @@ SECTIONS
         __ringbuf_end = .;
     } > LOGRAM
 
+    .image_end (NOLOAD) : {
+        . = ALIGN(4);
+        __image_end = .;
+    } > ROM
+
     /DISCARD/ : {
         *(.eh_frame)
         *(.eh_frame.*)
@@ -71,4 +81,7 @@ SECTIONS
         *(.llvm_*)
         *(.rela.*)
     }
+
+    __image_start = ORIGIN(ROM);
+    __image_size = __image_end - __image_start;
 }
diff --git a/misc/kassemble.c b/misc/kassemble.c
new file mode 100644
index 0000000..a818cc5
--- /dev/null
+++ b/misc/kassemble.c
@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <errno.h>
+
+int main(int argc, char **argv) {
+    if (argc != 4) {
+        fprintf(stderr, "usage: %s <in> <out> <image_size>\n", argv[0]);
+        return 1;
+    }
+
+    const char *in_path  = argv[1];
+    const char *out_path = argv[2];
+    char *end;
+    errno = 0;
+    unsigned long long size = strtoull(argv[3], &end, 16);
+    if (errno || *end != '\0') {
+        fprintf(stderr, "bad size: %s, invalid chars: %s\n", argv[3], end);
+        return 1;
+    }
+
+    FILE *in = fopen(in_path, "rb");
+    if (!in) { perror("fopen in"); return 1; }
+
+    FILE *out = fopen(out_path, "wb");
+    if (!out) { perror("fopen out"); fclose(in); return 1; }
+
+    /* Copy in -> out */
+    unsigned char buf[65536];
+    size_t n;
+    while ((n = fread(buf, 1, sizeof buf, in)) > 0) {
+        if (fwrite(buf, 1, n, out) != n) { perror("fwrite"); return 1; }
+    }
+    if (ferror(in)) { perror("fread"); return 1; }
+
+    /* Write size as u64 little-endian at offset 16 */
+    unsigned char le[8];
+    for (int i = 0; i < 8; i++)
+        le[i] = (unsigned char)(size >> (8 * i));
+
+    if (fseek(out, 16, SEEK_SET) != 0) { perror("fseek"); return 1; }
+    if (fwrite(le, 1, 8, out) != 8)    { perror("fwrite size"); return 1; }
+
+    fclose(in);
+    if (fclose(out) != 0) { perror("fclose out"); return 1; }
+    return 0;
+}