From fea8b881af838b21886c5093540e1775c9b26a4f Mon Sep 17 00:00:00 2001
From: Alexander Myltsev <a.myltsev@gmail.com>
Date: Sat, 10 Feb 2024 01:39:02 +0400
Subject: [PATCH] Do not use `cat` or `type`.

---
 Makefile       |  7 ++-----
 tools/mbrpad.c | 28 ++++++++++++++++++++++------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/Makefile b/Makefile
index f0009a9..209951a 100644
--- a/Makefile
+++ b/Makefile
@@ -105,9 +105,6 @@ LDFLAGS=-m elf_i386
 user/%: user/%.o user/crt.o
 	$(LD) $(LDFLAGS) -o $@ -Ttext 0x1000 $^
 
-image.bin: mbr.bin fs.img
-	$(CAT) $^ >$@
-
 kernel.bin: $(OBJECTS)
 	$(LD) $(LDFLAGS) $(LDKERNELFLAGS) -o $@ -Ttext 0x9000 $^
 
@@ -120,9 +117,9 @@ bootmain.o: bootmain.c
 %.o: %.S
 	$(CC) $(ASMFLAGS) $^ -o $@
 
-mbr.bin: mbr.elf tools/mbrpad
+image.bin: mbr.elf tools/mbrpad fs.img
 	$(OBJCOPY) -S -O binary -j .text $< $@
-	tools/mbrpad $@
+	tools/mbrpad $@ fs.img
 
 mbr.raw: mbr.o bootmain.o
 	$(LD) -N -m elf_i386 -Ttext=0x7c00 --oformat=binary $^ -o $@
diff --git a/tools/mbrpad.c b/tools/mbrpad.c
index 4f2059d..433835a 100644
--- a/tools/mbrpad.c
+++ b/tools/mbrpad.c
@@ -3,20 +3,36 @@
 #include <stdio.h>
 #include <stdint.h>
 
+enum {
+    MBR_END = 510,
+};
+
 int main(int argc, char* argv[]) {
-    if (argc != 2) {
-        fprintf(stderr, "Usage: %s mbr.bin\n", argv[0]);
+    if (argc != 3) {
+        fprintf(stderr, "Usage: %s mbr.bin fs.img\n", argv[0]);
         return 1;
     }
     const char* filename = argv[1];
+    const char* fsimg_path = argv[2];
     int fd = open(filename, O_RDWR);
     off_t length = lseek(fd, 0, SEEK_END);
-    if (length > 510) {
-        fprintf(stderr, "file %s is larger than 510 bytes (size: %llu)\n",
-                filename, (unsigned long long)length);
+    if (length > MBR_END) {
+        fprintf(stderr, "file %s is larger than %d bytes (size: %llu)\n",
+                filename, MBR_END, (unsigned long long)length);
         return 1;
     }
-    lseek(fd, 510, SEEK_SET);
+    lseek(fd, MBR_END, SEEK_SET);
     write(fd, "\x55\xaa", 2);
+
+    int fsimg = open(fsimg_path, O_RDONLY);
+    if (fsimg < 0) {
+        perror(fsimg_path);
+        return 1;
+    }
+    char buf[1024];
+    ssize_t bytes;
+    while ((bytes = read(fsimg, buf, sizeof(buf))) > 0) {
+        write(fd, buf, bytes);
+    }
     return 0;
 }