EFI boot header support

1 files changed, 47 insertions, 0 deletions

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;
+}