dist/tools/riotboot_gen_hdr/genhdr: add update command

Sometimes we want to roll-back to a previous firmware version.
To do so we need a higher riotbot version numbers still.

Add an update command to the riotboot_gen_hdr tool so that an existing
firmware image can be re-rolled out with a new version number.

dist/tools/riotboot_gen_hdr/common.c

@@ -17,7 +17,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-int to_file(const char *filename, void *buf, size_t len)
+int to_file(const char *filename, const void *buf, size_t len)
 {
     int fd;
 
@@ -37,3 +37,24 @@ int to_file(const char *filename, void *buf, size_t len)
         return fd;
     }
 }
+
+int from_file(const char *filename, void *buf, size_t len)
+{
+    int fd;
+
+    if (strcmp("-", filename)) {
+        fd = open(filename, O_RDONLY, 0);
+    }
+    else {
+        fd = STDIN_FILENO;
+    }
+
+    if (fd > 0) {
+        ssize_t res = read(fd, buf, len);
+        close(fd);
+        return res;
+    }
+    else {
+        return fd;
+    }
+}

dist/tools/riotboot_gen_hdr/common.h

@@ -17,12 +17,23 @@
 /**
  * @brief  Write len bytes of a given buffer into a file
  *
- * @param[out] filename    name of the file to be written
+ * @param[in]  filename    name of the file to be written
  * @param[in]  buf         a pointer to the buffer which needs to be written
  * @param[in]  len         the number of bytes from buf to be written
  *
  */
-int to_file(const char *filename, void *buf, size_t len);
+int to_file(const char *filename, const void *buf, size_t len);
+
+/**
+ * @brief  Read len bytes from a given file into a buffer
+ *
+ * @param[in]  filename  name of the file to be read
+ * @param[out] buf       a pointer to the buffer to store the content
+ * @param[out] len       the number of bytes to be read
+ *
+ * @return  Number of bytes read, or negative error
+ */
+int from_file(const char *filename, const void *buf, size_t len);
 
 #ifdef __cplusplus
 } /* end extern "C" */

dist/tools/riotboot_gen_hdr/genhdr.c

@@ -112,3 +112,51 @@ int genhdr(int argc, char *argv[])
 
     return 0;
 }
+
+int updatehdr(int argc, char *argv[])
+{
+    if (argc < 3) {
+        fprintf(stderr, "usage: genhdr update <file> <new_version>\n");
+        return -1;
+    }
+    const char *file = argv[1];
+
+    riotboot_hdr_t hdr = { 0 };
+    int res = from_file(file, &hdr, sizeof(hdr));
+    if (res < (int)sizeof(hdr)) {
+        fprintf(stderr, "Can't read header from %s\n", file);
+        return -EIO;
+    }
+
+    if (hdr.magic_number != RIOTBOOT_MAGIC) {
+        fprintf(stderr, "Invalid magic: %x\n", hdr.magic_number);
+        return -EIO;
+    }
+
+    hdr.version = atoi(argv[2]);
+    hdr.chksum = riotboot_hdr_checksum(&hdr);
+    to_file(file, &hdr, sizeof(hdr));
+
+    return 0;
+}
+
+int readhdr(const char *file)
+{
+    riotboot_hdr_t hdr = { 0 };
+    int res = from_file(file, &hdr, sizeof(hdr));
+    if (res < (int)sizeof(hdr)) {
+        fprintf(stderr, "Can't read header from %s\n", file);
+        return -EIO;
+    }
+
+    if (hdr.magic_number != RIOTBOOT_MAGIC) {
+        fprintf(stderr, "Invalid magic: %x\n", hdr.magic_number);
+        return -EIO;
+    }
+
+    printf("version: %u\n", hdr.version);
+    printf("address: 0x%x\n", hdr.start_addr);
+    printf("checksum: %svalid\n", riotboot_hdr_validate(&hdr) ? "in" : "");
+
+    return 0;
+}

dist/tools/riotboot_gen_hdr/main.c

@@ -18,10 +18,14 @@
 #include <string.h>
 
 int genhdr(int argc, char *argv[]);
+int updatehdr(int argc, char *argv[]);
+int readhdr(const char *file);
 
 int main(int argc, char *argv[])
 {
-    char *usage = "genhdr generate [args]";
+    char *usage = "genhdr generate [args]\n\t"
+                  "genhdr update [file] [new_version]\n\t"
+                  "genhdr show [file]";
 
     if (argc < 2) {
         goto usage;
@@ -29,8 +33,14 @@ int main(int argc, char *argv[])
     else if (!strcmp(argv[1], "generate")) {
         return genhdr(argc - 1, &argv[1]);
     }
+    else if (!strcmp(argv[1], "update")) {
+        return updatehdr(argc - 1, &argv[1]);
+    }
+    else if (!strcmp(argv[1], "show")) {
+        return readhdr(argv[2]);
+    }
 
 usage:
-    fprintf(stderr, "usage: %s\n", usage);
+    fprintf(stderr, "usage:\t%s\n", usage);
     return 1;
 }