bootctl: add comments emphasizing that certain functions do not touch the file read pointer

src/bootctl/bootctl-install.c

@@ -490,6 +490,8 @@ static int version_check(int fd_from, const char *from, int fd_to, const char *t
         assert(fd_to >= 0);
         assert(to);
 
+        /* Does not reposition file offset */
+
         r = get_file_version(fd_from, &a);
         if (r == -ESRCH)
                 return log_notice_errno(r, "Source file \"%s\" does not carry version information!", from);

src/bootctl/bootctl-util.c

@@ -75,6 +75,8 @@ int get_file_version(int fd, char **ret) {
         assert(fd >= 0);
         assert(ret);
 
+        /* Does not reposition file offset (as it uses mmap()) */
+
         if (fstat(fd, &st) < 0)
                 return log_error_errno(errno, "Failed to stat EFI binary: %m");
 

src/shared/pe-binary.c

@@ -12,6 +12,8 @@
 #include "string-table.h"
 #include "string-util.h"
 
+/* Note: none of these function change the file position of the provided fd, as they use pread() */
+
 bool pe_header_is_64bit(const PeHeader *h) {
         assert(h);