Embedding timestamps in FIT images results in unreproducible builds
for targets that generate a fit image, such as dra7xx_evm.

This patch uses the SOURCE_DATE_EPOCH environment variable, when set,
to use specified value for the date.

Thanks to HW42 for debugging the issue and providing the patch:

  
https://lists.alioth.debian.org/pipermail/reproducible-builds/Week-of-Mon-20160606/005722.html

For more information about reproducible builds and the
SOURCE_DATE_EPOCH specification:

  https://reproducible-builds.org/specs/source-date-epoch/
  https://reproducible-builds.org/

Signed-off-by: Vagrant Cascadian <vagr...@debian.org>
---

 tools/default_image.c | 14 +-------------
 tools/fit_image.c     |  6 ++++--
 tools/imagetool.c     | 20 ++++++++++++++++++++
 tools/imagetool.h     | 16 ++++++++++++++++
 4 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/tools/default_image.c b/tools/default_image.c
index 3ed7014..6e4ae14 100644
--- a/tools/default_image.c
+++ b/tools/default_image.c
@@ -88,7 +88,6 @@ static void image_set_header(void *ptr, struct stat *sbuf, 
int ifd,
                                struct image_tool_params *params)
 {
        uint32_t checksum;
-       char *source_date_epoch;
        time_t time;
 
        image_header_t * hdr = (image_header_t *)ptr;
@@ -98,18 +97,7 @@ static void image_set_header(void *ptr, struct stat *sbuf, 
int ifd,
                                sizeof(image_header_t)),
                        sbuf->st_size - sizeof(image_header_t));
 
-       source_date_epoch = getenv("SOURCE_DATE_EPOCH");
-       if (source_date_epoch != NULL) {
-               time = (time_t) strtol(source_date_epoch, NULL, 10);
-
-               if (gmtime(&time) == NULL) {
-                       fprintf(stderr, "%s: SOURCE_DATE_EPOCH is not valid\n",
-                               __func__);
-                       time = 0;
-               }
-       } else {
-               time = sbuf->st_mtime;
-       }
+       time = imagetool_get_source_date(params, sbuf->st_mtime);
 
        /* Build new header */
        image_set_magic(hdr, IH_MAGIC);
diff --git a/tools/fit_image.c b/tools/fit_image.c
index 0551572..23dbce4 100644
--- a/tools/fit_image.c
+++ b/tools/fit_image.c
@@ -51,8 +51,10 @@ static int fit_add_file_data(struct image_tool_params 
*params, size_t size_inc,
        }
 
        /* for first image creation, add a timestamp at offset 0 i.e., root  */
-       if (params->datafile)
-               ret = fit_set_timestamp(ptr, 0, sbuf.st_mtime);
+       if (params->datafile) {
+               time_t time = imagetool_get_source_date(params, sbuf.st_mtime);
+               ret = fit_set_timestamp(ptr, 0, time);
+       }
 
        if (!ret) {
                ret = fit_add_verification_data(params->keydir, dest_blob, ptr,
diff --git a/tools/imagetool.c b/tools/imagetool.c
index 08d191d..855a096 100644
--- a/tools/imagetool.c
+++ b/tools/imagetool.c
@@ -115,3 +115,23 @@ int imagetool_get_filesize(struct image_tool_params 
*params, const char *fname)
 
        return sbuf.st_size;
 }
+
+time_t imagetool_get_source_date(
+        struct image_tool_params *params,
+        time_t fallback)
+{
+       char *source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+
+       if (source_date_epoch == NULL)
+               return fallback;
+
+       time_t time = (time_t) strtol(source_date_epoch, NULL, 10);
+
+       if (gmtime(&time) == NULL) {
+               fprintf(stderr, "%s: SOURCE_DATE_EPOCH is not valid\n",
+                       params->cmdname);
+               time = 0;
+       }
+
+       return time;
+}
diff --git a/tools/imagetool.h b/tools/imagetool.h
index a3ed0f4..b422df2 100644
--- a/tools/imagetool.h
+++ b/tools/imagetool.h
@@ -205,6 +205,22 @@ int imagetool_save_subimage(
  */
 int imagetool_get_filesize(struct image_tool_params *params, const char 
*fname);
 
+/**
+ * imagetool_get_source_date() - Get timestamp for build output.
+ *
+ * Gets a timestamp for embedding it in a build output. If set
+ * SOURCE_DATE_EPOCH is used. Else the given fallback value is returned. Prints
+ * an error message if SOURCE_DATE_EPOCH contains an invalid value and returns
+ * 0.
+ *
+ * @params:    mkimage parameters
+ * @fallback:  timestamp to use if SOURCE_DATE_EPOCH isn't set
+ * @return timestamp based on SOURCE_DATE_EPOCH
+ */
+time_t imagetool_get_source_date(
+       struct image_tool_params *params,
+       time_t fallback);
+
 /*
  * There is a c file associated with supported image type low level code
  * for ex. default_image.c, fit_image.c
-- 
2.1.4


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