reproducible: fix DATE/TIME macros in toolchain-wrapper

The use of the __DATE__ and __TIME__ macros are one of the most common
sources of non-reproducible binaries. In order to fix that, gcc 7 supports
the SOURCE_DATE_EPOCH variable:

https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=e3e8c48c4a494d9da741c1c8ea6c4c0b7c4ff934

This patch take advantage of toolchain-wrapper to provide support of
SOURCE_DATE_EPOCH to older gcc versions.

Function get_source_date_epoch() come directly from gcc git.

This work was sponsored by `BA Robotic Systems'.

[Peter: use sizeof for character array sizes, make function static,
	extend commit message, add upstream gcc commit]
Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

diff --git a/toolchain/toolchain-wrapper.c b/toolchain/toolchain-wrapper.c
index 100aa181c6805d3161d321c1ae2a937d522b9530..eb4ee8de4ac11d771599c6b614e10fb6ec5ac139 100644 (file)
--- a/toolchain/toolchain-wrapper.c
+++ b/toolchain/toolchain-wrapper.c
@@ -22,12 +22,15 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <errno.h>
+#include <time.h>
 
 #ifdef BR_CCACHE
 static char ccache_path[PATH_MAX];
 #endif
 static char path[PATH_MAX];
 static char sysroot[PATH_MAX];
+static char source_time[sizeof("-D__TIME__=\"HH:MM:SS\"")];
+static char source_date[sizeof("-D__DATE__=\"MMM DD YYYY\"")];
 
 /**
  * GCC errors out with certain combinations of arguments (examples are
@@ -39,8 +42,11 @@ static char sysroot[PATH_MAX];
  *     -mfloat-abi=
  *     -march=
  *     -mcpu=
+ *     -D__TIME__=
+ *     -D__DATE__=
+ *     -Wno-builtin-macro-redefined
  */
-#define EXCLUSIVE_ARGS 3
+#define EXCLUSIVE_ARGS 6
 
 static char *predef_args[] = {
 #ifdef BR_CCACHE
@@ -157,6 +163,47 @@ static void check_unsafe_path(const char *arg,
        }
 }
 
+/* Read SOURCE_DATE_EPOCH from environment to have a deterministic
+ * timestamp to replace embedded current dates to get reproducible
+ * results.  Returns -1 if SOURCE_DATE_EPOCH is not defined.
+ */
+static time_t get_source_date_epoch()
+{
+       char *source_date_epoch;
+       long long epoch;
+       char *endptr;
+
+       source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+       if (!source_date_epoch)
+               return (time_t) -1;
+
+       errno = 0;
+       epoch = strtoll(source_date_epoch, &endptr, 10);
+       if ((errno == ERANGE && (epoch == LLONG_MAX || epoch == LLONG_MIN))
+                       || (errno != 0 && epoch == 0)) {
+               fprintf(stderr, "environment variable $SOURCE_DATE_EPOCH: "
+                               "strtoll: %s\n", strerror(errno));
+               exit(2);
+       }
+       if (endptr == source_date_epoch) {
+               fprintf(stderr, "environment variable $SOURCE_DATE_EPOCH: "
+                               "no digits were found: %s\n", endptr);
+               exit(2);
+       }
+       if (*endptr != '\0') {
+               fprintf(stderr, "environment variable $SOURCE_DATE_EPOCH: "
+                               "trailing garbage: %s\n", endptr);
+               exit(2);
+       }
+       if (epoch < 0) {
+               fprintf(stderr, "environment variable $SOURCE_DATE_EPOCH: "
+                               "value must be nonnegative: %lld \n", epoch);
+               exit(2);
+       }
+
+       return (time_t) epoch;
+}
+
 int main(int argc, char **argv)
 {
        char **args, **cur, **exec_args;
@@ -167,6 +214,7 @@ int main(int argc, char **argv)
        char *paranoid_wrapper;
        int paranoid;
        int ret, i, count = 0, debug;
+       time_t source_date_epoch;
 
        /* Calculate the relative paths */
        basename = strrchr(progpath, '/');
@@ -272,6 +320,28 @@ int main(int argc, char **argv)
        }
 #endif /* ARCH || CPU */
 
+       source_date_epoch = get_source_date_epoch();
+       if (source_date_epoch != -1) {
+               struct tm *tm = localtime(&source_date_epoch);
+               if (!tm) {
+                       perror("__FILE__: localtime");
+                       return 3;
+               }
+               ret = strftime(source_time, sizeof(source_time), "-D__TIME__=\"%T\"", tm);
+               if (!ret) {
+                       perror("__FILE__: overflow");
+                       return 3;
+               }
+               *cur++ = source_time;
+               ret = strftime(source_date, sizeof(source_date), "-D__DATE__=\"%b %e %Y\"", tm);
+               if (!ret) {
+                       perror("__FILE__: overflow");
+                       return 3;
+               }
+               *cur++ = source_date;
+               *cur++ = "-Wno-builtin-macro-redefined";
+       }
+
        paranoid_wrapper = getenv("BR_COMPILER_PARANOID_UNSAFE_PATH");
        if (paranoid_wrapper && strlen(paranoid_wrapper) > 0)
                paranoid = 1;