In gcc/toplev.c, there's the comment:
/* A local time stamp derived from the time of compilation. It will be
zero if the system cannot provide a time. It will be -1u, if the
user has specified a particular random seed. */
unsigned local_tick;
This is affirmed by init_local_tick()'s comment:
/* Initialize local_tick with the time of day, or -1 if
flag_random_seed is set. */
static void init_local_tick (void)
And indeed we see it assigned -1 when flag_random_seed != NULL:
else
local_tick = -1;
So far so good. However, in the case where flag_random_seed == NULL,
local_tick is assigned like this:
struct timeval tv;
gettimeofday (&tv, NULL);
local_tick = (unsigned) tv.tv_sec * 1000 + tv.tv_usec / 1000;
local_tick is currently of type "unsigned int". Somewhat often, that
expression calculates to be 0xffffffff, which means local_tick winds up
being -1 even when flag_random_seed == NULL.
Interestingly enough, Jakub already fixed one such overflow with that
assignment with 3db31fd1cc7 ("toplev.c (init_local_tick): Avoid signed
integer multiplication overflow."), but this patch missed the integer
size issue.
This is a problem for plugins that follow the documentation comments in
order to determine whether -frandom-seed is being used. To work around
this bug, these plugins must either call get_random_seed(noinit=true) in
their plugin init functions and check there whether the return value is
zero, or more laboriously reparse common_deferred_options or
save_decoded_options. If they use a local_tick==-1 check, once in a blue
moon, it'll be wrong.
Actually, one such user of this isn't a plugin and is actually in tree:
coverage.cc, which unlink()s a file that it shouldn't from time to time:
if (!flag_branch_probabilities && flag_test_coverage
&& (!local_tick || local_tick == (unsigned)-1))
/* Only remove the da file, if we're emitting coverage code and
cannot uniquely stamp it. If we can stamp it, libgcov will DTRT. */
unlink (da_file_name);
This patch fixes the issue by just making local_tick 64 bits, which
should also allow that timestamp to be a bit more unique as well. This
way there's no possibility of overflowing to -1. It then changes the
comparisons to use the properly typed HOST_WIDE_INT_M1U macro.
Cc: PaX Team <pagee...@freemail.hu>
Cc: Brad Spengler <spen...@grsecurity.net>
Cc: Andrew Pinski <pins...@gcc.gnu.org>
Cc: Jakub Jelinek <ja...@gcc.gnu.org>
Closes: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105171
Fixes: c07e5477521 ("tree.h (default_flag_random_seed): Remove.")
Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com>
---
gcc/coverage.cc | 4 ++--
gcc/toplev.cc | 10 +++++-----
gcc/toplev.h | 2 +-
3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/gcc/coverage.cc b/gcc/coverage.cc
index 8ece5db680e..aa482152b3b 100644
--- a/gcc/coverage.cc
+++ b/gcc/coverage.cc
@@ -1310,7 +1310,7 @@ coverage_init (const char *filename)
memcpy (da_file_name + prefix_len, filename, len);
strcpy (da_file_name + prefix_len + len, GCOV_DATA_SUFFIX);
- bbg_file_stamp = local_tick;
+ bbg_file_stamp = (unsigned) local_tick;
if (flag_auto_profile)
read_autofdo_file ();
else if (flag_branch_probabilities)
@@ -1360,7 +1360,7 @@ coverage_finish (void)
unlink (bbg_file_name);
if (!flag_branch_probabilities && flag_test_coverage
- && (!local_tick || local_tick == (unsigned)-1))
+ && (!local_tick || local_tick == HOST_WIDE_INT_M1U))
/* Only remove the da file, if we're emitting coverage code and
cannot uniquely stamp it. If we can stamp it, libgcov will DTRT. */
unlink (da_file_name);
diff --git a/gcc/toplev.cc b/gcc/toplev.cc
index 2d432fb2d84..7c6badeb052 100644
--- a/gcc/toplev.cc
+++ b/gcc/toplev.cc
@@ -135,9 +135,9 @@ const char * current_function_func_begin_label;
static const char *flag_random_seed;
/* A local time stamp derived from the time of compilation. It will be
- zero if the system cannot provide a time. It will be -1u, if the
+ zero if the system cannot provide a time. It will be -1, if the
user has specified a particular random seed. */
-unsigned local_tick;
+unsigned HOST_WIDE_INT local_tick;
/* Random number for this compilation */
HOST_WIDE_INT random_seed;
@@ -248,19 +248,19 @@ init_local_tick (void)
struct timeval tv;
gettimeofday (&tv, NULL);
- local_tick = (unsigned) tv.tv_sec * 1000 + tv.tv_usec / 1000;
+ local_tick = (unsigned HOST_WIDE_INT) tv.tv_sec * 1000 + tv.tv_usec /
1000;
}
#else
{
time_t now = time (NULL);
if (now != (time_t)-1)
- local_tick = (unsigned) now;
+ local_tick = (unsigned HOST_WIDE_INT) now;
}
#endif
}
else
- local_tick = -1;
+ local_tick = HOST_WIDE_INT_M1U;
}
/* Obtain the random_seed. Unless NOINIT, initialize it if
diff --git a/gcc/toplev.h b/gcc/toplev.h
index a82ef8b8fd3..4468396b725 100644
--- a/gcc/toplev.h
+++ b/gcc/toplev.h
@@ -74,7 +74,7 @@ extern void dump_profile_report (void);
extern void target_reinit (void);
/* A unique local time stamp, might be zero if none is available. */
-extern unsigned local_tick;
+extern unsigned HOST_WIDE_INT local_tick;
/* See toplev.cc. */
extern int flag_rerun_cse_after_global_opts;
--
2.35.1
