[PATCH 1/3] New string function explicit_bzero (from OpenBSD).

[Florian Weimer]

On 09/15/2016 03:05 PM, Zack Weinberg wrote:
> +/* As bzero, but the compiler will not delete a call to this
> +   function, even if S is dead after the call.  */
> +extern void explicit_bzero (void *__s, size_t __n) __THROW __nonnull ((1));

I would like to redirect callers to __explicit_bzero, so that shared 
objects do not accidentally pick up an implementation of explicit_bzero 
which may or may not do the right thing.

I did this in my getrandom implementation:

   <https://sourceware.org/ml/libc-alpha/2016-09/msg00203.html>

You can use __REDIRECT_NTH (meanining no exceptions) instead of __REDIRECT.

This requires exporting both __explicit_bzero and explicit_bzero.  We 
need a symbol in the implementation namespace anyway because crypt is in 
POSIX, but explicit_bzero is not.

 From the test, I would suggest to remove the fflush (stdout) calls. 
There are some whitespace GNU-style violations as well (missing space 
before paren in function call):

+struct key get_key(void);
+void use_key(struct key);
+with_clear(void)
+  k = get_key();
+  use_key(k);
+  explicit_bzero(&k, sizeof(k));
+__glibc_read_memory(const void *s, size_t len)
+      printf ("ERROR: block(SIGUSR1): %s\n", strerror (errno));
+      printf ("ERROR: sigaction(SIGUSR1): %s\n", strerror (errno));
+          printf ("ERROR: raise(SIGUSR1): %s\n", strerror (errno));
+          printf ("ERROR: unblock(SIGUSR1): %s\n", strerror (errno));
+          printf ("ERROR: unblock(SIGUSR1): %s\n", strerror(errno));

Thanks,
Florian