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#ifndef _INSECURE_MEMZERO_H_
#define _INSECURE_MEMZERO_H_
#include <stddef.h>
/* Pointer to memory-zeroing function. */
extern void (* volatile insecure_memzero_ptr)(volatile void *, size_t);
/**
* insecure_memzero(buf, len):
* Attempt to zero ${len} bytes at ${buf} in spite of optimizing compilers'
* best (standards-compliant) attempts to remove the buffer-zeroing. In
* particular, to avoid performing the zeroing, a compiler would need to
* use optimistic devirtualization; recognize that non-volatile objects do not
* need to be treated as volatile, even if they are accessed via volatile
* qualified pointers; and perform link-time optimization; in addition to the
* dead-code elimination which often causes buffer-zeroing to be elided.
*
* Note however that zeroing a buffer does not guarantee that the data held
* in the buffer is not stored elsewhere; in particular, there may be copies
* held in CPU registers or in anonymous allocations on the stack, even if
* every named variable is successfully sanitized. Solving the "wipe data
* from the system" problem will require a C language extension which does not
* yet exist.
*
* For more information, see:
* http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
* http://www.daemonology.net/blog/2014-09-06-zeroing-buffers-is-insufficient.html
*/
static inline void
insecure_memzero(volatile void * buf, size_t len)
{
(insecure_memzero_ptr)(buf, len);
}
#endif /* !_INSECURE_MEMZERO_H_ */
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