.TH MEMORY 2
.SH NAME
-memccpy, memchr, memcmp, memcpy, memmove, memset \- memory operations
+memccpy, memchr, memcmp, memcpy, memmove, memset, tsmemcmp \- memory operations
.SH SYNOPSIS
.B #include <u.h>
.br
.PP
.B
void* memset(void *s, int c, ulong n)
+.PP
+.B #include <libsec.h>
+.PP
+.B
+int tsmemcmp(void *s1, void *s2, ulong n)
.SH DESCRIPTION
These functions operate efficiently on memory areas
(arrays of bytes bounded by a count, not terminated by a zero byte).
.IR c .
It returns
.IR s .
+.PP
+.I Tsmemcmp
+is a variant of
+.I memcmp
+that is safe against timing attacks.
+It does not stop when it sees a difference, this way it's runtime is function of
+.I n
+and not something that can lead clues to attackers.
.SH SOURCE
All these routines have portable C implementations in
.BR /sys/src/libc/port .
Most also have machine-dependent assembly language implementations in
.BR /sys/src/libc/$objtype .
+.I Tsmemcmp
+is found on
+.BR /sys/src/libsec/port/tsmemcmp.c .
.SH SEE ALSO
.IR strcat (2)
.SH BUGS
and
.I memmove
are handed a negative count, they abort.
+.PP
+.I Memcmp
+should not be used to compare sensitive data as it's vulnerable to timing attacks. Instead,
+.I tsmemcmp
+should be used.