string: add stracpy and stracpy_pad mechanisms

Several uses of strlcpy and strscpy have had defects because the last
argument of each function is misused or typoed.

Add macro mechanisms to avoid this defect.

stracpy (copy a string to a string array) must have a string array as the
first argument (dest) and uses sizeof(dest) as the count of bytes to copy.

These mechanisms verify that the dest argument is an array of char or
other compatible types like u8 or s8 or equivalent.

A BUILD_BUG is emitted when the type of dest is not compatible.

Signed-off-by: Joe Perches <>
Reviewed-by: Kees Cook <>
Cc: Jann Horn <>
Cc: Jonathan Corbet <>
Cc: Nitin Gote <>
Cc: Rasmus Villemoes <>
Cc: Stephen Kitt <>
Signed-off-by: Andrew Morton <>
1 file changed