diff --git a/HACKING b/HACKING
index da0c1e84e63465c00664c64b8a5edda3083348e0..3ad87aa3626418836b8b3c1d845c17a8490fa569 100644
--- a/HACKING
+++ b/HACKING
@@ -86,3 +86,27 @@ that qemu_malloc() call with zero size is not allowed.
 Memory allocated by qemu_vmalloc or qemu_memalign must be freed with
 qemu_vfree, since breaking this will cause problems on Win32 and user
 emulators.
+
+4. String manipulation
+
+Do not use the strncpy function.  According to the man page, it does
+*not* guarantee a NULL-terminated buffer, which makes it extremely dangerous
+to use.  Instead, use functionally equivalent function:
+void pstrcpy(char *buf, int buf_size, const char *str)
+
+Don't use strcat because it can't check for buffer overflows, but:
+char *pstrcat(char *buf, int buf_size, const char *s)
+
+The same limitation exists with sprintf and vsprintf, so use snprintf and
+vsnprintf.
+
+QEMU provides other useful string functions:
+int strstart(const char *str, const char *val, const char **ptr)
+int stristart(const char *str, const char *val, const char **ptr)
+int qemu_strnlen(const char *s, int max_len)
+
+There are also replacement character processing macros for isxyz and toxyz,
+so instead of e.g. isalnum you should use qemu_isalnum.
+
+Because of the memory management rules, you must use qemu_strdup/qemu_strndup
+instead of plain strdup/strndup.