git: af8cafb2a380 - main - iovec: macros to manipulate len and base together

The branch main has been updated by brooks:

URL: https://cgit.FreeBSD.org/src/commit/?id=af8cafb2a38070907ed5c4d872599617ce9d6d48

commit af8cafb2a38070907ed5c4d872599617ce9d6d48
Author:     Brooks Davis <brooks@FreeBSD.org>
AuthorDate: 2024-06-02 18:36:55 +0000
Commit:     Brooks Davis <brooks@FreeBSD.org>
CommitDate: 2024-06-02 18:41:22 +0000

    iovec: macros to manipulate len and base together
    
    A set of convenience macros to initialize struct iovec's and increment
    the base and length together.
    
    IOVEC_INIT - sets iov_base and iov_len
    IOVEC_INIT_CSTR - takes a string and sets iov_len to strlen + 1
    IOVEC_INIT_OBJ - takes an object and sets iov_len to sizeof obj
    IOVEC_ADVANCE - increments iov_base and decrements iov_len
    
    On CheriBSD these present the opportunity to insert more precise bounds
    on some objects and hide differences in casts in hybrid kernels (where
    some, but not all pointers are capabilities and require annotation).
    Here in FreeBSD the resulting code is tidier, particularly in the
    IOVEC_ADVANCE case where the need to cast iov_base to (char *) is
    avoided.
    
    Reviewed by:    kib
    Feedback from:  des, jrtc27
    MFC after:      1 week
    Sponsored by:   AFRL, DARPA
    Differential Revision:  https://reviews.freebsd.org/D45422
---
 sys/sys/_iovec.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/sys/sys/_iovec.h b/sys/sys/_iovec.h
index 72642e5227c5..9a4eedc80b4f 100644
--- a/sys/sys/_iovec.h
+++ b/sys/sys/_iovec.h
@@ -44,4 +44,28 @@ struct iovec {
 	size_t	 iov_len;	/* Length. */
 };
 
+#ifdef _KERNEL
+#define	IOVEC_INIT(iovp, base, len) 					\
+	*(iovp) = (struct iovec){ .iov_base = (base), .iov_len = (len) }
+
+/* String with length including NUL terminator */
+#define	IOVEC_INIT_CSTR(iovp, str)	do {				\
+	void *__str = (str);						\
+	IOVEC_INIT(iovp, __str, strlen(__str) + 1);			\
+} while(0)
+
+/* Object with size from sizeof() */
+#define	IOVEC_INIT_OBJ(iovp, obj)					\
+	IOVEC_INIT(iovp, &(obj), sizeof(obj))
+
+#define	IOVEC_ADVANCE(iovp, amt)	do {				\
+	struct iovec *__iovp = (iovp);					\
+	size_t __amt = (amt);						\
+	KASSERT(__amt <= __iovp->iov_len, ("%s: amount %zu > iov_len	\
+	    %zu", __func__, __amt, __iovp->iov_len));			\
+	__iovp->iov_len -= __amt;					\
+	__iovp->iov_base = (char *)__iovp->iov_base + __amt;		\
+} while(0)
+#endif /* _KERNEL */
+
 #endif /* !_SYS__IOVEC_H_ */