Date: Wed, 14 Jan 2026 17:10:49 +0000 From: John Baldwin <jhb@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 2a5c5b8f7cdd - main - swab: Correctly treat the data as misaligned Message-ID: <6967ce19.33005.39ad7fa@gitrepo.freebsd.org>
index | next in thread | raw e-mail
The branch main has been updated by jhb: URL: https://cgit.FreeBSD.org/src/commit/?id=2a5c5b8f7cddf14537707895fceb454cabc1b3bd commit 2a5c5b8f7cddf14537707895fceb454cabc1b3bd Author: John Baldwin <jhb@FreeBSD.org> AuthorDate: 2026-01-14 17:10:33 +0000 Commit: John Baldwin <jhb@FreeBSD.org> CommitDate: 2026-01-14 17:10:33 +0000 swab: Correctly treat the data as misaligned The __aligned attribute in the previous version applied to the location of the pointers, not the data the pointers pointed to. While this could be fixed by applying the attribute to a local typedef of uint16_t, just using memcpy() for the unaligned access is simpler and ISO C. This fixes the build on CHERI architectures which do not support misaligned pointers and were thus failing with: lib/libc/string/swab.c:12:18: error: alignment (1) of 'const uint16_t *' (aka 'const unsigned short *') is less than the required capability alignment (16) [-Werror,-Wcheri-capability-misuse] 12 | const uint16_t *f __aligned(1) = from; | Co-authored by: Jessica Clarke <jrtc27@FreeBSD.org> Fixes: 02ebbc781f08 ("swab: Fix implementation to support overlapping copies") Sponsored by: AFRL, DARPA Reviewed by: markj Differential Revision: https://reviews.freebsd.org/D54399 --- lib/libc/string/swab.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/lib/libc/string/swab.c b/lib/libc/string/swab.c index ed4436a49810..4f4fb26379c6 100644 --- a/lib/libc/string/swab.c +++ b/lib/libc/string/swab.c @@ -3,14 +3,16 @@ * Copyright (c) 2024 rilysh <nightquick@proton.me> */ +#include <string.h> #include <unistd.h> #include <sys/endian.h> void swab(const void * __restrict from, void * __restrict to, ssize_t len) { - const uint16_t *f __aligned(1) = from; - uint16_t *t __aligned(1) = to; + const char *f = from; + char *t = to; + uint16_t tmp; /* * POSIX says overlapping copy behavior is undefined, however many @@ -19,7 +21,12 @@ swab(const void * __restrict from, void * __restrict to, ssize_t len) * and swapping them before writing them back accomplishes this. */ while (len > 1) { - *t++ = bswap16(*f++); + memcpy(&tmp, f, 2); + tmp = bswap16(tmp); + memcpy(t, &tmp, 2); + + f += 2; + t += 2; len -= 2; } }home | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?6967ce19.33005.39ad7fa>