Date: Thu, 09 Apr 2026 02:37:35 +0000 From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 9a8d333368ba - main - libc: fix memfd_create's HUGETLB handling Message-ID: <69d710ef.41b26.b5557b0@gitrepo.freebsd.org>
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The branch main has been updated by kevans: URL: https://cgit.FreeBSD.org/src/commit/?id=9a8d333368baef356f0a611b47ec592568dd14f9 commit 9a8d333368baef356f0a611b47ec592568dd14f9 Author: Kyle Evans <kevans@FreeBSD.org> AuthorDate: 2026-04-09 02:37:00 +0000 Commit: Kyle Evans <kevans@FreeBSD.org> CommitDate: 2026-04-09 02:37:11 +0000 libc: fix memfd_create's HUGETLB handling The 'simplification' commit referenced below actually broke one aspect of MFD_HUGETLB: the caller isn't supposed to be required to specify a size. MFD_HUGETLB by itself without a shift mask just requests a large page, so we revert that part of memfd_create() back. While we're here, fix up the related parts of the manpages a little bit, since MFD_HUGETLB is actually supported. The manpage claims that we would return ENOSYS if forced mappings weren't supported, but this was actually not true. However, that seems like a very important distinction to make between ENOSYS and EOPNOTSUPP, so fix the implementation to match the docs. Fixes: 8b8cf4ece660f ("memfd_create: simplify HUGETLB support [...]") Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D56114 --- lib/libc/gen/memfd_create.c | 23 +++++++++++++------ lib/libsys/shm_open.2 | 31 ++++++++++++++++++++++---- tests/sys/posixshm/memfd_test.c | 35 +++++++++++++++++++++++++++++ tests/sys/posixshm/posixshm.h | 45 ++++++++++++++++++++++++++++++++++++++ tests/sys/posixshm/posixshm_test.c | 38 +++++++++++--------------------- 5 files changed, 136 insertions(+), 36 deletions(-) diff --git a/lib/libc/gen/memfd_create.c b/lib/libc/gen/memfd_create.c index 78131f46d7b1..8e6c93be4337 100644 --- a/lib/libc/gen/memfd_create.c +++ b/lib/libc/gen/memfd_create.c @@ -95,16 +95,25 @@ memfd_create(const char *name, unsigned int flags) npgs = getpagesizes(pgs, nitems(pgs)); if (npgs == -1) goto clean; - pgsize = (size_t)1 << ((flags & MFD_HUGE_MASK) >> MFD_HUGE_SHIFT); - for (pgidx = 0; pgidx < npgs; pgidx++) { - if (pgsize == pgs[pgidx]) - break; - } - if (pgidx == npgs) { - errno = EOPNOTSUPP; + else if (npgs == 1) { + errno = ENOSYS; goto clean; } + if ((flags & MFD_HUGE_MASK) == 0) { + pgidx = 1; + } else { + pgsize = 1UL << ((flags & MFD_HUGE_MASK) >> MFD_HUGE_SHIFT); + for (pgidx = 1; pgidx < npgs; pgidx++) { + if (pgsize == pgs[pgidx]) + break; + } + if (pgidx == npgs) { + errno = EOPNOTSUPP; + goto clean; + } + } + memset(&slc, 0, sizeof(slc)); slc.psind = pgidx; slc.alloc_policy = SHM_LARGEPAGE_ALLOC_DEFAULT; diff --git a/lib/libsys/shm_open.2 b/lib/libsys/shm_open.2 index c3196d966e6b..58597a341b9e 100644 --- a/lib/libsys/shm_open.2 +++ b/lib/libsys/shm_open.2 @@ -26,7 +26,7 @@ .\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd August 4, 2025 +.Dd March 26, 2025 .Dt SHM_OPEN 2 .Os .Sh NAME @@ -343,7 +343,25 @@ Allow adding seals to the resulting file descriptor using the .Xr fcntl 2 command. .It Dv MFD_HUGETLB -This flag is currently unsupported. +Create a memfd backed by a +.Dq largepage +object. +One of the +.Dv MFD_HUGE_* +flags defined in +.In sys/mman.h +may be included to specify a fixed size. +If a specific size is not requested, the smallest supported large page size is +selected. +.Pp +The behavior documented above for the +.Fn shm_create_largepage +.Fa psind +argument also applies to largepage objects created by +.Fn memfd_create , +and the +.Dv SHM_LARGEPAGE_ALLOC_DEFAULT +policy will always be used. .El .Sh RETURN VALUES If successful, @@ -458,17 +476,22 @@ argument was too long. .Pp An invalid or unsupported flag was included in .Fa flags . +.It Bq Er EINVAL +A hugetlb mapping was requested, but +.Dv MFD_HUGETLB +was not specified in +.Fa flags . .It Bq Er EMFILE The process has already reached its limit for open file descriptors. .It Bq Er ENFILE The system file table is full. .It Bq Er ENOSYS -In -.Fa memfd_create , .Dv MFD_HUGETLB was specified in .Fa flags , and this system does not support forced hugetlb mappings. +.It Bq Er EOPNOTSUPP +This system does not support the requested hugetlb page size. .El .Pp .Fn shm_open diff --git a/tests/sys/posixshm/memfd_test.c b/tests/sys/posixshm/memfd_test.c index 5cae184206b1..387eca4cafe9 100644 --- a/tests/sys/posixshm/memfd_test.c +++ b/tests/sys/posixshm/memfd_test.c @@ -34,6 +34,8 @@ #include <errno.h> #include <unistd.h> +#include "posixshm.h" + ATF_TC_WITHOUT_HEAD(basic); ATF_TC_BODY(basic, tc) { @@ -277,6 +279,38 @@ ATF_TC_BODY(immutable_seals, tc) close(fd); } +ATF_TC_WITHOUT_HEAD(hugetlb); +ATF_TC_BODY(hugetlb, tc) +{ + size_t ps[MAXPAGESIZES], pgsize; + int fd, pscnt; + + pscnt = pagesizes(ps, false); +#define MFD_HUGE_SUPPORTED(sz) (sz <= (1 << 24)) +#define MFD_HUGE_FLAGS(sz) (((ffsl(sz) - 1U) << MFD_HUGE_SHIFT) & MFD_HUGE_MASK) + for (int psidx = 1; psidx < pscnt; psidx++) { + pgsize = ps[psidx]; + + if (!MFD_HUGE_SUPPORTED(pgsize)) + continue; + + ATF_REQUIRE_MSG((fd = memfd_create("...", + MFD_HUGETLB | MFD_HUGE_FLAGS(pgsize))) != -1, + "Creating a %zu-size hugetlb memfd", pgsize); + } + + fd = memfd_create("...", MFD_HUGETLB); + if (pscnt == 1) { + ATF_REQUIRE_MSG(fd == -1, + "Creating an unspecified hugetlb memfd without large page support"); + ATF_REQUIRE(errno == ENOSYS); + } else { + ATF_REQUIRE_MSG(fd != -1, + "Creating an unspecified hugetlb memfd with large page support"); + close(fd); + } +} + ATF_TP_ADD_TCS(tp) { @@ -289,5 +323,6 @@ ATF_TP_ADD_TCS(tp) ATF_TP_ADD_TC(tp, get_seals); ATF_TP_ADD_TC(tp, dup_seals); ATF_TP_ADD_TC(tp, immutable_seals); + ATF_TP_ADD_TC(tp, hugetlb); return (atf_no_error()); } diff --git a/tests/sys/posixshm/posixshm.h b/tests/sys/posixshm/posixshm.h new file mode 100644 index 000000000000..84c73e0d10df --- /dev/null +++ b/tests/sys/posixshm/posixshm.h @@ -0,0 +1,45 @@ +/*- + * + * Copyright (c) 2020 Klara, Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <sys/param.h> +#include <sys/mman.h> + +#include <stdbool.h> + +static int +pagesizes(size_t ps[MAXPAGESIZES], bool required) +{ + int pscnt; + + pscnt = getpagesizes(ps, MAXPAGESIZES); + ATF_REQUIRE_MSG(pscnt != -1, "getpagesizes failed; errno=%d", errno); + ATF_REQUIRE_MSG(ps[0] != 0, "psind 0 is %zu", ps[0]); + ATF_REQUIRE_MSG(pscnt <= MAXPAGESIZES, "invalid pscnt %d", pscnt); + if (pscnt == 1 && required) + atf_tc_skip("no large page support"); + return (pscnt); +} + diff --git a/tests/sys/posixshm/posixshm_test.c b/tests/sys/posixshm/posixshm_test.c index 55514a5f4bde..680a443b6eac 100644 --- a/tests/sys/posixshm/posixshm_test.c +++ b/tests/sys/posixshm/posixshm_test.c @@ -49,6 +49,8 @@ #include <atf-c.h> +#include "posixshm.h" + #define TEST_PATH_LEN 256 static char test_path[TEST_PATH_LEN]; static char test_path2[TEST_PATH_LEN]; @@ -1239,20 +1241,6 @@ shm_open_large(int psind, int policy, size_t sz) return (fd); } -static int -pagesizes(size_t ps[MAXPAGESIZES]) -{ - int pscnt; - - pscnt = getpagesizes(ps, MAXPAGESIZES); - ATF_REQUIRE_MSG(pscnt != -1, "getpagesizes failed; errno=%d", errno); - ATF_REQUIRE_MSG(ps[0] != 0, "psind 0 is %zu", ps[0]); - ATF_REQUIRE_MSG(pscnt <= MAXPAGESIZES, "invalid pscnt %d", pscnt); - if (pscnt == 1) - atf_tc_skip("no large page support"); - return (pscnt); -} - ATF_TC_WITHOUT_HEAD(largepage_basic); ATF_TC_BODY(largepage_basic, tc) { @@ -1261,7 +1249,7 @@ ATF_TC_BODY(largepage_basic, tc) size_t ps[MAXPAGESIZES]; int error, fd, pscnt; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); zeroes = calloc(1, ps[0]); ATF_REQUIRE(zeroes != NULL); for (int i = 1; i < pscnt; i++) { @@ -1317,7 +1305,7 @@ ATF_TC_BODY(largepage_config, tc) size_t ps[MAXPAGESIZES + 1]; /* silence warnings if MAXPAGESIZES == 1 */ int error, fd; - (void)pagesizes(ps); + (void)pagesizes(ps, true); fd = shm_open(SHM_ANON, O_CREAT | O_RDWR, 0); ATF_REQUIRE_MSG(fd >= 0, "shm_open failed; error=%d", errno); @@ -1379,7 +1367,7 @@ ATF_TC_BODY(largepage_mmap, tc) size_t ps[MAXPAGESIZES]; int fd, pscnt; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { fd = shm_open_large(i, SHM_LARGEPAGE_ALLOC_DEFAULT, ps[i]); @@ -1475,7 +1463,7 @@ ATF_TC_BODY(largepage_munmap, tc) size_t ps[MAXPAGESIZES], ps1; int fd, pscnt; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { fd = shm_open_large(i, SHM_LARGEPAGE_ALLOC_DEFAULT, ps[i]); ps1 = ps[i - 1]; @@ -1526,7 +1514,7 @@ ATF_TC_BODY(largepage_madvise, tc) size_t ps[MAXPAGESIZES]; int fd, pscnt; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { fd = shm_open_large(i, SHM_LARGEPAGE_ALLOC_DEFAULT, ps[i]); addr = mmap(NULL, ps[i], PROT_READ | PROT_WRITE, MAP_SHARED, fd, @@ -1595,7 +1583,7 @@ ATF_TC_BODY(largepage_mlock, tc) "sysctlbyname(vm.stats.vm.v_user_wire_count) failed; error=%d", errno); - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { if (ps[i] / ps[0] > max_wired - wired) { /* Cannot wire past the limit. */ @@ -1638,7 +1626,7 @@ ATF_TC_BODY(largepage_msync, tc) size_t ps[MAXPAGESIZES]; int fd, pscnt; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { fd = shm_open_large(i, SHM_LARGEPAGE_ALLOC_DEFAULT, ps[i]); addr = mmap(NULL, ps[i], PROT_READ | PROT_WRITE, MAP_SHARED, fd, @@ -1697,7 +1685,7 @@ ATF_TC_BODY(largepage_mprotect, tc) size_t ps[MAXPAGESIZES]; int fd, pscnt; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { /* * Reserve a contiguous region in the address space to avoid @@ -1767,7 +1755,7 @@ ATF_TC_BODY(largepage_minherit, tc) pid_t child; int fd, pscnt, status; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { fd = shm_open_large(i, SHM_LARGEPAGE_ALLOC_DEFAULT, ps[i]); addr = mmap(NULL, ps[i], PROT_READ | PROT_WRITE, MAP_SHARED, fd, @@ -1855,7 +1843,7 @@ ATF_TC_BODY(largepage_pipe, tc) int fd, pfd[2], pscnt, status; pid_t child; - pscnt = pagesizes(ps); + pscnt = pagesizes(ps, true); for (int i = 1; i < pscnt; i++) { fd = shm_open_large(i, SHM_LARGEPAGE_ALLOC_DEFAULT, ps[i]); @@ -1908,7 +1896,7 @@ ATF_TC_BODY(largepage_reopen, tc) size_t ps[MAXPAGESIZES]; int fd, psind; - (void)pagesizes(ps); + (void)pagesizes(ps, true); psind = 1; gen_test_path();home | help
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