Date: Fri, 4 Jan 2019 20:51:46 -0800 From: Mark Millard <marklmi@yahoo.com> To: Kyle Evans <kevans@FreeBSD.org>, freebsd-emulation@freebsd.org, ports-list freebsd <freebsd-ports@freebsd.org> Cc: Sean Bruno <sbruno@freebsd.org> Subject: Re: qemu-x86_64-static has target_freebsd_flock being too small (__packed use issue) [subject correction: fixed to be "too small"] Message-ID: <B9B82495-F526-4CA0-B0C1-AC6048572819@yahoo.com> In-Reply-To: <1139EAD0-FED3-428C-AA0E-00ABB8BD111D@yahoo.com> References: <1139EAD0-FED3-428C-AA0E-00ABB8BD111D@yahoo.com>
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[Just correcting the "larger" to be "smaller".]
On 2019-Jan-4, at 19:29, Mark Millard <marklmi@yahoo.com> wrote:
[qemu-aarch64-static has the same problem but qemu-armv7-sstatic does =
not. The context here
is FreeBSD head -r341836 based and ports head -r488859 based.]
Note: I assume that "struct target_freebsd_flock" is meant to match the =
memory layout
of the target's native "struct flock". Otherwise the reported =
differences
below could be irrelevant.
For amd64 and aarch64 the following code:
printf("sizeof(struct flock) =3D %lu\n", (unsigned long) =
sizeof(struct flock));
printf("l_start %lu\n", (unsigned long) offsetof(struct flock, =
l_start));
printf("l_len %lu\n", (unsigned long) offsetof(struct flock, =
l_len));
printf("l_pid %lu\n", (unsigned long) offsetof(struct flock, =
l_pid));
printf("l_type %lu\n", (unsigned long) offsetof(struct flock, =
l_type));
printf("l_whence %lu\n", (unsigned long) offsetof(struct flock, =
l_whence));
printf("l_sysid %lu\n", (unsigned long) offsetof(struct flock, =
l_sysid));
produces:
sizeof(struct flock) =3D 32
l_start 0
l_len 8
l_pid 16
l_type 20
l_whence 22
l_sysid 24
However gdb reports for qemu-x86_64-static and qemu-aarch64-static
and qemu-arm-static:
(gdb) p/d sizeof(struct target_freebsd_flock)
$10 =3D 28
(gdb) p/d &((struct target_freebsd_flock *)0)->l_start =20
$11 =3D 0
(gdb) p/d &((struct target_freebsd_flock *)0)->l_len =20
$12 =3D 8
(gdb) p/d &((struct target_freebsd_flock *)0)->l_pid
$13 =3D 16
(gdb) p/d &((struct target_freebsd_flock *)0)->l_type
$14 =3D 20
(gdb) p/d &((struct target_freebsd_flock *)0)->l_whence
$15 =3D 22
(gdb) p/d &((struct target_freebsd_flock *)0)->l_sysid=20
$16 =3D 24
So only the overall size is different for this information. But:
struct target_freebsd_flock {
int64_t l_start;
int64_t l_len;
int32_t l_pid;
int16_t l_type;
int16_t l_whence;
int32_t l_sysid;
} QEMU_PACKED;
with a potential packed vs. /usr/include/sys/fcntl.h :
struct flock {
off_t l_start; /* starting offset */
off_t l_len; /* len =3D 0 means until end of file */
pid_t l_pid; /* lock owner */
short l_type; /* lock type: read/write, etc. */
short l_whence; /* type of l_start */
int l_sysid; /* remote system id or zero for local */
};
with no potential __packed.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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