Date: Sat, 5 Jan 2019 17:14:27 -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>, freebsd-arm <freebsd-arm@freebsd.org> Subject: qemu-arm-static has target_shmd_ds too small vs. arm native's shmid_ds Message-ID: <6B222E96-A644-46A7-9D1C-D164ED465631@yahoo.com>
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[The context here is FreeBSD head -r341836 based and ports head -r488859 =
based.]
Note: I assume that "struct target_shmd_ds" is meant to match the memory =
layout
of the target's native "struct shmid_ds". Otherwise the reported =
differences
below could be irrelevant.
For armv7 (and likely armv6) the following code:
printf("sizeof(struct shmid_ds) =3D %lu\n", (unsigned long) =
sizeof(struct shmid_ds));
printf("shm_perm %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_perm));
printf("shm_segsz %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_segsz));
printf("shm_lpid %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_lpid));
printf("shm_cpid %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_cpid));
printf("shm_nattch %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_nattch));
printf("shm_atime %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_atime));
printf("shm_dtime %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_dtime));
printf("shm_ctime %lu\n", (unsigned long) offsetof(struct =
shmid_ds, shm_ctime));
produces:
sizeof(struct shmid_ds) =3D 64
shm_perm 0
shm_segsz 24
shm_lpid 28
shm_cpid 32
shm_nattch 36
shm_atime 40
shm_dtime 48
shm_ctime 56
However gdb reports for qemu-arm-static (on amd64):
(gdb) p/d &((struct target_shmid_ds *)0)->shm_perm
$33 =3D 0
(gdb) p/d &((struct target_shmid_ds *)0)->shm_segsz
$34 =3D 24
(gdb) p/d &((struct target_shmid_ds *)0)->shm_lpid=20
$35 =3D 28
(gdb) p/d &((struct target_shmid_ds *)0)->shm_cpid
$36 =3D 32
(gdb) p/d &((struct target_shmid_ds *)0)->shm_nattch
$37 =3D 36
(gdb) p/d &((struct target_shmid_ds *)0)->shm_atime=20
$38 =3D 40
(gdb) p/d &((struct target_shmid_ds *)0)->shm_dtime
$39 =3D 44
(gdb) p/d &((struct target_shmid_ds *)0)->shm_ctime
$40 =3D 48
so after shm_atime the offsets are different.
/usr/include/sys/shm.h has:
struct shmid_ds {
struct ipc_perm shm_perm; /* operation permission =
structure */
size_t shm_segsz; /* size of segment in bytes */
pid_t shm_lpid; /* process ID of last shared memory =
op */
pid_t shm_cpid; /* process ID of creator */
shmatt_t shm_nattch; /* number of current attaches */
time_t shm_atime; /* time of last shmat() */
time_t shm_dtime; /* time of last shmdt() */
time_t shm_ctime; /* time of last change by =
shmctl() */
};
=
/wrkdirs/usr/ports/emulators/qemu-user-static/work/qemu-bsd-user-4ef7d07/b=
sd-user/syscall_defs.h
has:
struct target_shmid_ds {
struct target_ipc_perm shm_perm; /* peration permission structure =
*/
abi_ulong shm_segsz; /* size of segment in bytes */
int32_t shm_lpid; /* process ID of last shared memory op */
int32_t shm_cpid; /* process ID of creator */
int32_t shm_nattch; /* number of current attaches */
abi_ulong shm_atime; /* time of last shmat() */
abi_ulong shm_dtime; /* time of last shmdt() */
abi_ulong shm_ctime; /* time of last change by shmctl() */
};
abi_ulong's for shm_atime, shm_dtime, and shm_ctime are the wrong
size for armv7: arm uses 64-bit time_t. As of 12+ only i386
uses 32-bit time_t if I understand right. In 11.x 32-bit powerpc
also uses 32-bit time_t.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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