Date: Sun, 30 Dec 2018 17:26:01 -0800 From: Mark Millard <marklmi@yahoo.com> To: mmel@freebsd.org Cc: freebsd-emulation@freebsd.org, FreeBSD Current <freebsd-current@freebsd.org>, ports-list freebsd <freebsd-ports@freebsd.org>, freebsd-arm <freebsd-arm@freebsd.org>, FreeBSD Toolchain <freebsd-toolchain@freebsd.org> Subject: Re: A reliable port cross-build failure (hangup) in my context (amd64->armv7 cross build, with native-tool speedup involved) [details of a specific qemu-arm-static source code problem] Message-ID: <A6CDEEBE-1753-4D28-9F9C-90E7789BB7D2@yahoo.com> In-Reply-To: <CD78D55F-9B73-4914-9E7A-41590F058B03@yahoo.com> References: <FF9B4284-4E6B-4D36-86A0-18861B527AC0@yahoo.com> <865A13C8-9749-486E-9F79-5EEDDECBE621@yahoo.com> <0154C3AC-D85B-4FCF-BA63-454BC26BC1A2@yahoo.com> <A6A58CE3-062B-4B79-A8C2-ADFDAA04C6AF@yahoo.com> <13f5e4dd-33fb-2170-e31a-1b5d5f155869@freebsd.org> <ABA957EA-B8EE-4B8C-9C2F-B745BA652BF6@yahoo.com> <2E3F6196-4652-40D2-937F-8860B6005A35@yahoo.com> <CD78D55F-9B73-4914-9E7A-41590F058B03@yahoo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
[Removing __packed did make the size and offsets match armv7
and the build worked based on the reconstructed qemu-arm-static.]
On 2018-Dec-30, at 16:38, Mark Millard <marklmi@yahoo.com> wrote:
> On 2018-Dec-28, at 12:12, Mark Millard <marklmi at yahoo.com> wrote:
>=20
>> On 2018-Dec-28, at 05:13, Michal Meloun <melounmichal at gmail.com> =
wrote:
>>=20
>>> Mark,
>>> this is known problem with qemu-user-static.
>>> Emulation of every single interruptible syscall is broken by design =
(it
>>> have signal related races). Theses races cannot be solved without =
major
>>> rewrite of syscall emulation code.
>>> Unfortunately, nobody actively works on this, I think.
>>>=20
>>=20
>> Thanks for the note setting some expectations.
>> . . .
>=20
>=20
> It turns out that I've been through (part of?) this before and
> mikael.urankar@gmail.com had back then provided a qemu-user-static
> patch (that might have been arm specific or 32-bit target specific
> when running on a 64-bit host). (The qemu-user-static code structure
> seems to have changed some afterwards and the patch is no longer
> where he had pointed me to back then.)
>=20
> To show size and offsets on armv7 vs. armd64 for struct kevent
> I use:
>=20
> # more kevent_size_offsets.c=20
> #include "/usr/include/sys/event.h" // kevent
> #include <stddef.h> // offsetof
> #include <stdio.h> // printf
>=20
> int
> main()
> {
> printf("%lu\n", (unsigned long) sizeof(struct kevent));
> printf("ident %lu\n", (unsigned long) offsetof(struct kevent, =
ident));
> printf("filter %lu\n", (unsigned long) offsetof(struct kevent, =
filter));
> printf("flags %lu\n", (unsigned long) offsetof(struct kevent, =
flags));
> printf("fflags %lu\n", (unsigned long) offsetof(struct kevent, =
fflags));
> printf("data %lu\n", (unsigned long) offsetof(struct kevent, =
data));
> printf("udata %lu\n", (unsigned long) offsetof(struct kevent, =
udata));
> printf("ext %lu\n", (unsigned long) offsetof(struct kevent, =
ext));
> return 0;
> }
>=20
> It ends up showing on armv7 (under qemu-arm-static insteead of native, =
not
> that it matters here):
>=20
> # ./a.out
> 64
> ident 0
> filter 4
> flags 6
> fflags 8
> data 16
> udata 24
> ext 32
>=20
> On amd64 (native) it ends up as:
>=20
> # ./a.out
> 64
> ident 0
> filter 8
> flags 10
> fflags 12
> data 16
> udata 24
> ext 32
>=20
> Thus a translation of layout is required when hosted. This is for:
>=20
> struct kevent {
> __uintptr_t ident; /* identifier for this event */
> short filter; /* filter for event */
> unsigned short flags; /* action flags for kqueue */
> unsigned int fflags; /* filter flag value */
> __int64_t data; /* filter data value */
> void *udata; /* opaque user data identifier =
*/
> __uint64_t ext[4]; /* extensions */
> };
>=20
> But qemu-user-static has for translation purposes:
>=20
> struct target_freebsd_kevent {
> abi_ulong ident;
> int16_t filter;
> uint16_t flags;
> uint32_t fflags;
> int64_t data;
> abi_ulong udata;
> uint64_t ext[4];
> } __packed;
>=20
> (note the __packed) for which in amd64's qemu_arm_static has
> the size and offsets:
>=20
> # gdb qemu-arm-static
> . . .
> (gdb) p/d sizeof(struct target_freebsd_kevent)
> $1 =3D 56
> (gdb) p/d &((struct target_freebsd_kevent *)0)->ident
> $2 =3D 0
> (gdb) p/d &((struct target_freebsd_kevent *)0)->filter
> $3 =3D 4
> (gdb) p/d &((struct target_freebsd_kevent *)0)->flags
> $4 =3D 6
> (gdb) p/d &((struct target_freebsd_kevent *)0)->fflags
> $5 =3D 8
> (gdb) p/d &((struct target_freebsd_kevent *)0)->data
> $6 =3D 12
> (gdb) p/d &((struct target_freebsd_kevent *)0)->udata
> $7 =3D 20
> (gdb) p/d &((struct target_freebsd_kevent *)0)->ext
> $8 =3D 24
>=20
> which which does not match the armv7 offsets for
> data, udata, or ext and does not have the right size
> for struct target_freebsd_kevent[] indexing to
> match armv7's struct target_freebsd_kevent[] indexing.
>=20
> This in turn makes the do_freebsd_kevent code do the wrong
> thing in its:
>=20
> struct target_freebsd_kevent *target_changelist, *target_eventlist;
> . . .
> for (i =3D 0; i < arg3; i++) {
> __get_user(changelist[i].ident, =
&target_changelist[i].ident);
> __get_user(changelist[i].filter, =
&target_changelist[i].filter);
> __get_user(changelist[i].flags, =
&target_changelist[i].flags);
> __get_user(changelist[i].fflags, =
&target_changelist[i].fflags);
> __get_user(changelist[i].data, &target_changelist[i].data);
> /* __get_user(changelist[i].udata, =
&target_changelist[i].udata); */
> #if TARGET_ABI_BITS =3D=3D 32
> changelist[i].udata =3D (void =
*)(uintptr_t)target_changelist[i].udata;
> tswap32s((uint32_t *)&changelist[i].udata);
> #else
> changelist[i].udata =3D (void =
*)(uintptr_t)target_changelist[i].udata;
> tswap64s((uint64_t *)&changelist[i].udata);
> #endif
> __get_user(changelist[i].ext[0], =
&target_changelist[i].ext[0]);
> __get_user(changelist[i].ext[1], =
&target_changelist[i].ext[1]);
> __get_user(changelist[i].ext[2], =
&target_changelist[i].ext[2]);
> __get_user(changelist[i].ext[3], =
&target_changelist[i].ext[3]);
> }
> . . .
> for (i =3D 0; i < arg5; i++) {
> __put_user(eventlist[i].ident, &target_eventlist[i].ident);
> __put_user(eventlist[i].filter, =
&target_eventlist[i].filter);
> __put_user(eventlist[i].flags, &target_eventlist[i].flags);
> __put_user(eventlist[i].fflags, =
&target_eventlist[i].fflags);
> __put_user(eventlist[i].data, &target_eventlist[i].data);
> /* __put_user(eventlist[i].udata, =
&target_eventlist[i].udata);*/
> #if TARGET_ABI_BITS =3D=3D 32
> tswap32s((uint32_t *)&eventlist[i].data);
> target_eventlist[i].data =3D (uintptr_t)eventlist[i].data;
> #else
> tswap64s((uint64_t *)&eventlist[i].data);
> target_eventlist[i].data =3D (uintptr_t)eventlist[i].data;
> #endif
> __put_user(eventlist[i].ext[0], =
&target_eventlist[i].ext[0]);
> __put_user(eventlist[i].ext[1], =
&target_eventlist[i].ext[1]);
> __put_user(eventlist[i].ext[2], =
&target_eventlist[i].ext[2]);
> __put_user(eventlist[i].ext[3], =
&target_eventlist[i].ext[3]);
> }
>=20
>=20
>=20
> I'll eventually do something to have struct target_freebsd_kevent for
> amd64-native targeting armv7 and see if that is sufficient to avoid =
the
> problem in my context. Previously removing the __packed was enough to
> make the structure the same size with the same offsets as for armv7.
> (Such might not have been appropriate to all targets.)
>=20
> armv6 would have the same problem as I understand things.
Using commented out __packed in:
struct target_freebsd11_kevent {
abi_ulong ident;
int16_t filter;
uint16_t flags;
uint32_t fflags;
abi_long data;
abi_ulong udata;
} ; // __packed;
struct target_freebsd_kevent {
abi_ulong ident;
int16_t filter;
uint16_t flags;
uint32_t fflags;
int64_t data;
abi_ulong udata;
uint64_t ext[4];
} ; // __packed;
in =
/wrkdirs/usr/ports/emulators/qemu-user-static/work/qemu-bsd-user-4ef7d07/b=
sd-user/syscall_defs.h
was sufficient to allow the multimedia/gstreamer1-qt@qt5 build to =
complete: no more hang-up.
So this is likely what is wrong for the packages-builders as well.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?A6CDEEBE-1753-4D28-9F9C-90E7789BB7D2>