Hi John,

On 10/07/2019 10:47, Vincenzo Frascino wrote:

Hi John,

On 10/07/2019 05:02, John Stultz wrote:

quoted

On Fri, Jun 21, 2019 at 3:18 AM Vincenzo Frascino
[off-list ref] wrote:

quoted

Provide the arm64 compat (AArch32) vDSO in kernel/vdso32 in a similar
way to what happens in kernel/vdso.

The compat vDSO leverages on an adaptation of the arm architecture code
with few changes:
 - Use of lib/vdso for gettimeofday
 - Implementation of syscall based fallback
 - Introduction of clock_getres for the compat library
 - Implementation of trampolines
 - Implementation of elf note

To build the compat vDSO a 32 bit compiler is required and needs to be
specified via CONFIG_CROSS_COMPILE_COMPAT_VDSO.

Hey Vincenzo!
  Congrats on getting this work merged, I know its been a long effort
over a number of years!

Though unfortunately, it seems the arm64 vdso code that just landed is
breaking AOSP for me.

I see a lot of the following errors:
01-01 01:22:14.097   755   755 F libc    : Fatal signal 11 (SIGSEGV),
code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 755 (cameraserver),
pid 755 (cameraserver)
01-01 01:22:14.112   759   759 F libc    : Fatal signal 11 (SIGSEGV),
code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 759
(android.hardwar), pid 759 (android.hardwar)
01-01 01:22:14.120   756   756 F libc    : Fatal signal 11 (SIGSEGV),
code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 756 (drmserver),
pid 756 (drmserver)

Which go away if I revert the vdso merge that went in via tip/timers.

I tried to bisect things down a bit, but as some later fixes are
required (at one point, date was returning the start epoch and never
increasing), this hasn't worked too well. But I'm guessing since I
see: "CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will
not be built", and the system is half working, I'm guessing this is an
issue with just the 32bit code failing.  While I can try to sort out
the proper CROSS_COMPILE_COMPAT in my build environment, I assume
userland shouldn't be crashing if that value isn't set.

Any chance this issue has already been raised?

I do not have Android (bionic/libc) as part of my testing environment hence I
never saw this issue. Thanks for reporting it.

I am investigating the problem and will post a fix as soon as it is ready.

As Will suggested, .config would help the debugging and I would like to ask to
you to test my fix once it is ready. Is that OK for you?

quoted

thanks
-john

Seems that the problem you are experiencing is caused by an ABI regression for
which I provided a fix in [1]. Could you please verify that works for you as well?

[1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2046889.html

Please find below the tests that I conducted to verify that when
CROSS_COMPILE_COMPAT is not defined or empty the compat vdso library is not exposed.

# cat main-arm32.c

#include <stdio.h>
#include <sys/auxv.h>

int main()
{
	uintptr_t vdso = (uintptr_t) getauxval(AT_SYSINFO_EHDR);

	printf("AT_SYSINFO_EHDR: %p\n", vdso);

[...]

	return 0;
}

# file main-arm32
main-arm32: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically
linked, interpreter /lib/ld-, for GNU/Linux 3.2.0, with d

When CROSS_COMPILE_COMPAT is _not_ defined:
===========================================

# ./main-arm32
AT_SYSINFO_EHDR: (nil)

Memory Map:
-----------

00008000-00010000 rw-p 00000000 00:00 0
00010000-00011000 r-xp 00000000 00:13 24905929 /home/vinfra01/bin/main-arm32
00011000-00020000 rw-p 00000000 00:00 0
00020000-00021000 r--p 00000000 00:13 24905929 /home/vinfra01/bin/main-arm32
00021000-00022000 rw-p 00001000 00:13 24905929 /home/vinfra01/bin/main-arm32
00022000-f773d000 rw-p 00000000 00:00 0        [heap]
f773d000-f781f000 r-xp 00000000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f781f000-f782f000 ---p 000e2000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f782f000-f7831000 r--p 000e2000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f7831000-f7832000 rw-p 000e4000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f7832000-f7835000 rw-p 00000000 00:00 0
f7835000-f784b000 rw-p 00000000 00:00 0
f784b000-f7863000 r-xp 00000000 00:13 24906908 /lib/arm-linux-gnueabihf/ld-2.27.so
f7863000-f7870000 rw-p 00000000 00:00 0
f7870000-f7872000 rw-p 00000000 00:00 0
f7872000-f7873000 r-xp 00000000 00:00 0        [sigpage]
f7873000-f7874000 r--p 00018000 00:13 24906908 /lib/arm-linux-gnueabihf/ld-2.27.so
f7874000-f7875000 rw-p 00019000 00:13 24906908 /lib/arm-linux-gnueabihf/ld-2.27.so
f7875000-ff77a000 rw-p 00000000 00:00 0
ff87a000-ff89b000 rw-p 00000000 00:00 0        [stack]
ff89b000-ffff0000 rw-p 00000000 00:00 0
ffff0000-ffff1000 r-xp 00000000 00:00 0        [vectors]
ffff1000-fffff000 rw-p 00000000 00:00 0


vdsotest for compat [2]:
------------------------

Note: vDSO version of clock_gettime not found
clock-gettime-monotonic: syscall: 796 nsec/call
clock-gettime-monotonic:    libc: 816 nsec/call
clock-gettime-monotonic:    vdso: not tested
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_getres not found
clock-getres-monotonic: syscall: 567 nsec/call
clock-getres-monotonic:    libc: 581 nsec/call
clock-getres-monotonic:    vdso: not tested
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_gettime not found
clock-gettime-monotonic-coarse: syscall: 617 nsec/call
clock-gettime-monotonic-coarse:    libc: 656 nsec/call
clock-gettime-monotonic-coarse:    vdso: not tested
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_getres not found
clock-getres-monotonic-coarse: syscall: 591 nsec/call
clock-getres-monotonic-coarse:    libc: 614 nsec/call
clock-getres-monotonic-coarse:    vdso: not tested
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_gettime not found
clock-gettime-realtime: syscall: 819 nsec/call
clock-gettime-realtime:    libc: 858 nsec/call
clock-gettime-realtime:    vdso: not tested
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_getres not found
clock-getres-realtime: syscall: 567 nsec/call
clock-getres-realtime:    libc: 583 nsec/call
clock-getres-realtime:    vdso: not tested
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_gettime not found
clock-gettime-realtime-coarse: syscall: 599 nsec/call
clock-gettime-realtime-coarse:    libc: 638 nsec/call
clock-gettime-realtime-coarse:    vdso: not tested
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_gettime not found
Note: vDSO version of clock_getres not found
clock-getres-realtime-coarse: syscall: 591 nsec/call
clock-getres-realtime-coarse:    libc: 610 nsec/call
clock-getres-realtime-coarse:    vdso: not tested
Note: vDSO version of clock_getres not found
Note: vDSO version of clock_getres not found
Note: vDSO version of getcpu not found
getcpu: syscall: 431 nsec/call
getcpu:    libc: 451 nsec/call
getcpu:    vdso: not tested
Note: vDSO version of getcpu not found
Note: vDSO version of getcpu not found
Note: vDSO version of gettimeofday not found
gettimeofday: syscall: 765 nsec/call
gettimeofday:    libc: 808 nsec/call
gettimeofday:    vdso: not tested
Note: vDSO version of gettimeofday not found
Note: vDSO version of gettimeofday not found

When CROSS_COMPILE_COMPAT is defined:
=====================================

# ./main-arm32
AT_SYSINFO_EHDR: 0xf7a67000

Memory map:
-----------

00008000-00010000 rw-p 00000000 00:00 0
00010000-00011000 r-xp 00000000 00:13 24905929 /home/vinfra01/bin/main-arm32
00011000-00020000 rw-p 00000000 00:00 0
00020000-00021000 r--p 00000000 00:13 24905929 /home/vinfra01/bin/main-arm32
00021000-00022000 rw-p 00001000 00:13 24905929 /home/vinfra01/bin/main-arm32
00022000-f7932000 rw-p 00000000 00:00 0        [heap]
f7932000-f7a14000 r-xp 00000000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f7a14000-f7a24000 ---p 000e2000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f7a24000-f7a26000 r--p 000e2000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f7a26000-f7a27000 rw-p 000e4000 00:13 24906912 /lib/arm-linux-gnueabihf/libc-2.27.so
f7a27000-f7a2a000 rw-p 00000000 00:00 0
f7a2a000-f7a40000 rw-p 00000000 00:00 0
f7a40000-f7a58000 r-xp 00000000 00:13 24906908 /lib/arm-linux-gnueabihf/ld-2.27.so
f7a58000-f7a64000 rw-p 00000000 00:00 0
f7a64000-f7a66000 rw-p 00000000 00:00 0
f7a66000-f7a67000 r--p 00000000 00:00 0        [vvar]
f7a67000-f7a68000 r-xp 00000000 00:00 0        [vdso]
f7a68000-f7a69000 r--p 00018000 00:13 24906908 /lib/arm-linux-gnueabihf/ld-2.27.so
f7a69000-f7a6a000 rw-p 00019000 00:13 24906908 /lib/arm-linux-gnueabihf/ld-2.27.so
f7a6a000-ff6d8000 rw-p 00000000 00:00 0
ff7d8000-ff7f9000 rw-p 00000000 00:00 0        [stack]
ff7f9000-ffff0000 rw-p 00000000 00:00 0
ffff0000-ffff1000 r-xp 00000000 00:00 0        [vectors]
ffff1000-fffff000 rw-p 00000000 00:00 0

vdsotest for compat [2]:
------------------------

clock-gettime-monotonic: syscall: 700 nsec/call
clock-gettime-monotonic:    libc: 226 nsec/call
clock-gettime-monotonic:    vdso: 189 nsec/call
clock-getres-monotonic: syscall: 582 nsec/call
clock-getres-monotonic:    libc: 581 nsec/call
clock-getres-monotonic:    vdso: 40 nsec/call
clock-gettime-monotonic-coarse: syscall: 618 nsec/call
clock-gettime-monotonic-coarse:    libc: 103 nsec/call
clock-gettime-monotonic-coarse:    vdso: 85 nsec/call
clock-getres-monotonic-coarse: syscall: 602 nsec/call
clock-getres-monotonic-coarse:    libc: 610 nsec/call
clock-getres-monotonic-coarse:    vdso: 64 nsec/call
clock-gettime-realtime: syscall: 741 nsec/call
clock-gettime-realtime:    libc: 209 nsec/call
clock-gettime-realtime:    vdso: 189 nsec/call
clock-getres-realtime: syscall: 627 nsec/call
clock-getres-realtime:    libc: 604 nsec/call
clock-getres-realtime:    vdso: 41 nsec/call
clock-gettime-realtime-coarse: syscall: 640 nsec/call
clock-gettime-realtime-coarse:    libc: 105 nsec/call
clock-gettime-realtime-coarse:    vdso: 84 nsec/call
clock-getres-realtime-coarse: syscall: 597 nsec/call
clock-getres-realtime-coarse:    libc: 608 nsec/call
clock-getres-realtime-coarse:    vdso: 46 nsec/call
Note: vDSO version of getcpu not found
getcpu: syscall: 492 nsec/call
getcpu:    libc: 492 nsec/call
getcpu:    vdso: not tested
Note: vDSO version of getcpu not found
Note: vDSO version of getcpu not found
gettimeofday: syscall: 664 nsec/call
gettimeofday:    libc: 224 nsec/call
gettimeofday:    vdso: 185 nsec/call

[2] https://github.com/nathanlynch/vdsotest

-- 
Regards,
Vincenzo

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