Hi Alex, > Lukasz Majewski <lu...@denx.de> writes: > > > Dear Qemu Community, > > > > I would like to ask you for some advice regarding the usage of > > arm-linux-user/qemu-arm user space program simulation. > > > > Background: > > ----------- > > > > I'm looking for a way to efficiently test y2038 in-glibc solution > > for 32 bit architectures (e.g. ARM). > > > > For now I do use qemu-system-arm (part of Yocto/OE), which I'm > > using to run Linux kernel 5.1, glibc under test and Y2038 tests. It > > works [1]. > > > > Problem: > > -------- > > > > I would like to test cross-compiled tests (which are built from > > glibc sources) without the need to run the emulated system with > > qemu-system-arm. > > > > I've come across the "QEMU user mode", which would execute the > > cross-compiled test (with already cross-compiled glibc via -L > > switch) and just return exit status code. This sounds appealing. > > > > As fair as I've read - QEMU user mode emulates ARM syscalls. > > It's not strictly an emulation - it is more of a guided pass-through. > QEMU may tweak details like re-arranging structures or handling > byte-swapping but ultimately the syscall is passed down to the host > system.
This means that clock_settime64 will run clock_settime on the host system (x86_64 in my case) and adjust its time. My goal is to avoid adjusting host time in any way. > > > During test execution (single qemu user mode process) I would need > > to adjust date with clock_settime64 syscall and then execute other > > syscalls if needed. > > This will set the time on your host system. Ok. Thanks for the clarification. > > > Please correct me if I'm wrong: > > - It looks like qemu-arm doesn't have switch which would allow it to > > set time offset (to e.g. year 2039 - something similar to > > qemu-system-arm -rtc=). > > No - most of the command line switches pertain to memory layout and > how libraries are searched for. The details of the results of system > calls are very much left up to the host. > > > > > - As of 5.1 qemu version there is no support for syscalls > > supporting 64 bit time on 32 bit architectures (e.g. > > clock_settime64 and friends from [2]). > > Hmm since 5bcb4986384e02669418a411cac10377cf48e698 the syscall table > has had mappings for all of those: > > # 402 is unused > 403 common clock_gettime64 > sys_clock_gettime 404 common clock_settime64 > sys_clock_settime 405 common > clock_adjtime64 sys_clock_adjtime > Ok. I've been using v5.1.0 instead of -master branch. > > > > For my example program [3] statically build for testing (it works > > with qemu-system-arm): > > > > ~/work/qemu-arm-tests-program$ > > ../qemu-5.1.0-arm/arm-linux-user/qemu-arm -L > > ~/work/yocto/y2038/build/tmp/armv7at2hf-neon-poky-linux-gnueabi/y2038-glibc/2.30+git999-r0/image/opt > > -strace ./cst > > > > 17746 brk(NULL) = 0x00074000 > > 17746 brk(0x000748a8) = 0x000748a8 > > 17746 uname(0x40800370) = 0 > > 17746 readlink("/proc/self/exe",0x407ff488,4096) = 43 > > 17746 brk(0x000958a8) = 0x000958a8 > > 17746 brk(0x00096000) = 0x00096000 > > 17746 mprotect(0x00070000,8192,PROT_READ) = 0 > > 17746statx(1,"",AT_EMPTY_PATH|AT_NO_AUTOMOUNT,STATX_BASIC_STATS,0x407ffd70) > > = 0 > > 17746 Unknown syscall 404 --> is the syscall number of > > clock_settime64 > > > > 17746 dup(2) = 3 > > 17746 fcntl64(3,F_GETFL) = 2 > > 17746statx(3,"",AT_EMPTY_PATH|AT_NO_AUTOMOUNT,STATX_BASIC_STATS,0x407ff8e8) > > = 0 ERR > > > > Questions: > > ---------- > > > > 1. Is there any plan to add support for emulating syscalls > > supporting 64 bit time on 32 bit architectures [2]? > > It's certainly a bug if it's not working for you. > > > > > 2. Provide QEMU user space switch to adjust its time (i.e. add some > > offset to in-fly emulated time syscalls - like clock_settime64) > > when it is started? > > Unlikely - but you could carry a local patch for your own purposes. > My goal would be to test if syscalls with 64 bit time (e.g. struct timespec) work correctly, so I would need to adjust many syscalls as I do test for example if futex change times out. It looks like having Yocto/OE crafted BSP with qemu-system-arm is a better solution as I do have proper syscalls support out of the box. Anyway, big thanks for the clarification. Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lu...@denx.de
pgpvZ5pcPUEtY.pgp
Description: OpenPGP digital signature