Hi Alistair, > On Tue, Nov 3, 2020 at 8:55 AM Lukasz Majewski <lu...@denx.de> wrote: > > > > Hi Alistair, > > > > > On Tue, Nov 3, 2020 at 3:03 AM Lukasz Majewski <lu...@denx.de> > > > wrote: > > > > > > > > Dear Qemu Community, > > > > > > Hey Lukasz, > > > > > > + QEMU Dev Mailing list > > > + Laurent > > > > > > > Thanks for reaching more people. > > > > > > > > > > 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 another advantage it is much, much faster at running the glibc > > > tests. > > > > > > > +1 > > > > > > > > > > As fair as I've read - QEMU user mode emulates ARM syscalls. > > > > > > > > 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. > > > > > > > > > > > > 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=). > > > > > > > > - 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]). > > > > > > There is some support in the current master, for example > > > __NR_futex_time64 is supported. > > > > I've just looked into v5.1.0 stable release. I will double check > > this with -master branch. > > > > > > > > I started to add some support for RV32 once it was merged into > > > glibc. > > > > Ok. > > > > > > > > > > > > > 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 > > > > > > clock_settime64 is supported in master QEMU. > > > > I will double check it - thanks for pointing this out. > > > > > > > > > > > > > 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]? > > > > > > I would like to have RV32 supported, but it's a low priority for > > > me. > > > > Having syscalls supporting 64 bit time on 32 bit machines indicated > > in [2] would be a very welcome for glibc testing. > > > > > I > > > expect it's something that will eventually happen though. > > > > Ok. > > > > > > > > > > > > > 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? > > > > > > That I'm not sure about. > > > > For me it would be enough to have: > > > > qemu-arm -rtc="2039-01-01" -L... ./ctx > > So the emulated "time" would be after 32 bit time_t overflow when > > QEMU user space emulation process starts (as long as it doesn't > > touch the host machine time). > > > > > > Another option (workaround) would be to run clock_settime64() with > > time set to year 2038+ on the beginning of each glibc test. It > > shall work as long as we don't change host time (and all time > > changes would stay in the qemu user mode process). > > > > > I assume just running date/clock_settime64 > > > from a script wouldn't work with the glibc test framework? > > > > Could you elaborate on this use case/scenario? Do you have some > > examples to share? > > Whoops, I got confused here. The clock_gettime syscall goes to the > host, so we just report host time. I was thinking about softMMU where > we maintain our own time. > > So your proposed `-rtc` command would add an offset to the host time? > Something like: > > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > index 3160a9ba06..240bd59bb2 100644 > --- a/linux-user/syscall.c > +++ b/linux-user/syscall.c > @@ -12074,6 +12074,7 @@ static abi_long do_syscall1(void *cpu_env, int > num, abi_long arg1, > > ret = target_to_host_timespec64(&ts, arg2); > if (!is_error(ret)) { > + ts.tv_sec -= 567993505; > ret = get_errno(clock_settime(arg1, &ts)); > } > return ret; > @@ -12096,6 +12097,8 @@ static abi_long do_syscall1(void *cpu_env, int > num, abi_long arg1, > struct timespec ts; > ret = get_errno(clock_gettime(arg1, &ts)); > if (!is_error(ret)) { > + // Calculate different to same time in 2038 > + ts.tv_sec += 567993505; > ret = host_to_target_timespec64(arg2, &ts); > } > return ret; > > That might end up working if you can intercept all of the absolute > time syscalls.
It looks to me that intercepting _all_ time related syscalls seems to be a time consuming task. > > Without any mainline support that would be easy to do in your local > tree, The "local tree" solution is not an acceptable solution for me. > which would at least allow you to test. You could also change > your host time to 2038, but that would break things for your host. Yes, I would like to avoid changing the host time. > > Alistair > > > > > > > > > Alistair > > > > > > > > > > > > > > > Thanks in advance for your help and reply. > > > > > > > > > > > > Links: > > > > [1] - https://github.com/lmajewski/meta-y2038/ > > > > [2] - > > > > https://elixir.bootlin.com/linux/latest/source/arch/arm/tools/syscall.tbl#L419 > > > > > > > > [3]: > > > > Example program: > > > > cat <<- EOF >> clock_settime_test.c > > > > #include <stdio.h> > > > > #include <time.h> > > > > > > > > int main (int argc, char **argv) > > > > { > > > > struct timespec tv; > > > > int ret; > > > > > > > > tv.tv_sec = 0x7FFFFFFF; > > > > tv.tv_sec += 61; > > > > tv.tv_nsec = 0; > > > > > > > > printf("clock_settime test program: "); > > > > ret = clock_settime(CLOCK_REALTIME, &tv); > > > > if (!ret) > > > > printf("OK\n"); > > > > else > > > > perror("ERR\n"); > > > > > > > > return 0; > > > > } > > > > EOF > > > > > > > > Build the test program: > > > > gcc -Wall -ggdb -D_TIME_BITS=64 -D_FILE_OFFSET_BITS=64 > > > > -I/opt/include -I/opt/usr/include -L/opt/usr/lib \ > > > > -Wl,-rpath=/opt/lib -Wl,--dynamic-linker=/opt/lib/ld-linux.so.2 > > > > clock_settime_test.c -o cst -static > > > > > > > > > > > > > > > > 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 > > > > > > > > > > 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 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
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