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Date: Wed, 16 Feb 2022 20:44:03 -0500
From: Satadru Pramanik <satadru@...il.com>
To: Rich Felker <dalias@...ifal.cx>
Cc: musl@...ts.openwall.com
Subject: Re: Re: musl getaddr info breakage on older kernels
Looks like I need to do more than just reverse that commit to get this to
build...
../src_musl/src/internal/syscall.h:47:53: note: in expansion of macro
‘__socketcall_cp’ 47 | #define socketcall_cp(nm,a,b,c,d,e,f)
__syscall_ret(__socketcall_cp(nm,a,b,c,d,e,f))
|
^~~~~~~~~~~~~~~
../src_musl/src/network/accept.c:6:16: note: in expansion of macro
‘socketcall_cp’
6 | return socketcall_cp(accept, fd, addr, len, 0, 0, 0);
| ^~~~~~~~~~~~~
../src_musl/src/internal/syscall.h:62:54: note: each undeclared identifier
is reported only once for each function it appears in
62 | #define __socketcall_cp(nm,a,b,c,d,e,f)
__syscall_cp(SYS_##nm, a, b, c, d, e, f) |
^~~~
../src_musl/src/internal/syscall.h:55:53: note: in definition of macro
‘__syscall_cp6’ 55 | #define __syscall_cp6(n,a,b,c,d,e,f)
(__syscall_cp)(n,__scc(a),__scc(b),__scc(c),__scc(d),__scc(e),__scc(f))
|
^
../src_musl/src/internal/syscall.h:57:27: note: in expansion of macro
‘__SYSCALL_DISP’ 57 | #define __syscall_cp(...)
__SYSCALL_DISP(__syscall_cp,__VA_ARGS__) |
^~~~~~~~~~~~~~
../src_musl/src/internal/syscall.h:62:41: note: in expansion of macro
‘__syscall_cp’ 62 | #define __socketcall_cp(nm,a,b,c,d,e,f)
__syscall_cp(SYS_##nm, a, b, c, d, e, f) |
^~~~~~~~~~~~
../src_musl/src/internal/syscall.h:47:53: note: in expansion of macro
‘__socketcall_cp’
47 | #define socketcall_cp(nm,a,b,c,d,e,f)
__syscall_ret(__socketcall_cp(nm,a,b,c,d,e,f))
|
^~~~~~~~~~~~~~~
../src_musl/src/network/accept.c:6:16: note: in expansion of macro
‘socketcall_cp’ 6 | return socketcall_cp(accept, fd, addr,
len, 0, 0, 0); | ^~~~~~~~~~~~~
../src_musl/src/network/accept.c:7:1: warning: control reaches end of
non-void function [-Wreturn-type]
7 | }
| ^
make[2]: *** [Makefile:159: obj/src/network/accept.lo] Error 1
make[2]: Leaving directory
'/usr/local/tmp/crew/musl_native_toolchain.20220216215322.dir/build/local/i686-linux-musl/obj_musl'
make[1]: *** [Makefile:249:
obj_musl/.lc_built] Error 2 make[1]:
Leaving directory
'/usr/local/tmp/crew/musl_native_toolchain.20220216215322.dir/build/local/i686-linux-musl'
make: ***
[Makefile:194: all] Error 2
On Wed, Feb 16, 2022, 4:53 PM Satadru Pramanik <satadru@...il.com> wrote:
> I was looking at that commit too. I've started a build with that reverted
> and should be able to check back on that tomorrow.
>
> On Wed, Feb 16, 2022 at 4:33 PM Rich Felker <dalias@...ifal.cx> wrote:
>
>> On Wed, Feb 16, 2022 at 01:44:35PM -0500, Satadru Pramanik wrote:
>> > The only change to socket.c I'm seeing is use __socketcall to simplify
>> > socket()
>> > <
>> https://git.musl-libc.org/cgit/musl/commit/?id=7063c459e7dbd63c2c94e04413743abab5272001
>> >,
>> > so maybe it would make sense for me to try building with that reversed?
>>
>> That should not be a functional change, but you may be overlooking
>> commit c2feda4e2ea61f4da73f2f38b2be5e327a7d1a91, which was: using the
>> new (added in 4.3) individual socket syscalls instead of the legacy
>> multiplexed SYS_socketcall. It's supposed to fall back to using the
>> old ones, but perhaps something goes wrong on your kernel that's
>> preventing it. I'm not sure what the mechanism by which it works when
>> straced/single-stepped could be, though, but if it's a weird kernel
>> bug anything is possible.
>>
>> Reverting that commit should be entirely safe, if it turns out to be
>> what's triggering your problem, but I'd like to get to the root cause
>> and see if there's anything we can do to ensure this doesn't come up
>> again.
>>
>>
>> > On Wed, Feb 16, 2022 at 1:37 PM Satadru Pramanik <satadru@...il.com>
>> wrote:
>> >
>> > >
>> > >>
>> > >> - Whether any network traffic occurs when it fails (in the real
>> > >> environment not a replicated one elsewhere).
>> > >>
>> > >>
>> > > There is no network traffic in the real environment.
>> > >
>> > >
>> > >> - Whether it fails or succeeds under strace (in the real
>> > >> environment not a replicated one elsewhere).
>> > >>
>> > >> It succeeds in strace (in the real environment)
>> > >
>> > >
>> > >
>> > >> - Whether the real environment involves Docker or not.
>> > >>
>> > >> The real environment does not involve docker.
>> > >
>> > >
>> > >
>> > >> - What's in resolv.conf (in the real environment not a replicated one
>> > >> elsewhere) and what nameserver software (if known) is running on
>> the
>> > >> nameserver(s) listed in there.
>> > >>
>> > >> The nameserver is picked up from dhcp. The contents of the file are
>> as
>> > > follows:
>> > > nameserver 192.168.0.1
>> > > search lan.
>> > > options single-request timeout:1 attempts:5
>> > >
>> > >
>> > >> - Anything else that might be relevant.
>> > >>
>> > >> DNS server is dnsmasq running on a current OpenWRT device.
>> > >
>> > >
>> > >> It's really hard to offer any productive advice when the problem is
>> > >> unclear.
>> > >>
>> > >> Apologies for the confusion.
>> > > I'm really just trying to debug this getaddrinfo breakage on this
>> older
>> > > hardware. The docker containers setup is something we use to build
>> packages
>> > > for this hardware, and our frustration is that the software works
>> perfectly
>> > > fine in the docker containers, but not on the hardware.
>> > >
>> > > > Any other suggestions on how to track down this issue?
>> > >>
>> > >> Rather than stepping through, I would put a single breakpoint at a
>> > >> place you want to see whether execution reaches before running the
>> > >> test program, then start it and see if the breakpoint fires or not.
>> > >> Then remove the breakpoint, add a different one, and repeat. For
>> > >> example, see if __res_msend is ever called, and if so, whether
>> > >> particular lines of it are reached (or just put breakpoints on some
>> of
>> > >> the functions it calls, like socket, bind, recvfrom, poll, etc. to
>> see
>> > >> if they're called).
>> > >>
>> > >> It might also be useful to put a breakpoint on clock_gettime and then
>> > >> 'finish' to see what it returns (in case the problem is something
>> > >> time64-related).
>> > >>
>> > >>
>> > > The only breakpoint which fixed the execution was for line 20 (which
>> > > invokes getaddrinfo). Stepping through the __kernel_vsyscall and then
>> > > continuing is the only way it does not result in failure.
>> > >
>> > > Any later breakpoints fail.
>> > >
>> > > I went though the other breakpoints as requested.
>> > > clock_gettime did not fire.
>> > >
>> > > Breakpoint 1 at 0x5c2f7: file
>> ../src_musl/compat/time32/clock_gettime32.c,
>> > > line 9.
>> > > __res_msend, setsockopt also did not fire.
>> > > The ones that did fire were: socket, bind, recvfrom, poll,
>> __res_msend_rc,
>> > > memset, sendto, __get_resolv_conf, pthread_setcancelstate,
>> > > __pthread_setcancelstate, __lookup_serv, __lookup_name, memcpy
>> > >
>> > > When breaking on socket, stepping through the __kernel_vsyscall call
>> after
>> > > socket and then continuing succeeds.
>> > >
>> > > Is it possible that the socket is not waiting long enough for a
>> response
>> > > from __kernel_vsyscall? Has that changed?
>> > > Breaking, stepping, and continuing on every other function above
>> fails.
>> > >
>> > > The gdb log is attached.
>> > >
>> > > Regards,
>> > >
>> > > Satadru
>> > >
>> > >
>>
>
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