On 2018-12-21 11:51, Tim Rühsen wrote:
> On 12/19/18 12:55 AM, Aurelien Jarno wrote:
> > On 2018-12-18 22:11, Aurelien Jarno wrote:
> >> On 2018-12-18 21:34, Aurelien Jarno wrote:
> >>> Hi,
> >>>
> >>> On 2018-12-18 15:15, Tim Ruehsen wrote:
> >>>> Package: libc6-armhf-cross
> >>>> Version: 2.28-2cross2
> >>>> Severity: normal
> >>>>
> >>>> Dear Maintainer,
> >>>>
> >>>> currently strerror(-3) sets errno unexpectedly to ENOMEM (12).
> >>>>
> >>>> The expected errno value would be either EINVAL or not touching errno
> >>>> at all.
> >>>>
> >>>> This behavior is relatively new and causes some CI cross builds to fail.
> >>>> The failing test is a gnulib test (test-strerror.c).
> >>>>
> >>>
> >>> I can reproduce the issue with libc6-armhf-cross 2.28-2cross2 and
> >>> qemu-arm-static 1:3.1+dfsg-1, but not with the same binary on real
> >>> hardware nor on qemu-user-static 1:2.12+dfsg-3+b1. I would therefore
> >>> think it's a qemu bug.
> >>
> >> Hmm, I am wrong, I can actually reproduce it with qemu-user-static
> >> version 1:2.12+dfsg-3+b1. But I can't reproduce it on real hardware.
> > 
> > It seems to have been caused by this upstream patch:
> > 
> > | commit 1294b1892e19d70e9e4dca0a2f3e39497f262a42
> > | Author: Wilco Dijkstra <wdijk...@arm.com>
> > | Date:   Thu Mar 15 17:57:03 2018 +0000
> > | 
> > |     Add support for sqrt asm redirects
> > |     
> > |     This patch series cleans up the many uses of  __ieee754_sqrt(f/l) in 
> > GLIBC.
> > |     The goal is to enable GCC to do the inlining, and if this fails call 
> > the
> > |     __ieee754_sqrt function.  This is done by internally declaring sqrt 
> > with asm
> > |     redirects.  The compat symbols and sqrt wrappers need to disable the 
> > redirect.
> > |     The redirect is also disabled if there are already redirects defined 
> > when
> > |     using -ffinite-math-only.
> > |     
> > |     All math functions (but not math tests, non-library code and 
> > libnldbl) are
> > |     built with -fno-math-errno which means GCC will typically inline sqrt 
> > as a
> > |     single instruction.  This means targets are no longer forced to add a 
> > special
> > |     inline for sqrt.
> > |     
> > |             * include/math.h (sqrt): Declare with asm redirect.
> > |             (sqrtf): Likewise.
> > |             (sqrtl): Likewise.
> > |             (sqrtf128): Likewise.
> > |             * Makeconfig: Add -fno-math-errno for libc/libm, but build 
> > testsuite,
> > |             nonlib and libnldbl with -fmath-errno.
> > |             * math/w_sqrt_compat.c: Define NO_MATH_REDIRECT.
> > |             * math/w_sqrt_template.c: Likewise.
> > |             * math/w_sqrtf_compat.c: Likewise.
> > |             * math/w_sqrtl_compat.c: Likewise.
> > |             * sysdeps/i386/fpu/w_sqrt.c: Likewise.
> > |             * sysdeps/i386/fpu/w_sqrt_compat.c: Likewise.
> > |             * sysdeps/generic/math-type-macros-float128.h: Remove math.h 
> > and
> > |             complex.h.
> > 
> > And more precisely by building libc with -fno-math-errno.
> 
> Thanks for looking into it.
> 
> How is the proceeding ? Is there enough info to fix (or report upstream)
> ? If not, what has to be done ?

No it's not enough to fix it or report it upstream. We still have to
understand the exact issue. For me it's not yet clear if the bug is in
QEMU or in glibc. The fact that it works fine on real hardware would
go towards a QEMU bug, but there is no proof yet.

Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurel...@aurel32.net                 http://www.aurel32.net

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