linux-kernel - Re: [PATCH] um: use POSIX ucontext

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Date:   Wed, 15 Nov 2017 12:15:00 +0100
From:   Richard Weinberger <richard@....at>
To:     Krzysztof Mazur <krzysiek@...lesie.net>
Cc:     Jeff Dike <jdike@...toit.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        user-mode-linux-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: use POSIX ucontext_t instead of struct ucontext

Am Mittwoch, 15. November 2017, 12:04:16 CET schrieb Krzysztof Mazur:
> On Wed, Nov 15, 2017 at 11:19:41AM +0100, Richard Weinberger wrote:
> > Am Mittwoch, 15. November 2017, 11:12:39 CET schrieb Krzysztof Mazur:
> > > glibc 2.26 removed the 'struct ucontext' to "improve" POSIX compliance
> > > and break programs, including User Mode Linux. Fix User Mode Linux
> > > by using POSIX ucontext_t.
> > > 
> > > This fixes:
> > > 
> > > arch/um/os-Linux/signal.c: In function 'hard_handler':
> > > arch/um/os-Linux/signal.c:163:22: error: dereferencing pointer to
> > > incomplete type 'struct ucontext' mcontext_t *mc = &uc->uc_mcontext;
> > > arch/x86/um/stub_segv.c: In function 'stub_segv_handler':
> > > arch/x86/um/stub_segv.c:16:13: error: dereferencing pointer to
> > > incomplete
> > > type 'struct ucontext' &uc->uc_mcontext);
> > 
> > Do all older glibcs have ucontext_t?
> > Otherwise this patch will break other stuff.
> 
> Yes, ucontext_t typedef was always available. They changed:
> 
> typedef struct ucontext { ... } ucontex_t;
> 
> to
> 
> typedef struct ucontext_t { ... } ucontex_t;
> 
> https://sourceware.org/glibc/wiki/Release/2.26#Removal_of_.27struct_ucontext
> .27

Okay, then we can mark your patch as stable and hope for the best. ;-)

Thanks,
//richard