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[222.152.172.8]) by smtp.gmail.com with ESMTPSA id f25-20020aa782d9000000b0063a1e7d7439sm4803334pfn.69.2023.04.22.11.24.57 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 22 Apr 2023 11:25:00 -0700 (PDT) Subject: Re: reliable reproducer, was Re: core dump analysis To: Andreas Schwab References: <4a9c1d0d-07aa-792e-921f-237d5a30fc44.ref@yahoo.com> <54597ab3-2776-2a55-9952-3bfbbc329829@linux-m68k.org> <406cb339-0a0c-4d71-9b5c-c11568793c14@gmail.com> <71af7b52-a1d4-581c-d5af-afce6991c48d@gmail.com> <7ea095ba-7df1-1ffe-e87d-12d46ebe72f6@gmail.com> <2fdc2819-526a-756f-19d0-ac1147f85b63@linux-m68k.org> <868b5214-fa13-dcf7-a671-9843169eea06@gmail.com> <87fs8sz6e9.fsf@igel.home> <878rekz0md.fsf@igel.home> Cc: Finn Thain , debian-68k@lists.debian.org, linux-m68k@lists.linux-m68k.org From: Michael Schmitz Message-ID: Date: Sun, 23 Apr 2023 06:24:55 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: <878rekz0md.fsf@igel.home> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Andreas, Am 22.04.2023 um 22:12 schrieb Andreas Schwab: > On Apr 22 2023, Michael Schmitz wrote: > >> This is the definition from the kernel's >> include/uapi/asm-generic/ucontext.h: > > That's not actually used by m68k, it uses > arch/m68k/include/asm/ucontext.h, which confusingly isn't an uapi > header. Argh - not sure how I missed that one. >> And this is /usr/include/sys/ucontext.h: >> >> /* Userlevel context. */ >> typedef struct ucontext >> { >> unsigned long int uc_flags; >> struct ucontext *uc_link; >> __sigset_t uc_sigmask; >> stack_t uc_stack; >> mcontext_t uc_mcontext; >> long int uc_filler[174]; >> } ucontext_t; >> >> uc_sigmask appears before uc_stack and uc_mcontext. > > Yes, that got fixed as part of commit 9c986f878a back in 2006. With the header corrected as per arch/m68k/include/asm/ucontext.h, I get the correct information in uc_filler[54] aka fmtvec now. Good. Every sigreturn possibly overwrites the user stack now (if the filler is used in full). Not so good. >> I'm assuming libc just passes on what the kernel set, without reordering? > > Trying to rewrite the signal context would be prohibitive, yes. Now I wonder who adds sigmask ... and whether that's also ending up on the user stack. Cheers, Michael >