linux-kernel - Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)

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Message-ID: <87tvcsv1pk.fsf@oldenburg2.str.redhat.com>
Date:   Fri, 14 Jun 2019 13:35:51 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     carlos <carlos@...hat.com>, Joseph Myers <joseph@...esourcery.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        libc-alpha <libc-alpha@...rceware.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ben Maurer <bmaurer@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Rich Felker <dalias@...c.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>
Subject: Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)

* Mathieu Desnoyers:

> * Makefile:
>
> LIBCPATH=/home/efficios/glibc-test/lib
> KERNEL_HEADERS=/home/efficios/git/linux-percpu-dev/usr/include
> CFLAGS=-I${KERNEL_HEADERS} -L${LIBCPATH} -Wl,--rpath=${LIBCPATH} -Wl,--dynamic-linker=${LIBCPATH}/ld-linux-x86-64.so.2
>
> all:
> 	gcc ${CFLAGS} -o a a.c
> 	gcc ${CFLAGS} -shared -fPIC -o s.so s.c

For me, that does not correctly link against the built libc because the
system dynamic loader seeps into the link.

> specifically this commit:
> https://github.com/compudj/glibc-dev/commit/c49a286497d065a7fc00aafd846e6edce14f97fc

This commit links __rseq_handled into libc.so.6 via rseq-sym.c, but does
not export it from there.

Thanks,
Florian