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From:   Zhouyi Zhou <zhouzhouyi@gmail.com>
Date:   Tue, 25 Apr 2023 14:01:58 +0800
Message-ID: <CAABZP2zr=jypD7w_o18o95QEj1nkFugLcNH5sbuSAY-caBQoeQ@mail.gmail.com>
Subject: Re: BUG : PowerPC RCU: torture test failed with __stack_chk_fail
To:     Michael Ellerman <mpe@ellerman.id.au>
Cc:     linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        rcu <rcu@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>, lance@osuosl.org,
        "Paul E. McKenney" <paulmck@kernel.org>
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hi

On Tue, Apr 25, 2023 at 6:07=E2=80=AFAM Michael Ellerman <mpe@ellerman.id.a=
u> wrote:
>
> Zhouyi Zhou <zhouzhouyi@gmail.com> writes:
> > Dear PowerPC and RCU developers:
> > During the RCU torture test on mainline (on the VM of Opensource Lab
> > of Oregon State University), SRCU-P failed with __stack_chk_fail:
> ...
> > by debugging, I see the r10 is assigned with r13 on c000000000226eb4,
> > but if there is a context-switch before c000000000226edc, a false
> > positive will be reported.
> >
> > [1] http://154.220.3.115/logs/0422/configformainline.txt
>
> Says:
>
> CONFIG_CC_VERSION_TEXT=3D"powerpc64le-linux-gnu-gcc-10 (Ubuntu 10.4.0-4ub=
untu1~22.04) 10.4.0"
>
> Do you see the same issue with a newer GCC?
On PPC vm of Oregon State University (I can grant rsa-pub key ssh
access if you are interested), I
build and install the gcc from git, then use the newly built gcc to
compile the kernel, the bug disappears,
I don't know why. Following is what is do:

1) git clone git://gcc.gnu.org/git/gcc.git
git rev-parse --short HEAD
f0eabc52c9a
2) mkdir gcc/build
3) cd gcc/build
4) ../configure --disable-bootstrap --prefix=3D/home/ubuntu/gcc-install
5) make -j 4 //my VM has limited memory ;-)
6) make install
7) cd  linux-dir
git rev-parse --short HEAD
61d325dcbc05
8) export PATH=3D/home/ubuntu/gcc-install/bin:$PATH
9) make vmlinux -j 8
10) ./whilebash.sh [1]

From the assembly code of srcu_gp_start_if_needed [2], I found stack protec=
tor
is operated directly on r13:

c000000000225098: 30 00 0d e9 ld      r8,48(r13)
c00000000022509c: 08 00 3c e9 ld      r9,8(r28)
c0000000002250a0: 14 42 29 7d add     r9,r9,r8
c0000000002250a4: ac 04 00 7c hwsync
c0000000002250a8: 10 00 7b 3b addi    r27,r27,16
c0000000002250ac: 14 da 29 7d add     r9,r9,r27
c0000000002250b0: a8 48 00 7d ldarx   r8,0,r9
c0000000002250b4: 01 00 08 31 addic   r8,r8,1
c0000000002250b8: ad 49 00 7d stdcx.  r8,0,r9
c0000000002250bc: f4 ff c2 40 bne-    c0000000002250b0
<srcu_gp_start_if_needed+0x220>
c0000000002250c0: 28 00 01 e9 ld      r8,40(r1)
c0000000002250c4: 78 0c 2d e9 ld      r9,3192(r13)
c0000000002250c8: 79 4a 08 7d xor.    r8,r8,r9
c0000000002250cc: 00 00 20 39 li      r9,0
c0000000002250d0: 90 03 82 40 bne     c000000000225460
<srcu_gp_start_if_needed+0x5d0>

console.log is attached at [3].

[1] 140.211.169.189/0425/whilebash.sh
[2] http://140.211.169.189/0425/srcu_gp_start_if_needed.txt
[3] http://140.211.169.189/0425/console.log

I am very glad to cooperate if there is anything else I can do ;-)

Cheers
Zhouyi
>
> There's 12.2.0 here:
>   https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/12=
.2.0/
>   https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/ppc64le/1=
2.2.0/
>
> Or if you can build in a Fedora 38 system or container, it has GCC 13.
>
> cheers