From: Louvian Lyndal <louvianlyndal@gmail.com>
To: Ammar Faizi <ammar.faizi@students.amikom.ac.id>
Cc: Willy Tarreau <w@1wt.eu>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
David Laight <David.Laight@aculab.com>,
Peter Cordes <peter@cordes.ca>,
Bedirhan KURT <windowz414@gnuweeb.org>
Subject: Re: [PATCH 2/2] tools/nolibc: x86-64: Fix startup code bug
Date: Fri, 15 Oct 2021 16:41:20 +0700 [thread overview]
Message-ID: <CAP2ubg+p9sxJRKVhRAqYE0RKVU0Xz81YYy+=fysRiScMtAV2LQ@mail.gmail.com> (raw)
In-Reply-To: <6sZ9qpcJvtqCksJQVaiZyA-ammarfaizi2@gnuweeb.org>
On Fri, Oct 15, 2021 at 3:57 PM Ammar Faizi wrote:
>
> Hi,
>
> This is a code to test.
>
> Compile with:
> gcc -O3 -ggdb3 -nostdlib -o test test.c
>
> Technical explanation:
> The System V ABI mandates the %rsp must be 16-byte aligned before
> performing a function call, but the current nolibc.h violates it.
>
> This %rsp alignment violation makes the callee can't align its stack
> properly. Note that the callee may have a situation where it requires
> vector aligned move. For example, `movaps` with memory operand w.r.t.
> xmm registers, it requires the src/dst address be 16-byte aligned.
>
> Since the callee can't align its stack properly, it will segfault when
> executing `movaps`. The following C code is the reproducer and test
> to ensure the bug really exists and this patch fixes it.
Hello,
With the current nolibc.h, the program segfault on movaps:
Program received signal SIGSEGV, Segmentation fault.
0x0000555555555032 in dump_argv (argv=0x7fffffffe288, argc=1) at test.c:15
15 const char str[] = "\nDumping argv...\n";
(gdb) x/20i main
0x555555555000 <main>: endbr64
0x555555555004 <main+4>: push %r14
0x555555555006 <main+6>: push %r13
0x555555555008 <main+8>: mov %edi,%r13d
0x55555555500b <main+11>: push %r12
0x55555555500d <main+13>: push %rbp
0x55555555500e <main+14>: mov %rdx,%rbp
0x555555555011 <main+17>: mov $0xa,%edx
0x555555555016 <main+22>: push %rbx
0x555555555017 <main+23>: mov %rsi,%rbx
0x55555555501a <main+26>: sub $0x8,%rsp
0x55555555501e <main+30>: movdqa 0xffa(%rip),%xmm0 # 0x555555556020
0x555555555026 <main+38>: mov %dx,-0x68(%rsp)
0x55555555502b <main+43>: lea -0x78(%rsp),%r12
0x555555555030 <main+48>: xor %edx,%edx
=> 0x555555555032 <main+50>: movaps %xmm0,-0x78(%rsp)
0x555555555037 <main+55>: nopw 0x0(%rax,%rax,1)
0x555555555040 <main+64>: add $0x1,%rdx
0x555555555044 <main+68>: cmpb $0x0,(%r12,%rdx,1)
0x555555555049 <main+73>: jne 0x555555555040 <main+64>
(gdb) p $rsp-0x78
$1 = (void *) 0x7fffffffe1c8
(gdb)
Apparently it's because $rsp-0x78 is not multiple of 16. After this
patchset, it works fine. gcc version 11.1.0
Tested-by: Louvian Lyndal <louvianlyndal@gmail.com>
next prev parent reply other threads:[~2021-10-15 9:41 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-11 4:03 [PATCH] tools/nolibc: x86: Remove `r8`, `r9` and `r10` from the clobber list Ammar Faizi
2021-10-12 5:28 ` Willy Tarreau
2021-10-12 8:36 ` Ammar Faizi
2021-10-12 9:06 ` Willy Tarreau
2021-10-12 20:29 ` Borislav Petkov
2021-10-12 21:51 ` Borislav Petkov
2021-10-12 22:23 ` Ammar Faizi
2021-10-13 3:01 ` Willy Tarreau
2021-10-13 3:32 ` Ammar Faizi
2021-10-13 3:34 ` Ammar Faizi
2021-10-13 3:37 ` Ammar Faizi
2021-10-13 12:43 ` Borislav Petkov
2021-10-13 12:51 ` Willy Tarreau
2021-10-13 13:06 ` Borislav Petkov
2021-10-13 14:07 ` Willy Tarreau
2021-10-13 14:20 ` Borislav Petkov
2021-10-13 14:24 ` Willy Tarreau
2021-10-13 16:24 ` Michael Matz
2021-10-13 16:30 ` Willy Tarreau
2021-10-13 16:51 ` Andy Lutomirski
2021-10-13 16:52 ` Borislav Petkov
2021-10-14 8:44 ` Ammar Faizi
2021-10-14 12:44 ` Michael Matz
2021-10-14 14:31 ` Borislav Petkov
2021-10-19 9:06 ` David Laight
2021-10-23 20:40 ` H. Peter Anvin
2021-10-12 21:21 ` David Laight
2021-10-12 23:02 ` Subject: " Ammar Faizi
2021-10-13 9:03 ` [PATCH v2] " Ammar Faizi
2021-10-15 8:25 ` [PATCH 0/2] Fix clobber list and startup code bug Ammar Faizi
2021-10-15 8:25 ` [PATCH 1/2] tools/nolibc: x86: Remove `r8`, `r9` and `r10` from the clobber list Ammar Faizi
2021-10-18 5:52 ` Willy Tarreau
2021-10-15 8:25 ` [PATCH 2/2] tools/nolibc: x86-64: Fix startup code bug Ammar Faizi
2021-10-15 8:57 ` Ammar Faizi
2021-10-15 9:26 ` Bedirhan KURT
2021-10-15 9:58 ` Ammar Faizi
2021-10-15 9:41 ` Louvian Lyndal [this message]
2021-10-18 4:58 ` Willy Tarreau
2021-10-18 6:53 ` Ammar Faizi
2021-10-23 13:27 ` Ammar Faizi
2021-10-23 13:43 ` Willy Tarreau
2021-10-24 2:11 ` [PATCHSET v2 0/2] tools/nolibc: Fix startup code bug and small improvement Ammar Faizi
2021-10-24 2:11 ` [PATCH 1/2] tools/nolibc: x86-64: Fix startup code bug Ammar Faizi
2021-10-24 2:11 ` [PATCH 2/2] tools/nolibc: x86-64: Use `mov $60,%eax` instead of `mov $60,%rax` Ammar Faizi
2021-10-24 11:41 ` [PATCHSET v2 0/2] tools/nolibc: Fix startup code bug and small improvement Willy Tarreau
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