From: Ammar Faizi <ammar.faizi@students.amikom.ac.id>
To: Willy Tarreau <w@1wt.eu>
Cc: Ammar Faizi <ammar.faizi@students.amikom.ac.id>,
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>,
Louvian Lyndal <louvianlyndal@gmail.com>
Subject: Re: [PATCH 2/2] tools/nolibc: x86-64: Fix startup code bug
Date: Fri, 15 Oct 2021 15:57:01 +0700 [thread overview]
Message-ID: <6sZ9qpcJvtqCksJQVaiZyA-ammarfaizi2@gnuweeb.org> (raw)
In-Reply-To: <CtypPaXXhVINRV0090UVzA-ammarfaizi2@gnuweeb.org>
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.
```
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* Bug reproducer and test for Willy's nolibc (x86-64) by Ammar.
*
* Compile with:
* gcc -O3 -ggdb3 -nostdlib -o test test.c
*/
#include "tools/include/nolibc/nolibc.h"
static void dump_argv(int argc, char *argv[])
{
int i;
const char str[] = "\nDumping argv...\n";
write(1, str, strlen(str));
for (i = 0; i < argc; i++) {
write(1, argv[i], strlen(argv[i]));
write(1, "\n", 1);
}
}
static void dump_envp(char *envp[])
{
int i = 0;
const char str[] = "\nDumping envp...\n";
write(1, str, strlen(str));
while (envp[i] != NULL) {
write(1, envp[i], strlen(envp[i]));
write(1, "\n", 1);
i++;
}
}
#define read_barrier(PTR) __asm__ volatile(""::"r"(PTR):"memory")
__attribute__((__target__("sse2")))
static void test_sse_move_aligned(void)
{
int i;
int arr[32] __attribute__((__aligned__(16)));
/*
* The assignment inside this loop is very likely
* performed with aligned move, thus if we don't
* align the %rsp properly, it will fault!
*
* If we fault due to misaligned here, then there
* must be a caller below us that violates SysV
* ABI w.r.t. to %rsp alignment before func call.
*/
for (i = 0; i < 32; i++)
arr[i] = 1;
read_barrier(arr);
}
int main(int argc, char *argv[], char *envp[])
{
dump_argv(argc, argv);
dump_envp(envp);
test_sse_move_aligned();
return 0;
}
```
--
Ammar Faizi
next prev parent reply other threads:[~2021-10-15 8:57 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 [this message]
2021-10-15 9:26 ` Bedirhan KURT
2021-10-15 9:58 ` Ammar Faizi
2021-10-15 9:41 ` Louvian Lyndal
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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