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elf: Fix _dl_debug_vdprintf to work before self-relocation

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The strlen might trigger and invalid GOT entry if it used before
the process is self-relocated (for instance on dl-tunables if any
error occurs).

For i386, _dl_writev with PIE requires to use the old 'int $0x80'
syscall mode because the calling the TLS register (gs) is not yet
initialized.

Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
Adhemerval Zanella 2023-11-06 17:25:40 -03:00
parent 680c597e9c
commit 434eca873f
4 changed files with 48 additions and 2 deletions
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16
elf/dl-printf.c
View File

@ -17,6 +17,10 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <string.h>
#if BUILD_PIE_DEFAULT
# pragma GCC visibility push(hidden)
#endif
#include <_itoa.h>
#include <assert.h>
#include <dl-writev.h>
@ -25,11 +29,19 @@
#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/uio.h>
#include <unistd.h>
#include <intprops.h>
/* The function might be called before the process is self-relocated. */
static size_t
_dl_debug_strlen (const char *s)
{
const char *p = s;
for (; *s != '\0'; s++);
return s - p;
}
/* Bare-bones printf implementation. This function only knows about
the formats and flags needed and can handle only up to 64 stripes in
the output. */
@ -193,7 +205,7 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
case 's':
/* Get the string argument. */
iov[niov].iov_base = va_arg (arg, char *);
iov[niov].iov_len = strlen (iov[niov].iov_base);
iov[niov].iov_len = _dl_debug_strlen (iov[niov].iov_base);
if (prec != -1)
iov[niov].iov_len = MIN ((size_t) prec, iov[niov].iov_len);
++niov;

5
stdio-common/Makefile
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@ -460,6 +460,11 @@ CFLAGS-isoc23_scanf.c += -fexceptions
CFLAGS-dprintf.c += $(config-cflags-wno-ignored-attributes)
# Called during static library initialization, so turn stack-protection
# off for non-shared builds.
CFLAGS-_itoa.o = $(no-stack-protector)
CFLAGS-_itoa.op = $(no-stack-protector)
# scanf18.c and scanf19.c test a deprecated extension which is no
# longer visible under most conformance levels; see the source files
# for more detail.

5
stdio-common/_itoa.c
View File

@ -16,6 +16,11 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* Mark symbols hidden in static PIE for early self relocation to work.
Note: string.h may have ifuncs which cannot be hidden on i686. */
#if BUILD_PIE_DEFAULT
# pragma GCC visibility push(hidden)
#endif
#include <gmp-mparam.h>
#include <gmp.h>
#include <limits.h>

24
sysdeps/unix/sysv/linux/i386/dl-writev.h Normal file
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@ -0,0 +1,24 @@
/* Message-writing for the dynamic linker. Linux/i386 version.
Copyright (C) 2013-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#if BUILD_PIE_DEFAULT
/* Can't use "call *%gs:SYSINFO_OFFSET" during startup in static PIE. */
# define I386_USE_SYSENTER 0
#endif
#include <sysdeps/unix/sysv/linux/dl-writev.h>