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From: Adhemerval Zanella <azanella@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] elf: Fix _dl_debug_vdprintf to work before self-relocation Date: Tue, 21 Nov 2023 20:49:01 +0000 (GMT) [thread overview] Message-ID: <20231121204901.F0E2E3858C54@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=434eca873f14f618d6c2279b54fb809fb56f2c50 commit 434eca873f14f618d6c2279b54fb809fb56f2c50 Author: Adhemerval Zanella <adhemerval.zanella@linaro.org> Date: Mon Nov 6 17:25:40 2023 -0300 elf: Fix _dl_debug_vdprintf to work before self-relocation 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> Diff: --- elf/dl-printf.c | 16 ++++++++++++++-- stdio-common/Makefile | 5 +++++ stdio-common/_itoa.c | 5 +++++ sysdeps/unix/sysv/linux/i386/dl-writev.h | 24 ++++++++++++++++++++++++ 4 files changed, 48 insertions(+), 2 deletions(-) diff --git a/elf/dl-printf.c b/elf/dl-printf.c index 6efb4c019a..5e93208535 100644 --- a/elf/dl-printf.c +++ b/elf/dl-printf.c @@ -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; diff --git a/stdio-common/Makefile b/stdio-common/Makefile index bacb795fed..e88a9cea29 100644 --- a/stdio-common/Makefile +++ b/stdio-common/Makefile @@ -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. diff --git a/stdio-common/_itoa.c b/stdio-common/_itoa.c index 3037b0f529..48f2903ecb 100644 --- a/stdio-common/_itoa.c +++ b/stdio-common/_itoa.c @@ -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> diff --git a/sysdeps/unix/sysv/linux/i386/dl-writev.h b/sysdeps/unix/sysv/linux/i386/dl-writev.h new file mode 100644 index 0000000000..624d0e46b0 --- /dev/null +++ b/sysdeps/unix/sysv/linux/i386/dl-writev.h @@ -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>
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