From 434eca873f14f618d6c2279b54fb809fb56f2c50 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Mon, 6 Nov 2023 17:25:40 -0300 Subject: [PATCH] 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. Reference:https://sourceware.org/git/?p=glibc.git;a=commit;h=434eca873f14f618d6c2279b54fb809fb56f2c50 Checked on x86_64-linux-gnu. Reviewed-by: Siddhesh Poyarekar --- elf/dl-misc.c | 15 +++++++++++++-- stdio-common/Makefile | 5 +++++ stdio-common/_itoa.c | 5 +++++ sysdeps/unix/sysv/linux/i386/dl-writev.h | 24 ++++++++++++++++++++++++ 4 files changed, 47 insertions(+), 2 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/i386/dl-writev.h diff --git a/elf/dl-misc.c b/elf/dl-misc.c index bba2e714..5b637c7e 100644 --- a/elf/dl-misc.c +++ b/elf/dl-misc.c @@ -16,6 +16,10 @@ License along with the GNU C Library; if not, see . */ +#include +#if BUILD_PIE_DEFAULT +# pragma GCC visibility push(hidden) +#endif #include #include #include @@ -23,7 +27,6 @@ #include #include #include -#include #include #include #include @@ -71,6 +74,14 @@ _dl_sysdep_read_whole_file (const char *file, size_t *sizep, int prot) return result; } +/* 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 @@ -235,7 +246,7 @@ _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 803f16da..f9763c27 100644 --- a/stdio-common/Makefile +++ b/stdio-common/Makefile @@ -181,6 +181,11 @@ CFLAGS-isoc99_scanf.c += -fexceptions CFLAGS-errlist.c += $(fno-unit-at-a-time) CFLAGS-siglist.c += $(fno-unit-at-a-time) +# 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) + # scanf14a.c and scanf16a.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 c37d1c35..20c2e384 100644 --- a/stdio-common/_itoa.c +++ b/stdio-common/_itoa.c @@ -18,6 +18,11 @@ License along with the GNU C Library; if not, see . */ +/* 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 #include #include 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 00000000..624d0e46 --- /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 + . */ + +#if BUILD_PIE_DEFAULT +/* Can't use "call *%gs:SYSINFO_OFFSET" during startup in static PIE. */ +# define I386_USE_SYSENTER 0 +#endif + +#include -- 2.33.0