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Lu" Date: Sun, 27 Oct 2024 06:29:02 +0800 Message-ID: Subject: [PATCH v7] elf: Handle static PIE with non-zero load address [BZ #31799] To: Noah Goldstein Cc: GNU C Library , "Carlos O'Donell" , Florian Weimer X-Spam-Status: No, score=-3017.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org For a static PIE with non-zero load address, its PT_DYNAMIC segment entries contain the relocated values for the load address in static PIE. Since static PIE usually doesn't have PT_PHDR segment, use p_vaddr of the PT_LOAD segment with offset == 0 as the load address in static PIE and adjust the entries of PT_DYNAMIC segment in static PIE by properly setting the l_addr field for static PIE. This fixes BZ #31799. OK to install? Thanks. From 7b4be3b7d2667b4dca3516311167788ddf78f580 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Sun, 26 May 2024 04:55:32 -0700 Subject: [PATCH v7] elf: Handle static PIE with non-zero load address [BZ #31799] For a static PIE with non-zero load address, its PT_DYNAMIC segment entries contain the relocated values for the load address in static PIE. Since static PIE usually doesn't have PT_PHDR segment, use p_vaddr of the PT_LOAD segment with offset == 0 as the load address in static PIE and adjust the entries of PT_DYNAMIC segment in static PIE by properly setting the l_addr field for static PIE. This fixes BZ #31799. Signed-off-by: H.J. Lu --- configure | 74 ++++++++++++++++++++++++++++++++++++ configure.ac | 36 ++++++++++++++++++ elf/Makefile | 20 ++++++++++ elf/dl-reloc-static-pie.c | 30 +++++++++++---- elf/tst-pie-address-static.c | 19 +++++++++ elf/tst-pie-address.c | 28 ++++++++++++++ 6 files changed, 200 insertions(+), 7 deletions(-) create mode 100644 elf/tst-pie-address-static.c create mode 100644 elf/tst-pie-address.c diff --git a/configure b/configure index 9c0c0dce03..9bcf62dca5 100755 --- a/configure +++ b/configure @@ -8107,6 +8107,80 @@ printf "%s\n" "$libc_cv_cc_pie_default" >&6; } config_vars="$config_vars cc-pie-default = $libc_cv_cc_pie_default" +# Get Position Dependent Executable (PDE) load address to be used to +# load static Position Independent Executable (PIE) at a known working +# non-zero load address. This is only used by glibc tests to verify +# that PIE and static PIE with non-zero load address work correctly. +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking PDE load address" >&5 +printf %s "checking PDE load address... " >&6; } +if test ${libc_cv_pde_load_address+y} +then : + printf %s "(cached) " >&6 +else case e in #( + e) cat > conftest.S <&5 2>&5; then + # Get the load address of the first PT_LOAD segment. + libc_cv_pde_load_address=$(LC_ALL=C $READELF -Wl conftest \ + | $AWK '/LOAD/ { print $3; exit 0; }') +else + as_fn_error $? "${CC-cc} can not create PDE" "$LINENO" 5 +fi +rm -f conftest* ;; +esac +fi +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_pde_load_address" >&5 +printf "%s\n" "$libc_cv_pde_load_address" >&6; } +config_vars="$config_vars +pde-load-address = $libc_cv_pde_load_address" + +# Get the linker command-line option to load executable at a non-zero +# load address. This is only used by glibc tests to verify that PIE and +# static PIE with non-zero load address work correctly. +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for linker that supports -Ttext-segment=$libc_cv_pde_load_address" >&5 +printf %s "checking for linker that supports -Ttext-segment=$libc_cv_pde_load_address... " >&6; } +libc_linker_feature=no +cat > conftest.c <&5 + (eval $ac_try) 2>&5 + ac_status=$? + printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5 + test $ac_status = 0; }; } +then + if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-Ttext-segment=$libc_cv_pde_load_address -nostdlib \ + -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \ + | grep "warning: -Ttext-segment=$libc_cv_pde_load_address ignored" > /dev/null 2>&1; then + true + else + libc_linker_feature=yes + fi +fi +rm -f conftest* +if test $libc_linker_feature = yes; then + libc_cv_load_address_ldflag=-Wl,-Ttext-segment +else + libc_cv_load_address_ldflag= +fi +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5 +printf "%s\n" "$libc_linker_feature" >&6; } +config_vars="$config_vars +load-address-ldflag = $libc_cv_load_address_ldflag" + { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if we can build programs as PIE" >&5 printf %s "checking if we can build programs as PIE... " >&6; } cat confdefs.h - <<_ACEOF >conftest.$ac_ext diff --git a/configure.ac b/configure.ac index d5a00461ff..895bd5267d 100644 --- a/configure.ac +++ b/configure.ac @@ -1763,6 +1763,42 @@ fi rm -f conftest.*]) LIBC_CONFIG_VAR([cc-pie-default], [$libc_cv_cc_pie_default]) +# Get Position Dependent Executable (PDE) load address to be used to +# load static Position Independent Executable (PIE) at a known working +# non-zero load address. This is only used by glibc tests to verify +# that PIE and static PIE with non-zero load address work correctly. +AC_CACHE_CHECK([PDE load address], + libc_cv_pde_load_address, [dnl +cat > conftest.S <&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD; then + # Get the load address of the first PT_LOAD segment. + libc_cv_pde_load_address=$(LC_ALL=C $READELF -Wl conftest \ + | $AWK '/LOAD/ { print $3; exit 0; }') +else + AC_MSG_ERROR([${CC-cc} can not create PDE]) +fi +rm -f conftest*]) +LIBC_CONFIG_VAR([pde-load-address], [$libc_cv_pde_load_address]) + +# Get the linker command-line option to load executable at a non-zero +# load address. This is only used by glibc tests to verify that PIE and +# static PIE with non-zero load address work correctly. +LIBC_LINKER_FEATURE([-Ttext-segment=$libc_cv_pde_load_address], + [-Wl,-Ttext-segment=$libc_cv_pde_load_address], + [libc_cv_load_address_ldflag=-Wl,-Ttext-segment], + [libc_cv_load_address_ldflag=]) +LIBC_CONFIG_VAR([load-address-ldflag], [$libc_cv_load_address_ldflag]) + AC_MSG_CHECKING(if we can build programs as PIE) AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#ifdef PIE_UNSUPPORTED # error PIE is not supported diff --git a/elf/Makefile b/elf/Makefile index 9cfe738919..4eaca7af67 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -1091,6 +1091,25 @@ tests-pie += \ tst-pie1 \ tst-pie2 \ # tests-pie +ifneq (,$(load-address-ldflag)) +tests += \ + tst-pie-address \ + # tests +tests-pie += \ + tst-pie-address \ + # tests-pie +LDFLAGS-tst-pie-address += $(load-address-ldflag)=$(pde-load-address) +ifeq (yes,$(enable-static-pie)) +tests += \ + tst-pie-address-static \ + # tests +tests-static += \ + tst-pie-address-static \ + # tests-static +LDFLAGS-tst-pie-address-static += \ + $(load-address-ldflag)=$(pde-load-address) +endif +endif ifeq (yes,$(have-protected-data)) tests += vismain tests-pie += vismain @@ -1937,6 +1956,7 @@ $(objpfx)tst-array5-static-cmp.out: tst-array5-static.exp \ CFLAGS-tst-pie1.c += $(pie-ccflag) CFLAGS-tst-pie2.c += $(pie-ccflag) +CFLAGS-tst-pie-address.c += $(pie-ccflag) $(objpfx)tst-piemod1.so: $(libsupport) $(objpfx)tst-pie1: $(objpfx)tst-piemod1.so diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c index 10c23d0bf0..bfee89dfc3 100644 --- a/elf/dl-reloc-static-pie.c +++ b/elf/dl-reloc-static-pie.c @@ -37,21 +37,37 @@ _dl_relocate_static_pie (void) { struct link_map *main_map = _dl_get_dl_main_map (); - /* Figure out the run-time load address of static PIE. */ - main_map->l_addr = elf_machine_load_address (); - - /* Read our own dynamic section and fill in the info array. */ - main_map->l_ld = ((void *) main_map->l_addr + elf_machine_dynamic ()); - + /* NB: elf_machine_load_address () returns the run-time load address + of static PIE. The l_addr field contains the difference between the + link-time load address in the ELF file and the run-time load address + in memory. We must subtract the link-time load address of static PIE, + which can be non-zero, when computing the l_addr field. Since static + PIE usually doesn't have PT_PHDR segment, use p_vaddr of the PT_LOAD + segment with offset == 0 as the load address of static PIE. */ + ElfW(Addr) file_p_vaddr = 0; const ElfW(Phdr) *ph, *phdr = GL(dl_phdr); size_t phnum = GL(dl_phnum); for (ph = phdr; ph < &phdr[phnum]; ++ph) - if (ph->p_type == PT_DYNAMIC) + switch (ph->p_type) { + case PT_LOAD: + if (ph->p_offset == 0) + file_p_vaddr = ph->p_vaddr; + break; + case PT_DYNAMIC: main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0; break; + default: + break; } + /* Figure out the run-time load address of static PIE. */ + ElfW(Addr) l_addr = elf_machine_load_address (); + main_map->l_addr = l_addr - file_p_vaddr; + + /* Read our own dynamic section and fill in the info array. */ + main_map->l_ld = ((void *) l_addr + elf_machine_dynamic ()); + elf_get_dynamic_info (main_map, false, true); # ifdef ELF_MACHINE_BEFORE_RTLD_RELOC diff --git a/elf/tst-pie-address-static.c b/elf/tst-pie-address-static.c new file mode 100644 index 0000000000..be2831e9d6 --- /dev/null +++ b/elf/tst-pie-address-static.c @@ -0,0 +1,19 @@ +/* Test static PIE with non-zero load address. + Copyright (C) 2024 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 + . */ + +#include "tst-pie-address.c" diff --git a/elf/tst-pie-address.c b/elf/tst-pie-address.c new file mode 100644 index 0000000000..aa1ca0a9fd --- /dev/null +++ b/elf/tst-pie-address.c @@ -0,0 +1,28 @@ +/* Test PIE with non-zero load address. + Copyright (C) 2024 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 + . */ + +#include + +static int +do_test (void) +{ + printf ("Hello\n"); + return 0; +} + +#include -- 2.47.0