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Static PIE extends address space layout randomization to static executables. It provides additional security hardening benefits at the cost of some memory and performance. Dynamic linker, ld.so, is a standalone program which can be loaded at any address. This patch adds a configure option, --enable-static-pie, to embed the part of ld.so in static executable to create static position independent executable (static PIE). A static PIE is similar to static executable, but can be loaded at any address without help from a dynamic linker. When --enable-static-pie is used to configure glibc, libc.a is built as PIE and all static executables, including tests, are built as static PIE. The resulting libc.a can be used together with GCC 8 or above to build static PIE with the compiler option, -static-pie. But GCC 8 isn't required to build glibc with --enable-static-pie. Only GCC with PIE support is needed. When an older GCC is used to build glibc with --enable-static-pie, proper input files are passed to linker to create static executables as static PIE, together with "-z text" to prevent dynamic relocations in read-only segments, which are not allowed in static PIE. The following changes are made for static PIE: 1. Add a new function, _dl_relocate_static_pie, to: a. Get the run-time load address. b. Read the dynamic section. c. Perform dynamic relocations. Dynamic linker also performs these steps. But static PIE doesn't load any shared objects. 2. Call _dl_relocate_static_pie at entrance of LIBC_START_MAIN in libc.a. crt1.o, which is used to create dynamic and non-PIE static executables, is updated to include a dummy _dl_relocate_static_pie. rcrt1.o is added to create static PIE, which will link in the real _dl_relocate_static_pie. grcrt1.o is also added to create static PIE with -pg. GCC 8 has been updated to support rcrt1.o and grcrt1.o for static PIE. Static PIE can work on all architectures which support PIE, provided: 1. Target must support accessing of local functions without dynamic relocations, which is needed in start.S to call __libc_start_main with function addresses of __libc_csu_init, __libc_csu_fini and main. All functions in static PIE are local functions. If PIE start.S can't reach main () defined in a shared object, the code sequence: pass address of local_main to __libc_start_main ... local_main: tail call to main via PLT can be used. 2. start.S is updated to check PIC instead SHARED for PIC code path and avoid dynamic relocation, when PIC is defined and SHARED isn't defined, to support static PIE. 3. All assembly codes are updated check PIC instead SHARED for PIC code path to avoid dynamic relocations in read-only sections. 4. All assembly codes are updated check SHARED instead PIC for static symbol name. 5. elf_machine_load_address in dl-machine.h are updated to support static PIE. 6. __brk works without TLS nor dynamic relocations in read-only section so that it can be used by __libc_setup_tls to initializes TLS in static PIE. NB: When glibc is built with GCC defaulted to PIE, libc.a is compiled with -fPIE, regardless if --enable-static-pie is used to configure glibc. When glibc is configured with --enable-static-pie, libc.a is compiled with -fPIE, regardless whether GCC defaults to PIE or not. The same libc.a can be used to build both static executable and static PIE. There is no need for separate PIE copy of libc.a. On x86-64, the normal static sln: text data bss dec hex filename 625425 8284 5456 639165 9c0bd elf/sln the static PIE sln: text data bss dec hex filename 657626 20636 5392 683654 a6e86 elf/sln The code size is increased by 5% and the binary size is increased by 7%. Linker requirements to build glibc with --enable-static-pie: 1. Linker supports --no-dynamic-linker to remove PT_INTERP segment from static PIE. 2. Linker can create working static PIE. The x86-64 linker needs the fix for https://sourceware.org/bugzilla/show_bug.cgi?id=21782 The i386 linker needs to be able to convert "movl main@GOT(%ebx), %eax" to "leal main@GOTOFF(%ebx), %eax" if main is defined locally. Binutils 2.29 or above are OK for i686 and x86-64. But linker status for other targets need to be verified. 3. Linker should resolve undefined weak symbols to 0 in static PIE: https://sourceware.org/bugzilla/show_bug.cgi?id=22269 4. Many ELF backend linkers incorrectly check bfd_link_pic for TLS relocations, which should check bfd_link_executable instead: https://sourceware.org/bugzilla/show_bug.cgi?id=22263 Tested on aarch64, i686 and x86-64. Using GCC 7 and binutils master branch, build-many-glibcs.py with --enable-static-pie with all patches for static PIE applied have the following build successes: PASS: glibcs-aarch64_be-linux-gnu build PASS: glibcs-aarch64-linux-gnu build PASS: glibcs-armeb-linux-gnueabi-be8 build PASS: glibcs-armeb-linux-gnueabi build PASS: glibcs-armeb-linux-gnueabihf-be8 build PASS: glibcs-armeb-linux-gnueabihf build PASS: glibcs-arm-linux-gnueabi build PASS: glibcs-arm-linux-gnueabihf build PASS: glibcs-arm-linux-gnueabihf-v7a build PASS: glibcs-arm-linux-gnueabihf-v7a-disable-multi-arch build PASS: glibcs-m68k-linux-gnu build PASS: glibcs-microblazeel-linux-gnu build PASS: glibcs-microblaze-linux-gnu build PASS: glibcs-mips64el-linux-gnu-n32 build PASS: glibcs-mips64el-linux-gnu-n32-nan2008 build PASS: glibcs-mips64el-linux-gnu-n32-nan2008-soft build PASS: glibcs-mips64el-linux-gnu-n32-soft build PASS: glibcs-mips64el-linux-gnu-n64 build PASS: glibcs-mips64el-linux-gnu-n64-nan2008 build PASS: glibcs-mips64el-linux-gnu-n64-nan2008-soft build PASS: glibcs-mips64el-linux-gnu-n64-soft build PASS: glibcs-mips64-linux-gnu-n32 build PASS: glibcs-mips64-linux-gnu-n32-nan2008 build PASS: glibcs-mips64-linux-gnu-n32-nan2008-soft build PASS: glibcs-mips64-linux-gnu-n32-soft build PASS: glibcs-mips64-linux-gnu-n64 build PASS: glibcs-mips64-linux-gnu-n64-nan2008 build PASS: glibcs-mips64-linux-gnu-n64-nan2008-soft build PASS: glibcs-mips64-linux-gnu-n64-soft build PASS: glibcs-mipsel-linux-gnu build PASS: glibcs-mipsel-linux-gnu-nan2008 build PASS: glibcs-mipsel-linux-gnu-nan2008-soft build PASS: glibcs-mipsel-linux-gnu-soft build PASS: glibcs-mips-linux-gnu build PASS: glibcs-mips-linux-gnu-nan2008 build PASS: glibcs-mips-linux-gnu-nan2008-soft build PASS: glibcs-mips-linux-gnu-soft build PASS: glibcs-nios2-linux-gnu build PASS: glibcs-powerpc64le-linux-gnu build PASS: glibcs-powerpc64-linux-gnu build PASS: glibcs-tilegxbe-linux-gnu-32 build PASS: glibcs-tilegxbe-linux-gnu build PASS: glibcs-tilegx-linux-gnu-32 build PASS: glibcs-tilegx-linux-gnu build PASS: glibcs-tilepro-linux-gnu build and the following build failures: FAIL: glibcs-alpha-linux-gnu build elf/sln is failed to link due to: assertion fail bfd/elf64-alpha.c:4125 This is caused by linker bug and/or non-PIC code in PIE libc.a. FAIL: glibcs-hppa-linux-gnu build elf/sln is failed to link due to: collect2: fatal error: ld terminated with signal 11 [Segmentation fault] https://sourceware.org/bugzilla/show_bug.cgi?id=22537 FAIL: glibcs-ia64-linux-gnu build elf/sln is failed to link due to: collect2: fatal error: ld terminated with signal 11 [Segmentation fault] FAIL: glibcs-powerpc-linux-gnu build FAIL: glibcs-powerpc-linux-gnu-soft build FAIL: glibcs-powerpc-linux-gnuspe build FAIL: glibcs-powerpc-linux-gnuspe-e500v1 build elf/sln is failed to link due to: ld: read-only segment has dynamic relocations. This is caused by linker bug and/or non-PIC code in PIE libc.a. See: https://sourceware.org/bugzilla/show_bug.cgi?id=22264 FAIL: glibcs-powerpc-linux-gnu-power4 build elf/sln is failed to link due to: findlocale.c:96:(.text+0x22c): @local call to ifunc memchr This is caused by linker bug and/or non-PIC code in PIE libc.a. FAIL: glibcs-s390-linux-gnu build elf/sln is failed to link due to: collect2: fatal error: ld terminated with signal 11 [Segmentation fault], core dumped assertion fail bfd/elflink.c:14299 This is caused by linker bug and/or non-PIC code in PIE libc.a. FAIL: glibcs-sh3eb-linux-gnu build FAIL: glibcs-sh3-linux-gnu build FAIL: glibcs-sh4eb-linux-gnu build FAIL: glibcs-sh4eb-linux-gnu-soft build FAIL: glibcs-sh4-linux-gnu build FAIL: glibcs-sh4-linux-gnu-soft build elf/sln is failed to link due to: ld: read-only segment has dynamic relocations. This is caused by linker bug and/or non-PIC code in PIE libc.a. See: https://sourceware.org/bugzilla/show_bug.cgi?id=22263 Also TLS code sequence in SH assembly syscalls in glibc doesn't match TLS code sequence expected by ld: https://sourceware.org/bugzilla/show_bug.cgi?id=22270 FAIL: glibcs-sparc64-linux-gnu build FAIL: glibcs-sparcv9-linux-gnu build FAIL: glibcs-tilegxbe-linux-gnu build FAIL: glibcs-tilegxbe-linux-gnu-32 build FAIL: glibcs-tilegx-linux-gnu build FAIL: glibcs-tilegx-linux-gnu-32 build FAIL: glibcs-tilepro-linux-gnu build elf/sln is failed to link due to: ld: read-only segment has dynamic relocations. This is caused by linker bug and/or non-PIC code in PIE libc.a. See: https://sourceware.org/bugzilla/show_bug.cgi?id=22263 [BZ #19574] * INSTALL: Regenerated. * Makeconfig (real-static-start-installed-name): New. (pic-default): Updated for --enable-static-pie. (pie-default): New for --enable-static-pie. (default-pie-ldflag): Likewise. (+link-static-before-libc): Replace $(DEFAULT-LDFLAGS-$(@F)) with $(if $($(@F)-no-pie),$(no-pie-ldflag),$(default-pie-ldflag)). Replace $(static-start-installed-name) with $(real-static-start-installed-name). (+prectorT): Updated for --enable-static-pie. (+postctorT): Likewise. (CFLAGS-.o): Add $(pie-default). (CFLAGS-.op): Likewise. * NEWS: Mention --enable-static-pie. * config.h.in (ENABLE_STATIC_PIE): New. * configure.ac (--enable-static-pie): New configure option. (have-no-dynamic-linker): New LIBC_CONFIG_VAR. (have-static-pie): Likewise. Enable static PIE if linker supports --no-dynamic-linker. (ENABLE_STATIC_PIE): New AC_DEFINE. (enable-static-pie): New LIBC_CONFIG_VAR. * configure: Regenerated. * csu/Makefile (omit-deps): Add r$(start-installed-name) and gr$(start-installed-name) for --enable-static-pie. (extra-objs): Likewise. (install-lib): Likewise. (extra-objs): Add static-reloc.o and static-reloc.os ($(objpfx)$(start-installed-name)): Also depend on $(objpfx)static-reloc.o. ($(objpfx)r$(start-installed-name)): New. ($(objpfx)g$(start-installed-name)): Also depend on $(objpfx)static-reloc.os. ($(objpfx)gr$(start-installed-name)): New. * csu/libc-start.c (LIBC_START_MAIN): Call _dl_relocate_static_pie in libc.a. * csu/libc-tls.c (__libc_setup_tls): Add main_map->l_addr to initimage. * csu/static-reloc.c: New file. * elf/Makefile (routines): Add dl-reloc-static-pie. (elide-routines.os): Likewise. (DEFAULT-LDFLAGS-tst-tls1-static-non-pie): Removed. (tst-tls1-static-non-pie-no-pie): New. * elf/dl-reloc-static-pie.c: New file. * elf/dl-support.c (_dl_get_dl_main_map): New function. * elf/dynamic-link.h (ELF_DURING_STARTUP): Also check STATIC_PIE_BOOTSTRAP. * elf/get-dynamic-info.h (elf_get_dynamic_info): Likewise. * gmon/Makefile (tests): Add tst-gmon-static-pie. (tests-static): Likewise. (DEFAULT-LDFLAGS-tst-gmon-static): Removed. (tst-gmon-static-no-pie): New. (CFLAGS-tst-gmon-static-pie.c): Likewise. (CRT-tst-gmon-static-pie): Likewise. (tst-gmon-static-pie-ENV): Likewise. (tests-special): Likewise. ($(objpfx)tst-gmon-static-pie.out): Likewise. (clean-tst-gmon-static-pie-data): Likewise. ($(objpfx)tst-gmon-static-pie-gprof.out): Likewise. * gmon/tst-gmon-static-pie.c: New file. * manual/install.texi: Document --enable-static-pie. * sysdeps/generic/ldsodefs.h (_dl_relocate_static_pie): New. (_dl_get_dl_main_map): Likewise. * sysdeps/i386/configure.ac: Check if linker supports static PIE. * sysdeps/x86_64/configure.ac: Likewise. * sysdeps/i386/configure: Regenerated. * sysdeps/x86_64/configure: Likewise. * sysdeps/mips/Makefile (ASFLAGS-.o): Add $(pie-default). (ASFLAGS-.op): Likewise. |
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