S390: Enable static PIE

System Internals / glibc - Stefan Liebler [linux.ibm.com] - 18 May 2022 12:31 UTC

This commit enables static PIE on 64bit. On 31bit, static PIE is not supported.

A new configure check in sysdeps/s390/s390-64/configure.ac also performs a minimal test for requirements in ld: Ensure you also have those patches for:- binutils (ld)- "[PR ld/22263] s390: Avoid dynamic TLS relocs in PIE" https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=26b1426577b5dcb32d149c64cca3e603b81948a9 (Tested by configure check above) Otherwise there will be a R_390_TLS_TPOFF relocation, which fails to be processed in _dl_relocate_static_pie() as static TLS map is not setup.- "s390: Add DT_JMPREL pointing to .rela.[i]plt with static-pie" https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d942d8db12adf4c9e5c7d9ed6496a779ece7149e (We can't test it in configure as we are not able to link a static PIE executable if the system glibc lacks static PIE support) Otherwise there won't be DT_JMPREL, DT_PLTRELA, DT_PLTRELASZ entries and the IFUNC symbols are not processed, which leads to crashes.

- kernel (the mentioned links to the commits belong to 5.19 merge window):- "s390/mmap: increase stack/mmap gap to 128MB" https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/commit/?h=features&id=f2f47d0ef72c30622e62471903ea19446ea79ee2- "s390/vdso: move vdso mapping to its own function" https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/commit/?h=features&id=57761da4dc5cd60bed2c81ba0edb7495c3c740b8- "s390/vdso: map vdso above stack" https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/commit/?h=features&id=9e37a2e8546f9e48ea76c839116fa5174d14e033- "s390/vdso: add vdso randomization" https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git/commit/?h=features&id=41cd81abafdc4e58a93fcb677712a76885e3ca25 (We can't test the kernel of the target system) Otherwise if /proc/sys/kernel/randomize_va_space is turned off (0), static PIE executables like ldconfig will crash. While startup sbrk is used to enlarge the HEAP. Unfortunately the underlying brk syscall fails as there is not enough space after the HEAP. Then the address of the TLS image is invalid and the following memcpy in __libc_setup_tls() leads to a segfault. If /proc/sys/kernel/randomize_va_space is activated (default: 2), there is enough space after HEAP.

- glibc- "Linux: Define MMAP_CALL_INTERNAL" https://sourceware.org/git/?p=glibc.git;a=commit;h=c1b68685d438373efe64e5f076f4215723004dfb- "i386: Remove OPTIMIZE_FOR_GCC_5 from Linux libc-do-syscall.S" https://sourceware.org/git/?p=glibc.git;a=commit;h=6e5c7a1e262961adb52443ab91bd2c9b72316402- "i386: Honor I386_USE_SYSENTER for 6-argument Linux system calls" https://sourceware.org/git/?p=glibc.git;a=commit;h=60f0f2130d30cfd008ca39743027f1e200592dff- "ia64: Always define IA64_USE_NEW_STUB as a flag macro" https://sourceware.org/git/?p=glibc.git;a=commit;h=18bd9c3d3b1b6a9182698c85354578d1d58e9d64- "Linux: Implement a useful version of _startup_fatal" https://sourceware.org/git/?p=glibc.git;a=commit;h=a2a6bce7d7e52c1c34369a7da62c501cc350bc31- "Linux: Introduce __brk_call for invoking the brk system call" https://sourceware.org/git/?p=glibc.git;a=commit;h=b57ab258c1140bc45464b4b9908713e3e0ee35aa- "csu: Implement and use _dl_early_allocate during static startup" https://sourceware.org/git/?p=glibc.git;a=commit;h=f787e138aa0bf677bf74fa2a08595c446292f3d7 The mentioned patch series by Florian Weimer avoids the mentioned failing sbrk syscall by falling back to mmap.

This commit also adjusts startup code in start.S to be ready for static PIE. We have to add a wrapper function for main as we are not allowed to use GOT relocations before __libc_start_main is called. (Compare also to:- commit 14d886edbd3d80b771e1c42fbd9217f9074de9c6 "aarch64: fix start code for static pie"- commit 3d1d79283e6de4f7c434cb67fb53a4fd28359669 "aarch64: fix static pie enabled libc when main is in a shared library" )

728894dba4 S390: Enable static PIE
sysdeps/s390/s390-64/configure | 122 ++++++++++++++++++++++++++++++++++++++
sysdeps/s390/s390-64/configure.ac | 92 ++++++++++++++++++++++++++++
sysdeps/s390/s390-64/start.S | 28 +++++++++
3 files changed, 242 insertions(+)

Upstream: sourceware.org

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