Bug 1726638
Summary: | glibc: Implement SVE Vector PCS on AArch64 | ||
---|---|---|---|
Product: | Red Hat Enterprise Linux 8 | Reporter: | Nick Clifton <nickc> |
Component: | glibc | Assignee: | Florian Weimer <fweimer> |
Status: | CLOSED ERRATA | QA Contact: | qe-baseos-tools-bugs |
Severity: | medium | Docs Contact: | |
Priority: | high | ||
Version: | 8.2 | CC: | ashankar, codonell, dj, fweimer, jfeeney, mnewsome, pfrankli, skolosov, tgummels, woodard |
Target Milestone: | rc | Keywords: | FutureFeature, Patch, Triaged |
Target Release: | 8.2 | ||
Hardware: | aarch64 | ||
OS: | Linux | ||
Whiteboard: | |||
Fixed In Version: | glibc-2.28-86.el8 | Doc Type: | No Doc Update |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2020-04-28 16:50:14 UTC | Type: | Bug |
Regression: | --- | Mount Type: | --- |
Documentation: | --- | CRM: | |
Verified Versions: | Category: | --- | |
oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
Cloudforms Team: | --- | Target Upstream Version: | |
Embargoed: | |||
Bug Depends On: | 1382435 | ||
Bug Blocks: | 1543699, 1618515, 1683831, 1687244, 1746605, 1746913, 1755139, 1776957 |
Description
Nick Clifton
2019-07-03 10:41:52 UTC
*** Bug 1383683 has been marked as a duplicate of this bug. *** commit 30ba0375464f34e4bf8129f3d3dc14d0c09add17 Author: Szabolcs Nagy <szabolcs.nagy> Date: Tue Jul 9 12:11:39 2019 +0100 aarch64: simplify the DT_AARCH64_VARIANT_PCS handling code Remove unnecessary variant_pcs field: the dynamic tag can be checked directly. * sysdeps/aarch64/dl-machine.h (elf_machine_runtime_setup): Remove the DT_AARCH64_VARIANT_PCS check. (elf_machine_lazy_rel): Use l_info[DT_AARCH64 (VARIANT_PCS)]. * sysdeps/aarch64/linkmap.h (struct link_map_machine): Remove variant_pcs. commit 82bc69c012838a381c4167c156a06f4598f34227 Author: Szabolcs Nagy <szabolcs.nagy> Date: Thu Apr 25 15:35:35 2019 +0100 aarch64: handle STO_AARCH64_VARIANT_PCS Avoid lazy binding of symbols that may follow a variant PCS with different register usage convention from the base PCS. Currently the lazy binding entry code does not preserve all the registers required for AdvSIMD and SVE vector calls. Saving and restoring all registers unconditionally may break existing binaries, even if they never use vector calls, because of the larger stack requirement for lazy resolution, which can be significant on an SVE system. The solution is to mark all symbols in the symbol table that may follow a variant PCS so the dynamic linker can handle them specially. In this patch such symbols are always resolved at load time, not lazily. So currently LD_AUDIT for variant PCS symbols are not supported, for that the _dl_runtime_profile entry needs to be changed e.g. to unconditionally save/restore all registers (but pass down arg and retval registers to pltentry/exit callbacks according to the base PCS). This patch also removes a __builtin_expect from the modified code because the branch prediction hint did not seem useful. * sysdeps/aarch64/dl-dtprocnum.h: New file. * sysdeps/aarch64/dl-machine.h (DT_AARCH64): Define. (elf_machine_runtime_setup): Handle DT_AARCH64_VARIANT_PCS. (elf_machine_lazy_rel): Check STO_AARCH64_VARIANT_PCS and bind such symbols at load time. * sysdeps/aarch64/linkmap.h (struct link_map_machine): Add variant_pcs. commit 55f82d328d2dd1c7c13c1992f4b9bf9c95b57551 Author: Szabolcs Nagy <szabolcs.nagy> Date: Thu Apr 25 15:35:35 2019 +0100 aarch64: add STO_AARCH64_VARIANT_PCS and DT_AARCH64_VARIANT_PCS STO_AARCH64_VARIANT_PCS is a non-visibility st_other flag for marking symbols that reference functions that may follow a variant PCS with different register usage convention from the base PCS. DT_AARCH64_VARIANT_PCS is a dynamic tag that marks ELF modules that have R_*_JUMP_SLOT relocations for symbols marked with STO_AARCH64_VARIANT_PCS (i.e. have variant PCS calls via a PLT). * elf/elf.h (STO_AARCH64_VARIANT_PCS): Define. (DT_AARCH64_VARIANT_PCS): Define. Verified by checking /usr/include/elf.h, it contains DT_AARCH64_VARIANT_PCS and STO_AARCH64_VARIANT_PCS definitions. Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHSA-2020:1828 |