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Peter Anvin" , Peter Zijlstra , Uros Bizjak , Brian Gerst Subject: [PATCH 0/9] x86-64: Stack protector and percpu improvements Date: Mon, 23 Oct 2023 17:17:21 -0400 Message-ID: <20231023211730.40566-1-brgerst@gmail.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Mon, 23 Oct 2023 14:17:59 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1780582593649157311 X-GMAIL-MSGID: 1780582593649157311 Currently, x86-64 uses an unusual per-cpu layout, where the percpu section is linked at absolute address 0. The reason behind this is that older GCC versions placed the stack protector (if enabled) at a fixed offset from the GS segment base. Since the GS segement is also used for percpu variables, this forced the current layout. GCC since version 8.1 supports a configurable location for the stack protector value, which allows removal of the restriction on how the percpu section is linked. This allows the percpu section to be linked normally, like most other architectures. In turn, this allows removal of code that was needed to support the zero-based percpu section. P.S.: I posted this series back in 2021, and at the time it appeared that GCC 8.1 was too recent (released May 2, 2018) to be a requirement to keep stack protector support. Two years later, support for the new compiler options should be much more widespread. Brian Gerst (9): x86/stackprotector/32: Remove stack protector test script x86/boot: Disable stack protector for early boot code x86/stackprotector/64: Convert stack protector to normal percpu variable x86/percpu/64: Remove fixed_percpu_data x86/percpu/64: Use relative percpu offsets x86/boot/64: Remove inverse relocations x86/percpu/64: Remove INIT_PER_CPU macros percpu: Remove PER_CPU_FIRST_SECTION kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU arch/x86/Kconfig | 7 +- arch/x86/Makefile | 19 +-- arch/x86/boot/compressed/misc.c | 14 +-- arch/x86/entry/entry_64.S | 2 +- arch/x86/include/asm/percpu.h | 22 ---- arch/x86/include/asm/processor.h | 28 +---- arch/x86/include/asm/stackprotector.h | 37 ++---- arch/x86/kernel/Makefile | 2 + arch/x86/kernel/asm-offsets_64.c | 6 - arch/x86/kernel/cpu/common.c | 8 +- arch/x86/kernel/head_64.S | 10 +- arch/x86/kernel/irq_64.c | 1 - arch/x86/kernel/setup_percpu.c | 12 +- arch/x86/kernel/vmlinux.lds.S | 35 ------ arch/x86/tools/relocs.c | 136 +--------------------- arch/x86/xen/xen-head.S | 6 +- include/asm-generic/vmlinux.lds.h | 1 - include/linux/percpu-defs.h | 12 -- init/Kconfig | 11 +- kernel/kallsyms.c | 12 +- scripts/gcc-x86_32-has-stack-protector.sh | 8 -- scripts/gcc-x86_64-has-stack-protector.sh | 4 - scripts/kallsyms.c | 80 +++---------- scripts/link-vmlinux.sh | 4 - 24 files changed, 60 insertions(+), 417 deletions(-) delete mode 100755 scripts/gcc-x86_32-has-stack-protector.sh delete mode 100755 scripts/gcc-x86_64-has-stack-protector.sh