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Mon, 26 Oct 2026 10:29:52 +0000 (GMT) Received: from tuxmaker.lnxne.boe (unknown [9.87.85.9]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 26 Oct 2026 10:29:52 +0000 (GMT) From: Heiko Carstens To: Alexander Gordeev , Sven Schnelle , Vasily Gorbik , Christian Borntraeger Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: [PATCH] s390: Use static call trampolines when kCFI is enabled Date: Mon, 26 Oct 2026 11:29:51 +0100 Message-ID: <20261026102952.4153711-1-hca@linux.ibm.com> X-Mailer: git-send-email 2.53.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=P8SvFSAu c=1 sm=1 tr=0 ts=6adf2ba8 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=Paj0-Z-736eVyoMAdw0A:9 X-Proofpoint-GUID: 8VvyADv0BpM_H3fYzMtTedcr-mFhQLUg X-Proofpoint-Spam-Info: AW1haW4tMjYxMDI2MDA0MCBTYWx0ZWRfXznL9VCYM5NW5 nx0FGm3pEkdKj7JNAeYPIE5cA6whRwc9EC8tY2Q0+CmD05DWS0ItAP/+pbIoyQdq5qBK5DmkUdd 9WdzDcZy75zuxirq8qGtRni5L/Rx9mM= X-Proofpoint-ORIG-GUID: 8VvyADv0BpM_H3fYzMtTedcr-mFhQLUg X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDI2MDA0MCBTYWx0ZWRfX6Unq1l4VT5Pq MAnfdIHSefUqO+vK8xniLSCLoJZUs5a3sWWcHZFxo/0a0lsWZF3O9mYnJmeojWHNHTbw2n2O2E5 bmhYwXKm/YcWrtMDesqXF9IxV8V2/f2gSF8tuGg7D1jvhvN0XivVjHveQaFFA6whnGhJlIMxEc8 Sfp8zrEeSiAYguhDKBDY+yDpXkkDz3WV5bghh1wqb0FMUssSXOBYrk4CMU23qALR4bEN2Gi/Z3y pR7Qi/4O69PKK+TjXD8oT2PVoRBPjwM616XWlUX81tPkFNoykZvXEf/BG9Vd4fCUXdNVTHbZkmH 4xxylqZE92nPDMDy7EEpP2l8S9rw0q10zLtAIpRHdQzfk0kg7BOotwDAPfg6u1sSf+9xV7tkIHk +tZNmw0YxsRbhe7XT57jsPxQUg/g0ArnDe9a0UID91aQH6ZYv0nI/+kAJrz+NMdSNv9nIYZPI21 DnvRoFZhQtBjebxUoVA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-26_01,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 malwarescore=0 phishscore=0 spamscore=0 clxscore=1015 bulkscore=0 suspectscore=0 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610260040 Add support for the 'unoptimized' static call variety, which routes all calls through a trampoline that performs a tail call to the chosen function. Wire it up for use when kCFI is enabled to work around an issue where the prototypes of default handlers such as __static_call_nop() and __static_call_ret0() don't match the expected prototype of the call site, resulting in kCFI false positives. This is the s390 version of commit 54ac9ff8f119 ("arm64: Use static call trampolines when kCFI is enabled"). Signed-off-by: Heiko Carstens --- arch/s390/Kconfig | 1 + arch/s390/include/asm/static_call.h | 39 +++++++++++++++++++++++++++++ arch/s390/kernel/Makefile | 1 + arch/s390/kernel/static_call.c | 20 +++++++++++++++ arch/s390/kernel/vmlinux.lds.S | 1 + 5 files changed, 62 insertions(+) create mode 100644 arch/s390/include/asm/static_call.h create mode 100644 arch/s390/kernel/static_call.c diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 10ada552d870..5d096a5eb48c 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -257,6 +257,7 @@ config S390 select HAVE_SETUP_PER_CPU_AREA select HAVE_SOFTIRQ_ON_OWN_STACK select HAVE_STACKPROTECTOR if CC_HAS_STACKPROTECTOR_GLOBAL + select HAVE_STATIC_CALL if CFI select HAVE_SYSCALL_TRACEPOINTS select HAVE_VIRT_CPU_ACCOUNTING select HAVE_VIRT_CPU_ACCOUNTING_IDLE diff --git a/arch/s390/include/asm/static_call.h b/arch/s390/include/asm/static_call.h new file mode 100644 index 000000000000..6e196cd18240 --- /dev/null +++ b/arch/s390/include/asm/static_call.h @@ -0,0 +1,39 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_S390_STATIC_CALL_H +#define _ASM_S390_STATIC_CALL_H + +#ifdef CC_USING_EXPOLINE +#define __STATIC_CALL_BR_EX_R1 \ + "557: jg __s390_indirect_jump_r1\n" \ + " .pushsection .s390_indirect_branches,\"a\",@progbits\n" \ + " .long 557b-.\n" \ + " .popsection\n" +#else +#define __STATIC_CALL_BR_EX_R1 " br %r1\n" +#endif + +#define __ARCH_DEFINE_STATIC_CALL_TRAMP(name, target) \ + asm(" .pushsection .static_call.text, \"ax\"\n" \ + " .balign 4\n" \ + " .globl " name "\n" \ + name ":\n" \ + " lgrl %r1,1f\n" \ + __STATIC_CALL_BR_EX_R1 \ + " .type " name ", @function\n" \ + " .size " name ", . - " name "\n" \ + " .popsection\n" \ + " .pushsection .rodata, \"a\"\n" \ + " .balign 8\n" \ + "1: .quad " target "\n" \ + " .popsection\n") + +#define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func) \ + __ARCH_DEFINE_STATIC_CALL_TRAMP(STATIC_CALL_TRAMP_STR(name), #func) + +#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \ + ARCH_DEFINE_STATIC_CALL_TRAMP(name, __static_call_return0) + +#define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name) \ + ARCH_DEFINE_STATIC_CALL_TRAMP(name, __static_call_return0) + +#endif /* _ASM_S390_STATIC_CALL_H */ diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index f84b8fb41331..a8800319033d 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -70,6 +70,7 @@ obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o obj-$(CONFIG_UPROBES) += uprobes.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o +obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o obj-$(CONFIG_STACKPROTECTOR) += stackprotector.o obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o kexec_image.o obj-$(CONFIG_KEXEC_FILE) += kexec_elf.o diff --git a/arch/s390/kernel/static_call.c b/arch/s390/kernel/static_call.c new file mode 100644 index 000000000000..e8e20e4f782f --- /dev/null +++ b/arch/s390/kernel/static_call.c @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include + +struct insn_ril { + u16 opc; + s32 ri2; +} __packed; + +void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) +{ + struct insn_ril *insn = tramp; + void *literal; + + literal = tramp + insn->ri2 * 2; + if (!func) + func = __static_call_return0; + s390_kernel_write(literal, &func, sizeof(func)); +} +EXPORT_SYMBOL_GPL(arch_static_call_transform); diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S index 1f0e71c58eb9..b9d58441f669 100644 --- a/arch/s390/kernel/vmlinux.lds.S +++ b/arch/s390/kernel/vmlinux.lds.S @@ -48,6 +48,7 @@ SECTIONS SCHED_TEXT LOCK_TEXT KPROBES_TEXT + STATIC_CALL_TEXT IRQENTRY_TEXT SOFTIRQENTRY_TEXT FTRACE_HOTPATCH_TRAMPOLINES_TEXT -- 2.53.0