{"id":2219687,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2219687/?format=json","project":{"id":2,"url":"http://patchwork.ozlabs.org/api/1.0/projects/2/?format=json","name":"Linux PPC development","link_name":"linuxppc-dev","list_id":"linuxppc-dev.lists.ozlabs.org","list_email":"linuxppc-dev@lists.ozlabs.org","web_url":"https://github.com/linuxppc/wiki/wiki","scm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git","webscm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/"},"msgid":"<20260403190123.1383198-2-sourabhjain@linux.ibm.com>","date":"2026-04-03T19:01:16","name":"[v2,2/2] powerpc/vmx: avoid KASAN instrumentation in enter_vmx_ops() for kexec","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"d9e748876e98e6d169a17b0f3b899f24c263464f","submitter":{"id":77202,"url":"http://patchwork.ozlabs.org/api/1.0/people/77202/?format=json","name":"Sourabh Jain","email":"sourabhjain@linux.ibm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260403190123.1383198-2-sourabhjain@linux.ibm.com/mbox/","series":[{"id":498664,"url":"http://patchwork.ozlabs.org/api/1.0/series/498664/?format=json","date":"2026-04-03T19:01:15","name":"[v2,1/2] powerpc/kdump: fix KASAN sanitization flag for core_$(BITS).o","version":2,"mbox":"http://patchwork.ozlabs.org/series/498664/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2219687/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=JHzN5lF8;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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In this context, code must not rely on normal virtual address\ntranslations or trigger page faults.\n\nWith KASAN enabled, functions get instrumented and may access shadow\nmemory using regular address translation. When executed with the MMU\noff, this can lead to page faults (bad_page_fault) from which the\nkernel cannot recover in the kexec path, resulting in a hang.\n\nThe kexec path sets preempt_count to HARDIRQ_OFFSET before entering\nthe MMU-off copy sequence.\n\ncurrent_thread_info()->preempt_count = HARDIRQ_OFFSET\n kexec_sequence(..., copy_with_mmu_off = 1)\n -> kexec_copy_flush(image)\n copy_segments()\n -> copy_page(dest, addr)\n\t bl enter_vmx_ops()\n if (in_interrupt())\n return 0\n\t beq .Lnonvmx_copy\n\nSince kexec sets preempt_count to HARDIRQ_OFFSET, in_interrupt()\nevaluates to true and enter_vmx_ops() returns early.\n\nAs in_interrupt() (and preempt_count()) are always inlined, mark\nenter_vmx_ops() with __no_sanitize_address to avoid KASAN\ninstrumentation and shadow memory access with MMU disabled, helping\nkexec boot fine with KASAN enabled.\n\nCc: Aditya Gupta \nCc: Daniel Axtens \nCc: Hari Bathini \nCc: Madhavan Srinivasan \nCc: Mahesh Salgaonkar \nCc: Michael Ellerman \nCc: Ritesh Harjani (IBM) \nCc: Shivang Upadhyay \nCc: Venkat Rao Bagalkote \nReported-by: Aboorva Devarajan \nSigned-off-by: Sourabh Jain \n---\nChangelog:\n\nv2:\n- Remove __no_sanitize_address from exit_vmx_ops\n- Add a comment explaining that marking only enter_vmx_ops\n with __no_sanitize_address is sufficient for kexec to\n function properly with KASAN enabled\n\nv1:\nhttps://lore.kernel.org/all/20260321053121.614022-1-sourabhjain@linux.ibm.com/\n---\n arch/powerpc/lib/vmx-helper.c | 9 ++++++++-\n 1 file changed, 8 insertions(+), 1 deletion(-)","diff":"diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c\nindex 554b248002b4..57e897b60db8 100644\n--- a/arch/powerpc/lib/vmx-helper.c\n+++ b/arch/powerpc/lib/vmx-helper.c\n@@ -52,7 +52,14 @@ int exit_vmx_usercopy(void)\n }\n EXPORT_SYMBOL(exit_vmx_usercopy);\n \n-int enter_vmx_ops(void)\n+/*\n+ * Can be called from kexec copy_page() path with MMU off. The kexec\n+ * code sets preempt_count to HARDIRQ_OFFSET so we return early here.\n+ * Since in_interrupt() is always inline, __no_sanitize_address on this\n+ * function is sufficient to avoid KASAN shadow memory accesses in real\n+ * mode.\n+ */\n+int __no_sanitize_address enter_vmx_ops(void)\n {\n \tif (in_interrupt())\n \t\treturn 0;\n","prefixes":["v2","2/2"]}