linux-kernel - [RFC PATCH 47/56] x86/module: Add ITS re-patch support for modules

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Message-ID: <20251013143444.3999-48-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:35 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
	<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: Alexander Graf <graf@...zon.com>, Boris Ostrovsky
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 47/56] x86/module: Add ITS re-patch support for modules

When re-patching modules, call the appropriate functions related to ITS
mitigation support.

The ITS mitigation is unique because it requires memory operations that are
not possible under NMI context.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/module.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index b6beb2b3469c..12a934755097 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -390,4 +390,36 @@ void arch_module_update_alternatives(struct module *mod)
 		apply_alternatives(aseg, aseg + alt->sh_size, mod);
 	}
 }
+
+void arch_module_pre_update_alternatives(struct module *mod)
+{
+	const Elf_Ehdr *hdr;
+	const Elf_Shdr *sechdrs;
+	const Elf_Shdr *s;
+	char *secstrings;
+
+	if (!mod->klp_info) {
+		pr_warn("No module livepatch info, unable to update alternatives\n");
+		return;
+	}
+
+	hdr = &mod->klp_info->hdr;
+	sechdrs = mod->klp_info->sechdrs;
+	secstrings = mod->klp_info->secstrings;
+
+	for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
+		if (!strcmp(".retpoline_sites", secstrings + s->sh_name)) {
+			void *rseg = (void *)s->sh_addr;
+
+			its_init_mod(mod);
+			its_prealloc(rseg, rseg + s->sh_size, mod);
+			its_fini_mod(mod);
+		}
+	}
+}
+
+void arch_module_post_update_alternatives(struct module *mod)
+{
+	its_free_all(mod);
+}
 #endif
-- 
2.34.1