linux-kernel - [PATCH v3 1/2] livepatch, x86/module: Generalize late module relocation locking.

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Message-ID: <20250522184249.3137187-2-dylanbhatch@google.com>
Date: Thu, 22 May 2025 18:42:48 +0000
From: Dylan Hatch <dylanbhatch@...gle.com>
To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Josh Poimboeuf <jpoimboe@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
	Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>, 
	Joe Lawrence <joe.lawrence@...hat.com>
Cc: Dylan Hatch <dylanbhatch@...gle.com>, Song Liu <song@...nel.org>, 
	Ard Biesheuvel <ardb@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Peter Zijlstra <peterz@...radead.org>, "Mike Rapoport (Microsoft)" <rppt@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Dan Carpenter <dan.carpenter@...aro.org>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	live-patching@...r.kernel.org
Subject: [PATCH v3 1/2] livepatch, x86/module: Generalize late module
 relocation locking.

Late module relocations are an issue on any arch that supports
livepatch, so move the text_mutex locking to the livepatch core code.

Signed-off-by: Dylan Hatch <dylanbhatch@...gle.com>
---
 arch/x86/kernel/module.c |  8 ++------
 kernel/livepatch/core.c  | 18 +++++++++++++-----
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index ff07558b7ebc6..38767e0047d0c 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -197,18 +197,14 @@ static int write_relocate_add(Elf64_Shdr *sechdrs,
 	bool early = me->state == MODULE_STATE_UNFORMED;
 	void *(*write)(void *, const void *, size_t) = memcpy;
 
-	if (!early) {
+	if (!early)
 		write = text_poke;
-		mutex_lock(&text_mutex);
-	}
 
 	ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
 				   write, apply);
 
-	if (!early) {
+	if (!early)
 		text_poke_sync();
-		mutex_unlock(&text_mutex);
-	}
 
 	return ret;
 }
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 0e73fac55f8eb..9968441f73510 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -294,9 +294,10 @@ static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
 				    unsigned int symndx, unsigned int secndx,
 				    const char *objname, bool apply)
 {
-	int cnt, ret;
+	int cnt, ret = 0;
 	char sec_objname[MODULE_NAME_LEN];
 	Elf_Shdr *sec = sechdrs + secndx;
+	bool early = pmod->state == MODULE_STATE_UNFORMED;
 
 	/*
 	 * Format: .klp.rela.sec_objname.section_name
@@ -319,12 +320,19 @@ static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
 					  sec, sec_objname);
 		if (ret)
 			return ret;
-
-		return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
 	}
 
-	clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
-	return 0;
+	if (!early)
+		mutex_lock(&text_mutex);
+
+	if (apply)
+		ret = apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
+	else
+		clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
+
+	if (!early)
+		mutex_unlock(&text_mutex);
+	return ret;
 }
 
 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
-- 
2.49.0.1151.ga128411c76-goog