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From: Sami Tolvanen <samitolvanen@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
	Will Deacon <will@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com,
	kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, x86@kernel.org,
	Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH v5 16/29] init: lto: fix PREL32 relocations
Date: Fri,  9 Oct 2020 09:13:25 -0700
Message-ID: <20201009161338.657380-17-samitolvanen@google.com> (raw)
In-Reply-To: <20201009161338.657380-1-samitolvanen@google.com>

With LTO, the compiler can rename static functions to avoid global
naming collisions. As initcall functions are typically static,
renaming can break references to them in inline assembly. This
change adds a global stub with a stable name for each initcall to
fix the issue when PREL32 relocations are used.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 include/linux/init.h | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/include/linux/init.h b/include/linux/init.h
index af638cd6dd52..cea63f7e7705 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -209,26 +209,49 @@ extern bool initcall_debug;
  */
 #define __initcall_section(__sec, __iid)			\
 	#__sec ".init.." #__iid
+
+/*
+ * With LTO, the compiler can rename static functions to avoid
+ * global naming collisions. We use a global stub function for
+ * initcalls to create a stable symbol name whose address can be
+ * taken in inline assembly when PREL32 relocations are used.
+ */
+#define __initcall_stub(fn, __iid, id)				\
+	__initcall_name(initstub, __iid, id)
+
+#define __define_initcall_stub(__stub, fn)			\
+	int __init __stub(void);				\
+	int __init __stub(void)					\
+	{ 							\
+		return fn();					\
+	}							\
+	__ADDRESSABLE(__stub)
 #else
 #define __initcall_section(__sec, __iid)			\
 	#__sec ".init"
+
+#define __initcall_stub(fn, __iid, id)	fn
+
+#define __define_initcall_stub(__stub, fn)			\
+	__ADDRESSABLE(fn)
 #endif
 
 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define ____define_initcall(fn, __name, __sec)			\
-	__ADDRESSABLE(fn)					\
+#define ____define_initcall(fn, __stub, __name, __sec)		\
+	__define_initcall_stub(__stub, fn)			\
 	asm(".section	\"" __sec "\", \"a\"		\n"	\
 	    __stringify(__name) ":			\n"	\
-	    ".long	" #fn " - .			\n"	\
+	    ".long	" __stringify(__stub) " - .	\n"	\
 	    ".previous					\n");
 #else
-#define ____define_initcall(fn, __name, __sec)			\
+#define ____define_initcall(fn, __unused, __name, __sec)	\
 	static initcall_t __name __used 			\
 		__attribute__((__section__(__sec))) = fn;
 #endif
 
 #define __unique_initcall(fn, id, __sec, __iid)			\
 	____define_initcall(fn,					\
+		__initcall_stub(fn, __iid, id),			\
 		__initcall_name(initcall, __iid, id),		\
 		__initcall_section(__sec, __iid))
 
-- 
2.28.0.1011.ga647a8990f-goog


  parent reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 04/29] tracing: move function tracer options to Kconfig Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 05/29] tracing: add support for objtool mcount Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 06/29] x86, build: use " Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 07/29] treewide: remove DISABLE_LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 08/29] kbuild: add support for Clang LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 09/29] kbuild: lto: fix module versioning Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 11/29] kbuild: lto: postpone objtool Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 12/29] kbuild: lto: limit inlining Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 13/29] kbuild: lto: merge module sections Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 15/29] init: lto: ensure initcall ordering Sami Tolvanen
2020-10-09 16:13 ` Sami Tolvanen [this message]
2020-10-09 16:13 ` [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 18/29] modpost: lto: strip .lto from module names Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 19/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 20/29] efi/libstub: disable LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 22/29] arm64: vdso: disable LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-10-12  8:31   ` Will Deacon
2020-10-12 20:44     ` Kees Cook
2020-10-12 20:51       ` Will Deacon
2020-10-12 21:02         ` Kees Cook
2020-10-09 16:13 ` [PATCH v5 26/29] x86/asm: annotate indirect jumps Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-10-09 16:30 ` [PATCH v5 00/29] Add support for Clang LTO Sedat Dilek
2020-10-09 20:50   ` Sami Tolvanen
     [not found] ` <20201009153512.1546446a@gandalf.local.home>
2020-10-09 21:05   ` Sami Tolvanen
2020-10-09 23:38     ` Steven Rostedt
2020-10-10  0:00       ` Sami Tolvanen

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