linux-kernel - [PATCH 3/4] vmlinux.lds.h: Fix alignment for __ksymtab*, __kcrctab_* and .pci

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Date:   Wed, 22 Nov 2023 23:18:13 +0100
From:   deller@...nel.org
To:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-modules@...r.kernel.org,
        linux-arch@...r.kernel.org, Luis Chamberlain <mcgrof@...nel.org>
Subject: [PATCH 3/4] vmlinux.lds.h: Fix alignment for __ksymtab*, __kcrctab_* and .pci_fixup sections

From: Helge Deller <deller@....de>

On 64-bit architectures without CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
(e.g. ppc64, ppc64le, parisc, s390x,...) the __KSYM_REF() macro stores
64-bit pointers into the __ksymtab* sections.
Make sure that the start of those sections is 64-bit aligned in the vmlinux
executable, otherwise unaligned memory accesses may happen at runtime.

The __kcrctab* sections store 32-bit entities, so make those sections
32-bit aligned.

The pci fixup routines want to be 64-bit aligned on 64-bit platforms
which don't define CONFIG_HAVE_ARCH_PREL32_RELOCATIONS. An alignment
of 8 bytes is sufficient to guarantee aligned accesses at runtime.

Signed-off-by: Helge Deller <deller@....de>
Cc: <stable@...r.kernel.org> # v6.0+
---
 include/asm-generic/vmlinux.lds.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index bae0fe4d499b..fa4335346e7d 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -467,6 +467,7 @@
 	}								\
 									\
 	/* PCI quirks */						\
+	. = ALIGN(8);							\
 	.pci_fixup        : AT(ADDR(.pci_fixup) - LOAD_OFFSET) {	\
 		BOUNDED_SECTION_PRE_LABEL(.pci_fixup_early,  _pci_fixups_early,  __start, __end) \
 		BOUNDED_SECTION_PRE_LABEL(.pci_fixup_header, _pci_fixups_header, __start, __end) \
@@ -484,6 +485,7 @@
 	PRINTK_INDEX							\
 									\
 	/* Kernel symbol table: Normal symbols */			\
+	. = ALIGN(8);							\
 	__ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {		\
 		__start___ksymtab = .;					\
 		KEEP(*(SORT(___ksymtab+*)))				\
@@ -491,6 +493,7 @@
 	}								\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
+	. = ALIGN(8);							\
 	__ksymtab_gpl     : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) {	\
 		__start___ksymtab_gpl = .;				\
 		KEEP(*(SORT(___ksymtab_gpl+*)))				\
@@ -498,6 +501,7 @@
 	}								\
 									\
 	/* Kernel symbol table: Normal symbols */			\
+	. = ALIGN(4);							\
 	__kcrctab         : AT(ADDR(__kcrctab) - LOAD_OFFSET) {		\
 		__start___kcrctab = .;					\
 		KEEP(*(SORT(___kcrctab+*)))				\
@@ -505,6 +509,7 @@
 	}								\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
+	. = ALIGN(4);							\
 	__kcrctab_gpl     : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) {	\
 		__start___kcrctab_gpl = .;				\
 		KEEP(*(SORT(___kcrctab_gpl+*)))				\
-- 
2.41.0