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Message-ID: <9da1e9f592aadc8fbf48b7429e3fbcea4606a76a.1746821544.git.jpoimboe@kernel.org>
Date: Fri, 9 May 2025 13:17:06 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
Petr Mladek <pmladek@...e.com>,
Miroslav Benes <mbenes@...e.cz>,
Joe Lawrence <joe.lawrence@...hat.com>,
live-patching@...r.kernel.org,
Song Liu <song@...nel.org>,
laokz <laokz@...mail.com>,
Jiri Kosina <jikos@...nel.org>,
Marcos Paulo de Souza <mpdesouza@...e.com>,
Weinan Liu <wnliu@...gle.com>,
Fazla Mehrab <a.mehrab@...edance.com>,
Chen Zhongjin <chenzhongjin@...wei.com>,
Puranjay Mohan <puranjay@...nel.org>,
Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH v2 42/62] kbuild,x86: Fix module permissions for __jump_table and __bug_table
An upcoming patch will add the SHF_MERGE flag to x86 __jump_table and
__bug_table so their entry sizes can be defined in inline asm.
However, those sections have SHF_WRITE, which the Clang linker (lld)
explicitly forbids combining with SHF_MERGE.
Those sections are modified at runtime and must remain writable. While
SHF_WRITE is ignored by vmlinux, it's still needed for modules.
To work around the linker interference, remove SHF_WRITE during
compilation and restore it after linking the module.
Cc: Masahiro Yamada <masahiroy@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
arch/Kconfig | 3 +++
arch/x86/Kconfig | 1 +
arch/x86/include/asm/bug.h | 4 ++--
arch/x86/include/asm/jump_label.h | 2 +-
scripts/Makefile.modfinal | 18 +++++++++++++-----
5 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index b0adb665041f..a413cd86f87c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1314,6 +1314,9 @@ config HAVE_NOINSTR_HACK
config HAVE_NOINSTR_VALIDATION
bool
+config NEED_MODULE_PERMISSIONS_FIX
+ bool
+
config HAVE_UACCESS_VALIDATION
bool
select OBJTOOL
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4c33c644b92d..996d59e59e5d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -309,6 +309,7 @@ config X86
select HOTPLUG_SPLIT_STARTUP if SMP && X86_32
select IRQ_FORCED_THREADING
select LOCK_MM_AND_FIND_VMA
+ select NEED_MODULE_PERMISSIONS_FIX
select NEED_PER_CPU_EMBED_FIRST_CHUNK
select NEED_PER_CPU_PAGE_FIRST_CHUNK
select NEED_SG_DMA_LENGTH
diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index f0e9acf72547..fb3534ddbea2 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -42,7 +42,7 @@
#define _BUG_FLAGS(ins, flags, extra) \
do { \
asm_inline volatile("1:\t" ins "\n" \
- ".pushsection __bug_table,\"aw\"\n" \
+ ".pushsection __bug_table,\"a\"\n" \
"2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \
"\t" __BUG_REL(%c0) "\t# bug_entry::file\n" \
"\t.word %c1" "\t# bug_entry::line\n" \
@@ -60,7 +60,7 @@ do { \
#define _BUG_FLAGS(ins, flags, extra) \
do { \
asm_inline volatile("1:\t" ins "\n" \
- ".pushsection __bug_table,\"aw\"\n" \
+ ".pushsection __bug_table,\"a\"\n" \
"2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \
"\t.word %c0" "\t# bug_entry::flags\n" \
"\t.org 2b+%c1\n" \
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 61dd1dee7812..cd21554b3675 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -13,7 +13,7 @@
#include <linux/types.h>
#define JUMP_TABLE_ENTRY(key, label) \
- ".pushsection __jump_table, \"aw\" \n\t" \
+ ".pushsection __jump_table, \"a\"\n\t" \
_ASM_ALIGN "\n\t" \
".long 1b - . \n\t" \
".long " label " - . \n\t" \
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 542ba462ed3e..878d0d25a461 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -28,12 +28,23 @@ ccflags-remove-y := $(CC_FLAGS_CFI)
.module-common.o: $(srctree)/scripts/module-common.c FORCE
$(call if_changed_rule,cc_o_c)
+ifdef CONFIG_NEED_MODULE_PERMISSIONS_FIX
+cmd_fix_mod_permissions = \
+ $(OBJCOPY) --set-section-flags __jump_table=alloc,data \
+ --set-section-flags __bug_table=alloc,data $@
+endif
+
quiet_cmd_ld_ko_o = LD [M] $@
cmd_ld_ko_o = \
$(LD) -r $(KBUILD_LDFLAGS) \
$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
-T $(objtree)/scripts/module.lds -o $@ $(filter %.o, $^)
+define rule_ld_ko_o
+ $(call cmd_and_savecmd,ld_ko_o)
+ $(call cmd,fix_mod_permissions)
+endef
+
quiet_cmd_btf_ko = BTF [M] $@
cmd_btf_ko = \
if [ ! -f $(objtree)/vmlinux ]; then \
@@ -46,14 +57,11 @@ quiet_cmd_btf_ko = BTF [M] $@
# Same as newer-prereqs, but allows to exclude specified extra dependencies
newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
-# Same as if_changed, but allows to exclude specified extra dependencies
-if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
- $(cmd); \
- printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
+if_changed_rule_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),$(rule_$(1)),@:)
# Re-generate module BTFs if either module's .ko or vmlinux changed
%.ko: %.o %.mod.o .module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
- +$(call if_changed_except,ld_ko_o,$(objtree)/vmlinux)
+ +$(call if_changed_rule_except,ld_ko_o,$(objtree)/vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+$(if $(newer-prereqs),$(call cmd,btf_ko))
endif
--
2.49.0
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