linux-kernel - [PATCH 4.19 52/67] vmlinux.lds.h: Avoid orphan section with !SMP

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Date:   Mon, 14 Jun 2021 12:27:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 4.19 52/67] vmlinux.lds.h: Avoid orphan section with !SMP

From: Nathan Chancellor <nathan@...nel.org>

commit d4c6399900364facd84c9e35ce1540b6046c345f upstream.

With x86_64_defconfig and the following configs, there is an orphan
section warning:

CONFIG_SMP=n
CONFIG_AMD_MEM_ENCRYPT=y
CONFIG_HYPERVISOR_GUEST=y
CONFIG_KVM=y
CONFIG_PARAVIRT=y

ld: warning: orphan section `.data..decrypted' from `arch/x86/kernel/cpu/vmware.o' being placed in section `.data..decrypted'
ld: warning: orphan section `.data..decrypted' from `arch/x86/kernel/kvm.o' being placed in section `.data..decrypted'

These sections are created with DEFINE_PER_CPU_DECRYPTED, which
ultimately turns into __PCPU_ATTRS, which in turn has a section
attribute with a value of PER_CPU_BASE_SECTION + the section name. When
CONFIG_SMP is not set, the base section is .data and that is not
currently handled in any linker script.

Add .data..decrypted to PERCPU_DECRYPTED_SECTION, which is included in
PERCPU_INPUT -> PERCPU_SECTION, which is include in the x86 linker
script when either CONFIG_X86_64 or CONFIG_SMP is unset, taking care of
the warning.

Fixes: ac26963a1175 ("percpu: Introduce DEFINE_PER_CPU_DECRYPTED")
Link: https://github.com/ClangBuiltLinux/linux/issues/1360
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com> # build
Signed-off-by: Kees Cook <keescook@...omium.org>
Link: https://lore.kernel.org/r/20210506001410.1026691-1-nathan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/asm-generic/vmlinux.lds.h |    1 +
 1 file changed, 1 insertion(+)

--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -842,6 +842,7 @@
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 #define PERCPU_DECRYPTED_SECTION					\
 	. = ALIGN(PAGE_SIZE);						\
+	*(.data..decrypted)						\
 	*(.data..percpu..decrypted)					\
 	. = ALIGN(PAGE_SIZE);
 #else