| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 5.0 247/262] x86/build: Mark per-CPU symbols as absolute explicitly for LLD | Date | Wed, 27 Mar 2019 14:01:42 -0400 |
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From: Rafael Ávila de Espíndola <rafael@espindo.la>
[ Upstream commit d071ae09a4a1414c1433d5ae9908959a7325b0ad ]
Accessing per-CPU variables is done by finding the offset of the variable in the per-CPU block and adding it to the address of the respective CPU's block.
Section 3.10.8 of ld.bfd's documentation states:
For expressions involving numbers, relative addresses and absolute addresses, ld follows these rules to evaluate terms:
Other binary operations, that is, between two relative addresses not in the same section, or between a relative address and an absolute address, first convert any non-absolute term to an absolute address before applying the operator."
Note that LLVM's linker does not adhere to the GNU ld's implementation and as such requires implicitly-absolute terms to be explicitly marked as absolute in the linker script. If not, it fails currently with:
ld.lld: error: ./arch/x86/kernel/vmlinux.lds:153: at least one side of the expression must be absolute ld.lld: error: ./arch/x86/kernel/vmlinux.lds:154: at least one side of the expression must be absolute Makefile:1040: recipe for target 'vmlinux' failed
This is not a functional change for ld.bfd which converts the term to an absolute symbol anyways as specified above.
Based on a previous submission by Tri Vo <trong@android.com>.
Reported-by: Dmitry Golovin <dima@golovin.in> Signed-off-by: Rafael Ávila de Espíndola <rafael@espindo.la> [ Update commit message per Boris' and Michael's suggestions. ] Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> [ Massage commit message more, fix typos. ] Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Dmitry Golovin <dima@golovin.in> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Cao Jin <caoj.fnst@cn.fujitsu.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tri Vo <trong@android.com> Cc: dima@golovin.in Cc: morbo@google.com Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20181219190145.252035-1-ndesaulniers@google.com Signed-off-by: Sasha Levin <sashal@kernel.org> --- arch/x86/kernel/vmlinux.lds.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 0d618ee634ac..ee3b5c7d662e 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -401,7 +401,7 @@ SECTIONS * Per-cpu symbols which need to be offset from __per_cpu_load * for the boot processor. */ -#define INIT_PER_CPU(x) init_per_cpu__##x = x + __per_cpu_load +#define INIT_PER_CPU(x) init_per_cpu__##x = ABSOLUTE(x) + __per_cpu_load INIT_PER_CPU(gdt_page); INIT_PER_CPU(irq_stack_union); -- 2.19.1
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