From: Rafael Ávila de Espíndola <rafael@xxxxxxxxxx> [ 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@xxxxxxxxxxx>. Reported-by: Dmitry Golovin <dima@xxxxxxxxxx> Signed-off-by: Rafael Ávila de Espíndola <rafael@xxxxxxxxxx> [ Update commit message per Boris' and Michael's suggestions. ] Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> [ Massage commit message more, fix typos. ] Signed-off-by: Borislav Petkov <bp@xxxxxxx> Tested-by: Dmitry Golovin <dima@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Brijesh Singh <brijesh.singh@xxxxxxx> Cc: Cao Jin <caoj.fnst@xxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Joerg Roedel <jroedel@xxxxxxx> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tri Vo <trong@xxxxxxxxxxx> Cc: dima@xxxxxxxxxx Cc: morbo@xxxxxxxxxx Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20181219190145.252035-1-ndesaulniers@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 a703842b54de..17e1e60b6b40 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -365,7 +365,7 @@ 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
