From 3ac6cffea4aa18007a454a7442da2855882f403d Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 30 Jan 2009 16:32:22 +0900 Subject: [PATCH] linker script: use separate simpler definition for PERCPU() Impact: fix linker screwup on x86_32 Recent x86_64 zerobased patches introduced PERCPU_VADDR() to put .data.percpu to a predefined address and re-defined PERCPU() in terms of it. The new macro defined one extra symbol, __per_cpu_load, for LMA of the section so that the init data could be accessed. This new symbol introduced the following problems to x86_32. 1. If __per_cpu_load is defined outside of .data.percpu as an absolute symbol, relocation generation for relocatable kernel fails due to absolute relocation. 2. If __per_cpu_load is put inside .data.percpu with absolute address assignment to work around #1, linker gets confused and under certain configurations ends up relocating the symbol against .data.percpu such that the load address gets added on top of already set load address. As x86_32 doesn't use predefined address for .data.percpu, there's no need for it to care about the possibility of __per_cpu_load being different from __per_cpu_start. This patch defines PERCPU() separately so that __per_cpu_load is defined inside .data.percpu so that everything is ordinary linking-wise. Signed-off-by: Tejun Heo Signed-off-by: Ingo Molnar --- include/asm-generic/vmlinux.lds.h | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 53e21f36a802..5406e70aba86 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -445,10 +445,9 @@ * section in the linker script will go there too. @phdr should have * a leading colon. * - * This macro defines three symbols, __per_cpu_load, __per_cpu_start - * and __per_cpu_end. The first one is the vaddr of loaded percpu - * init data. __per_cpu_start equals @vaddr and __per_cpu_end is the - * end offset. + * Note that this macros defines __per_cpu_load as an absolute symbol. + * If there is no need to put the percpu section at a predetermined + * address, use PERCPU(). */ #define PERCPU_VADDR(vaddr, phdr) \ VMLINUX_SYMBOL(__per_cpu_load) = .; \ @@ -470,7 +469,20 @@ * Align to @align and outputs output section for percpu area. This * macro doesn't maniuplate @vaddr or @phdr and __per_cpu_load and * __per_cpu_start will be identical. + * + * This macro is equivalent to ALIGN(align); PERCPU_VADDR( , ) except + * that __per_cpu_load is defined as a relative symbol against + * .data.percpu which is required for relocatable x86_32 + * configuration. */ #define PERCPU(align) \ . = ALIGN(align); \ - PERCPU_VADDR( , ) + .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { \ + VMLINUX_SYMBOL(__per_cpu_load) = .; \ + VMLINUX_SYMBOL(__per_cpu_start) = .; \ + *(.data.percpu.first) \ + *(.data.percpu.page_aligned) \ + *(.data.percpu) \ + *(.data.percpu.shared_aligned) \ + VMLINUX_SYMBOL(__per_cpu_end) = .; \ + }