[patch 2/3] add new macros to make percpu readmostly sectioncorrectly align

From: Shaohua Li
Date: Wed Dec 01 2010 - 21:03:34 EST


percpu readmostly section should start and end at address cachline aligned.
Idealy we should change PERCPU_VADDR/PERCPU, but I can't change all arch code, so
I add new macros for x86.

Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>

---
include/asm-generic/vmlinux.lds.h | 66 ++++++++++++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)

Index: linux/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux.orig/include/asm-generic/vmlinux.lds.h 2010-12-02 09:22:32.000000000 +0800
+++ linux/include/asm-generic/vmlinux.lds.h 2010-12-02 09:32:42.000000000 +0800
@@ -726,6 +726,72 @@
VMLINUX_SYMBOL(__per_cpu_end) = .; \
}

+/**
+ * PERCPU_VADDR_CACHEALIGNED - define output section for percpu area
+ * @vaddr: explicit base address (optional)
+ * @phdr: destination PHDR (optional)
+ * @cacheline: cachline size required by readmostly percpu data
+ *
+ * Macro which expands to output section for percpu area. If @vaddr
+ * is not blank, it specifies explicit base address and all percpu
+ * symbols will be offset from the given address. If blank, @vaddr
+ * always equals @laddr + LOAD_OFFSET.
+ *
+ * @phdr defines the output PHDR to use if not blank. Be warned that
+ * output PHDR is sticky. If @phdr is specified, the next output
+ * section in the linker script will go there too. @phdr should have
+ * a leading colon.
+ *
+ * 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_CACHEALIGNED().
+ */
+#define PERCPU_VADDR_CACHEALIGNED(vaddr, phdr, cacheline) \
+ VMLINUX_SYMBOL(__per_cpu_load) = .; \
+ .data..percpu vaddr : AT(VMLINUX_SYMBOL(__per_cpu_load) \
+ - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__per_cpu_start) = .; \
+ *(.data..percpu..first) \
+ . = ALIGN(PAGE_SIZE); \
+ *(.data..percpu..page_aligned) \
+ . = ALIGN(cacheline); \
+ *(.data..percpu..readmostly) \
+ . = ALIGN(cacheline); \
+ *(.data..percpu) \
+ *(.data..percpu..shared_aligned) \
+ VMLINUX_SYMBOL(__per_cpu_end) = .; \
+ } phdr \
+ . = VMLINUX_SYMBOL(__per_cpu_load) + SIZEOF(.data..percpu);
+
+/**
+ * PERCPU_CACHEALIGNED - define output section for percpu area, simple version
+ * @align: required alignment
+ * @cacheline: cachline size required by readmostly percpu data
+ *
+ * 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_CACHEALIGNED( , ) except
+ * that __per_cpu_load is defined as a relative symbol against
+ * .data..percpu which is required for relocatable x86_32
+ * configuration.
+ */
+#define PERCPU_CACHEALIGNED(align, cacheline) \
+ . = ALIGN(align); \
+ .data..percpu : AT(ADDR(.data..percpu) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__per_cpu_load) = .; \
+ VMLINUX_SYMBOL(__per_cpu_start) = .; \
+ *(.data..percpu..first) \
+ . = ALIGN(PAGE_SIZE); \
+ *(.data..percpu..page_aligned) \
+ . = ALIGN(cacheline); \
+ *(.data..percpu..readmostly) \
+ . = ALIGN(cacheline); \
+ *(.data..percpu) \
+ *(.data..percpu..shared_aligned) \
+ VMLINUX_SYMBOL(__per_cpu_end) = .; \
+ }

/*
* Definition of the high level *_SECTION macros


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