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x86: make percpu symbols zerobased on SMP

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[ Based on original patch from Christoph Lameter and Mike Travis. ]

This patch makes percpu symbols zerobased on x86_64 SMP by adding
PERCPU_VADDR() to vmlinux.lds.h which helps setting explicit vaddr on
the percpu output section and using it in vmlinux_64.lds.S.  A new
PHDR is added as existing ones cannot contain sections near address
zero.  PERCPU_VADDR() also adds a new symbol __per_cpu_load which
always points to the vaddr of the loaded percpu data.init region.

The following adjustments have been made to accomodate the address
change.

* code to locate percpu gdt_page in head_64.S is updated to add the
  load address to the gdt_page offset.

* __per_cpu_load is used in places where access to the init data area
  is necessary.

* pda->data_offset is initialized soon after C code is entered as zero
  value doesn't work anymore.

This patch is mostly taken from Mike Travis' "x86_64: Base percpu
variables at zero" patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Tejun Heo
2009-01-16 14:19:14 +01:00
committed by Ingo Molnar
parent a698c823e1
commit 3e5d8f9784
6 changed files with 88 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/asm-generic/sections.h
+1 -1
View File
@@ -9,7 +9,7 @@ extern char __bss_start[], __bss_stop[];
extern char __init_begin[], __init_end[];
extern char _sinittext[], _einittext[];
extern char _end[];
extern char __per_cpu_start[], __per_cpu_end[];
extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __start_rodata[], __end_rodata[];
include/asm-generic/vmlinux.lds.h
+45 -6
View File
@@ -430,12 +430,51 @@
*(.initcall7.init) \
*(.initcall7s.init)
#define PERCPU(align) \
. = ALIGN(align); \
VMLINUX_SYMBOL(__per_cpu_start) = .; \
.data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { \
#define PERCPU_PROLOG(vaddr) \
VMLINUX_SYMBOL(__per_cpu_load) = .; \
.data.percpu vaddr : AT(__per_cpu_load - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__per_cpu_start) = .;
#define PERCPU_EPILOG(phdr) \
VMLINUX_SYMBOL(__per_cpu_end) = .; \
} phdr \
. = __per_cpu_load + SIZEOF(.data.percpu);
/**
* PERCPU_VADDR - define output section for percpu area
* @vaddr: explicit base address (optional)
* @phdr: destination PHDR (optional)
*
* 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.
*
* 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.
*/
#define PERCPU_VADDR(vaddr, phdr) \
PERCPU_PROLOG(vaddr) \
*(.data.percpu.page_aligned) \
*(.data.percpu) \
*(.data.percpu.shared_aligned) \
} \
VMLINUX_SYMBOL(__per_cpu_end) = .;
PERCPU_EPILOG(phdr)
/**
* PERCPU - define output section for percpu area, simple version
* @align: required alignment
*
* 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.
*/
#define PERCPU(align) \
. = ALIGN(align); \
PERCPU_VADDR( , )