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| author | Tejun Heo <tj@kernel.org> | 2009-01-13 12:41:35 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-01-16 14:19:14 +0100 |
| commit | 3e5d8f978435bb9ba4dfe3f4514e65e7885db1a9 (patch) | |
| tree | 1ce55b2ec16a0bd59a29857e05215960d463a1d8 /arch/x86/kernel/head_64.S | |
| parent | x86: make vmlinux_32.lds.S use PERCPU() macro (diff) | |
| download | linux-3e5d8f978435bb9ba4dfe3f4514e65e7885db1a9.tar.xz linux-3e5d8f978435bb9ba4dfe3f4514e65e7885db1a9.zip | |
x86: make percpu symbols zerobased on SMP
[ 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>
Diffstat (limited to 'arch/x86/kernel/head_64.S')
| -rw-r--r-- | arch/x86/kernel/head_64.S | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 0e275d495563..7ee0363871e8 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -204,6 +204,23 @@ ENTRY(secondary_startup_64) pushq $0 popfq +#ifdef CONFIG_SMP + /* + * early_gdt_base should point to the gdt_page in static percpu init + * data area. Computing this requires two symbols - __per_cpu_load + * and per_cpu__gdt_page. As linker can't do no such relocation, do + * it by hand. As early_gdt_descr is manipulated by C code for + * secondary CPUs, this should be done only once for the boot CPU + * when early_gdt_descr_base contains zero. + */ + movq early_gdt_descr_base(%rip), %rax + testq %rax, %rax + jnz 1f + movq $__per_cpu_load, %rax + addq $per_cpu__gdt_page, %rax + movq %rax, early_gdt_descr_base(%rip) +1: +#endif /* * We must switch to a new descriptor in kernel space for the GDT * because soon the kernel won't have access anymore to the userspace @@ -401,7 +418,12 @@ NEXT_PAGE(level2_spare_pgt) .globl early_gdt_descr early_gdt_descr: .word GDT_ENTRIES*8-1 - .quad per_cpu__gdt_page +#ifdef CONFIG_SMP +early_gdt_descr_base: + .quad 0x0000000000000000 +#else + .quad per_cpu__gdt_page +#endif ENTRY(phys_base) /* This must match the first entry in level2_kernel_pgt */ |