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x86: use linker to offset symbols by __per_cpu_load

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Impact: cleanup and bug fix

Use the linker to create symbols for certain per-cpu variables
that are offset by __per_cpu_load.  This allows the removal of
the runtime fixup of the GDT pointer, which fixes a bug with
resume reported by Jiri Slaby.

Reported-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Acked-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Brian Gerst 2009-02-08 09:58:39 -05:00 committed by Ingo Molnar
parent d3770449d3
commit 2add8e235c
5 changed files with 35 additions and 24 deletions
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22
arch/x86/include/asm/percpu.h
View file

@ -34,6 +34,12 @@
#define PER_CPU_VAR(var) per_cpu__##var
#endif /* SMP */
#ifdef CONFIG_X86_64_SMP
#define INIT_PER_CPU_VAR(var) init_per_cpu__##var
#else
#define INIT_PER_CPU_VAR(var) per_cpu__##var
#endif
#else /* ...!ASSEMBLY */
#include <linux/stringify.h>
@ -45,6 +51,22 @@
#define __percpu_arg(x) "%" #x
#endif
/*
* Initialized pointers to per-cpu variables needed for the boot
* processor need to use these macros to get the proper address
* offset from __per_cpu_load on SMP.
*
* There also must be an entry in vmlinux_64.lds.S
*/
#define DECLARE_INIT_PER_CPU(var) \
extern typeof(per_cpu_var(var)) init_per_cpu_var(var)
#ifdef CONFIG_X86_64_SMP
#define init_per_cpu_var(var) init_per_cpu__##var
#else
#define init_per_cpu_var(var) per_cpu_var(var)
#endif
/* For arch-specific code, we can use direct single-insn ops (they
* don't give an lvalue though). */
extern void __bad_percpu_size(void);

2
arch/x86/include/asm/processor.h
View file

@ -393,6 +393,8 @@ union irq_stack_union {
};
DECLARE_PER_CPU(union irq_stack_union, irq_stack_union);
DECLARE_INIT_PER_CPU(irq_stack_union);
DECLARE_PER_CPU(char *, irq_stack_ptr);
#endif

6
arch/x86/kernel/cpu/common.c
View file

@ -902,12 +902,8 @@ struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };
DEFINE_PER_CPU_FIRST(union irq_stack_union,
irq_stack_union) __aligned(PAGE_SIZE);
#ifdef CONFIG_SMP
DEFINE_PER_CPU(char *, irq_stack_ptr); /* will be set during per cpu init */
#else
DEFINE_PER_CPU(char *, irq_stack_ptr) =
per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;
#endif
init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;
DEFINE_PER_CPU(unsigned long, kernel_stack) =
(unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE;

21
arch/x86/kernel/head_64.S
View file

@ -205,19 +205,6 @@ ENTRY(secondary_startup_64)
pushq $0
popfq
#ifdef CONFIG_SMP
/*
* Fix up static pointers that need __per_cpu_load added. The assembler
* is unable to do this directly. This is only needed for the boot cpu.
* These values are set up with the correct base addresses by C code for
* secondary cpus.
*/
movq initial_gs(%rip), %rax
cmpl $0, per_cpu__cpu_number(%rax)
jne 1f
addq %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
@ -275,11 +262,7 @@ ENTRY(secondary_startup_64)
ENTRY(initial_code)
.quad x86_64_start_kernel
ENTRY(initial_gs)
#ifdef CONFIG_SMP
.quad __per_cpu_load
#else
.quad PER_CPU_VAR(irq_stack_union)
#endif
.quad INIT_PER_CPU_VAR(irq_stack_union)
__FINITDATA
ENTRY(stack_start)
@ -425,7 +408,7 @@ NEXT_PAGE(level2_spare_pgt)
early_gdt_descr:
.word GDT_ENTRIES*8-1
early_gdt_descr_base:
.quad per_cpu__gdt_page
.quad INIT_PER_CPU_VAR(gdt_page)
ENTRY(phys_base)
/* This must match the first entry in level2_kernel_pgt */

8
arch/x86/kernel/vmlinux_64.lds.S
View file

@ -257,6 +257,14 @@ SECTIONS
DWARF_DEBUG
}
/*
* 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 = per_cpu__##x + __per_cpu_load
INIT_PER_CPU(gdt_page);
INIT_PER_CPU(irq_stack_union);
/*
* Build-time check on the image size:
*/