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authorIvan Kokshaysky <ink@jurassic.park.msu.ru>2008-06-20 19:25:39 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-06-20 19:46:10 -0400
commit9267b4b3880d00dc2dab90f1d817c856939114f7 (patch)
tree9823a76657f257d71aac2a5f4374c56560dd2e6e /include/asm-alpha
parentd70ac829b7f42d7ef4f879635c6a772b0b4ed0a2 (diff)
alpha: fix module load failures on smp (bug #10926)
To calculate addresses of locally defined variables, GCC uses 32-bit displacement from the GP. Which doesn't work for per cpu variables in modules, as an offset to the kernel per cpu area is way above 4G. The workaround is to force allocation of a GOT entry for per cpu variable using ldq instruction with a 'literal' relocation. I had to use custom asm/percpu.h, as a required argument magic doesn't work with asm-generic/percpu.h macros. Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/asm-alpha')
-rw-r--r--include/asm-alpha/percpu.h72
1 files changed, 71 insertions, 1 deletions
diff --git a/include/asm-alpha/percpu.h b/include/asm-alpha/percpu.h
index 48348fe34c19..82e8a94b4b2f 100644
--- a/include/asm-alpha/percpu.h
+++ b/include/asm-alpha/percpu.h
@@ -1,6 +1,76 @@
1#ifndef __ALPHA_PERCPU_H 1#ifndef __ALPHA_PERCPU_H
2#define __ALPHA_PERCPU_H 2#define __ALPHA_PERCPU_H
3#include <linux/compiler.h>
4#include <linux/threads.h>
3 5
4#include <asm-generic/percpu.h> 6/*
7 * Determine the real variable name from the name visible in the
8 * kernel sources.
9 */
10#define per_cpu_var(var) per_cpu__##var
11
12#ifdef CONFIG_SMP
13
14/*
15 * per_cpu_offset() is the offset that has to be added to a
16 * percpu variable to get to the instance for a certain processor.
17 */
18extern unsigned long __per_cpu_offset[NR_CPUS];
19
20#define per_cpu_offset(x) (__per_cpu_offset[x])
21
22#define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
23#ifdef CONFIG_DEBUG_PREEMPT
24#define my_cpu_offset per_cpu_offset(smp_processor_id())
25#else
26#define my_cpu_offset __my_cpu_offset
27#endif
28
29#ifndef MODULE
30#define SHIFT_PERCPU_PTR(var, offset) RELOC_HIDE(&per_cpu_var(var), (offset))
31#define PER_CPU_ATTRIBUTES
32#else
33/*
34 * To calculate addresses of locally defined variables, GCC uses 32-bit
35 * displacement from the GP. Which doesn't work for per cpu variables in
36 * modules, as an offset to the kernel per cpu area is way above 4G.
37 *
38 * This forces allocation of a GOT entry for per cpu variable using
39 * ldq instruction with a 'literal' relocation.
40 */
41#define SHIFT_PERCPU_PTR(var, offset) ({ \
42 extern int simple_identifier_##var(void); \
43 unsigned long __ptr, tmp_gp; \
44 asm ( "br %1, 1f \n\
45 1: ldgp %1, 0(%1) \n\
46 ldq %0, per_cpu__" #var"(%1)\t!literal" \
47 : "=&r"(__ptr), "=&r"(tmp_gp)); \
48 (typeof(&per_cpu_var(var)))(__ptr + (offset)); })
49
50#define PER_CPU_ATTRIBUTES __used
51
52#endif /* MODULE */
53
54/*
55 * A percpu variable may point to a discarded regions. The following are
56 * established ways to produce a usable pointer from the percpu variable
57 * offset.
58 */
59#define per_cpu(var, cpu) \
60 (*SHIFT_PERCPU_PTR(var, per_cpu_offset(cpu)))
61#define __get_cpu_var(var) \
62 (*SHIFT_PERCPU_PTR(var, my_cpu_offset))
63#define __raw_get_cpu_var(var) \
64 (*SHIFT_PERCPU_PTR(var, __my_cpu_offset))
65
66#else /* ! SMP */
67
68#define per_cpu(var, cpu) (*((void)(cpu), &per_cpu_var(var)))
69#define __get_cpu_var(var) per_cpu_var(var)
70#define __raw_get_cpu_var(var) per_cpu_var(var)
71
72#endif /* SMP */
73
74#define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu_var(name)
5 75
6#endif /* __ALPHA_PERCPU_H */ 76#endif /* __ALPHA_PERCPU_H */