aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
-rw-r--r--include/linux/percpu-defs.h65
-rw-r--r--lib/Kconfig.debug15
2 files changed, 71 insertions, 9 deletions
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index 8f921d74f49f..cf32838ad0fa 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -10,21 +10,68 @@
10/* 10/*
11 * Base implementations of per-CPU variable declarations and definitions, where 11 * Base implementations of per-CPU variable declarations and definitions, where
12 * the section in which the variable is to be placed is provided by the 12 * the section in which the variable is to be placed is provided by the
13 * 'section' argument. This may be used to affect the parameters governing the 13 * 'sec' argument. This may be used to affect the parameters governing the
14 * variable's storage. 14 * variable's storage.
15 * 15 *
16 * NOTE! The sections for the DECLARE and for the DEFINE must match, lest 16 * NOTE! The sections for the DECLARE and for the DEFINE must match, lest
17 * linkage errors occur due the compiler generating the wrong code to access 17 * linkage errors occur due the compiler generating the wrong code to access
18 * that section. 18 * that section.
19 */ 19 */
20#define DECLARE_PER_CPU_SECTION(type, name, section) \ 20#define __PCPU_ATTRS(sec) \
21 extern \ 21 __attribute__((section(PER_CPU_BASE_SECTION sec))) \
22 __attribute__((__section__(PER_CPU_BASE_SECTION section))) \ 22 PER_CPU_ATTRIBUTES
23 PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name 23
24 24#define __PCPU_DUMMY_ATTRS \
25#define DEFINE_PER_CPU_SECTION(type, name, section) \ 25 __attribute__((section(".discard"), unused))
26 __attribute__((__section__(PER_CPU_BASE_SECTION section))) \ 26
27 PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name 27/*
28 * s390 and alpha modules require percpu variables to be defined as
29 * weak to force the compiler to generate GOT based external
30 * references for them. This is necessary because percpu sections
31 * will be located outside of the usually addressable area.
32 *
33 * This definition puts the following two extra restrictions when
34 * defining percpu variables.
35 *
36 * 1. The symbol must be globally unique, even the static ones.
37 * 2. Static percpu variables cannot be defined inside a function.
38 *
39 * Archs which need weak percpu definitions should define
40 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
41 *
42 * To ensure that the generic code observes the above two
43 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
44 * definition is used for all cases.
45 */
46#if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
47/*
48 * __pcpu_scope_* dummy variable is used to enforce scope. It
49 * receives the static modifier when it's used in front of
50 * DEFINE_PER_CPU() and will trigger build failure if
51 * DECLARE_PER_CPU() is used for the same variable.
52 *
53 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
54 * such that hidden weak symbol collision, which will cause unrelated
55 * variables to share the same address, can be detected during build.
56 */
57#define DECLARE_PER_CPU_SECTION(type, name, sec) \
58 extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
59 extern __PCPU_ATTRS(sec) __weak __typeof__(type) per_cpu__##name
60
61#define DEFINE_PER_CPU_SECTION(type, name, sec) \
62 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
63 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
64 __PCPU_ATTRS(sec) __weak __typeof__(type) per_cpu__##name
65#else
66/*
67 * Normal declaration and definition macros.
68 */
69#define DECLARE_PER_CPU_SECTION(type, name, sec) \
70 extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
71
72#define DEFINE_PER_CPU_SECTION(type, name, sec) \
73 __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
74#endif
28 75
29/* 76/*
30 * Variant on the per-CPU variable declaration/definition theme used for 77 * Variant on the per-CPU variable declaration/definition theme used for
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 23067ab1a73c..77e0d8b1b7c5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -777,6 +777,21 @@ config DEBUG_BLOCK_EXT_DEVT
777 777
778 Say N if you are unsure. 778 Say N if you are unsure.
779 779
780config DEBUG_FORCE_WEAK_PER_CPU
781 bool "Force weak per-cpu definitions"
782 depends on DEBUG_KERNEL
783 help
784 s390 and alpha require percpu variables in modules to be
785 defined weak to work around addressing range issue which
786 puts the following two restrictions on percpu variable
787 definitions.
788
789 1. percpu symbols must be unique whether static or not
790 2. percpu variables can't be defined inside a function
791
792 To ensure that generic code follows the above rules, this
793 option forces all percpu variables to be defined as weak.
794
780config LKDTM 795config LKDTM
781 tristate "Linux Kernel Dump Test Tool Module" 796 tristate "Linux Kernel Dump Test Tool Module"
782 depends on DEBUG_KERNEL 797 depends on DEBUG_KERNEL