tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking/core head: 52fa5bc5cbba089f09bc2c372e3432f3f3e48051 commit: 7a46ec0e2f4850407de5e1d19a44edee6efa58ec [36/40] locking/refcounts, x86/asm: Implement fast refcount overflow protection config: i386-tinyconfig (attached as .config) compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901 reproduce: git checkout 7a46ec0e2f4850407de5e1d19a44edee6efa58ec # save the attached .config to linux build tree make ARCH=i386
All error/warnings (new ones prefixed by >>):
In file included from include/linux/refcount.h:57:0,
from include/linux/kref.h:19,
from include/linux/kobject.h:24,
from include/linux/irqdesc.h:5,
from include/linux/irq.h:495,
from arch/x86/include/asm/hardirq.h:5,
from include/linux/hardirq.h:8,
from arch/x86/kernel/asm-offsets.c:11:
arch/x86/include/asm/refcount.h: In function 'refcount_add':
>> arch/x86/include/asm/refcount.h:21:2: error: expected ':' or ')' before
>> 'ASM_UNREACHABLE'
ASM_UNREACHABLE \
^
>> arch/x86/include/asm/refcount.h:29:2: note: in expansion of macro
>> '_REFCOUNT_EXCEPTION'
_REFCOUNT_EXCEPTION
^~~~~~~~~~~~~~~~~~~
>> arch/x86/include/asm/refcount.h:44:3: note: in expansion of macro
>> 'REFCOUNT_CHECK_LT_ZERO'
REFCOUNT_CHECK_LT_ZERO
^~~~~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h: In function 'refcount_inc':
>> arch/x86/include/asm/refcount.h:21:2: error: expected ':' or ')' before
>> 'ASM_UNREACHABLE'
ASM_UNREACHABLE \
^
>> arch/x86/include/asm/refcount.h:29:2: note: in expansion of macro
>> '_REFCOUNT_EXCEPTION'
_REFCOUNT_EXCEPTION
^~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h:53:3: note: in expansion of macro
'REFCOUNT_CHECK_LT_ZERO'
REFCOUNT_CHECK_LT_ZERO
^~~~~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h: In function 'refcount_dec':
>> arch/x86/include/asm/refcount.h:21:2: error: expected ':' or ')' before
>> 'ASM_UNREACHABLE'
ASM_UNREACHABLE \
^
>> arch/x86/include/asm/refcount.h:29:2: note: in expansion of macro
>> '_REFCOUNT_EXCEPTION'
_REFCOUNT_EXCEPTION
^~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h:34:2: note: in expansion of macro
'REFCOUNT_CHECK_LT_ZERO'
REFCOUNT_CHECK_LT_ZERO
^~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/include/asm/refcount.h:61:3: note: in expansion of macro
>> 'REFCOUNT_CHECK_LE_ZERO'
REFCOUNT_CHECK_LE_ZERO
^~~~~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h: In function 'refcount_sub_and_test':
>> arch/x86/include/asm/refcount.h:69:2: error: implicit declaration of
>> function 'GEN_BINARY_SUFFIXED_RMWcc' [-Werror=implicit-function-declaration]
GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl", REFCOUNT_CHECK_LT_ZERO,
^~~~~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/include/asm/refcount.h:21:2: error: expected ')' before
>> 'ASM_UNREACHABLE'
ASM_UNREACHABLE \
^
>> arch/x86/include/asm/refcount.h:29:2: note: in expansion of macro
>> '_REFCOUNT_EXCEPTION'
_REFCOUNT_EXCEPTION
^~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h:69:48: note: in expansion of macro
'REFCOUNT_CHECK_LT_ZERO'
GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl", REFCOUNT_CHECK_LT_ZERO,
^~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/include/asm/refcount.h:71:1: warning: no return statement in
>> function returning non-void [-Wreturn-type]
}
^
arch/x86/include/asm/refcount.h: In function 'refcount_dec_and_test':
>> arch/x86/include/asm/refcount.h:75:2: error: implicit declaration of
>> function 'GEN_UNARY_SUFFIXED_RMWcc' [-Werror=implicit-function-declaration]
GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl", REFCOUNT_CHECK_LT_ZERO,
^~~~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/include/asm/refcount.h:21:2: error: expected ')' before
>> 'ASM_UNREACHABLE'
ASM_UNREACHABLE \
^
>> arch/x86/include/asm/refcount.h:29:2: note: in expansion of macro
>> '_REFCOUNT_EXCEPTION'
_REFCOUNT_EXCEPTION
^~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h:75:47: note: in expansion of macro
'REFCOUNT_CHECK_LT_ZERO'
GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl", REFCOUNT_CHECK_LT_ZERO,
^~~~~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/refcount.h:77:1: warning: no return statement in
function returning non-void [-Wreturn-type]
}
^
arch/x86/include/asm/refcount.h: In function 'refcount_add_not_zero':
>> arch/x86/include/asm/refcount.h:21:2: error: expected ':' or ')' before
>> 'ASM_UNREACHABLE'
ASM_UNREACHABLE \
^
arch/x86/include/asm/refcount.h:39:2: note: in expansion of macro
'_REFCOUNT_EXCEPTION'
_REFCOUNT_EXCEPTION
^~~~~~~~~~~~~~~~~~~
>> arch/x86/include/asm/refcount.h:93:17: note: in expansion of macro
>> 'REFCOUNT_ERROR'
asm volatile(REFCOUNT_ERROR
^~~~~~~~~~~~~~
cc1: some warnings being treated as errors
make[2]: *** [arch/x86/kernel/asm-offsets.s] Error 1
make[2]: Target '__build' not remade because of errors.
make[1]: *** [prepare0] Error 2
make[1]: Target 'prepare' not remade because of errors.
make: *** [sub-make] Error 2
vim +21 arch/x86/include/asm/refcount.h
8
9 /*
10 * This is the first portion of the refcount error handling, which
lives in
11 * .text.unlikely, and is jumped to from the CPU flag check (in the
12 * following macros). This saves the refcount value location into CX for
13 * the exception handler to use (in mm/extable.c), and then triggers the
14 * central refcount exception. The fixup address for the exception
points
15 * back to the regular execution flow in .text.
16 */
17 #define _REFCOUNT_EXCEPTION \
18 ".pushsection .text.unlikely\n" \
19 "111:\tlea %[counter], %%" _ASM_CX "\n" \
20 "112:\t" ASM_UD0 "\n" \
> 21 ASM_UNREACHABLE \
22 ".popsection\n" \
23 "113:\n" \
24 _ASM_EXTABLE_REFCOUNT(112b, 113b)
25
26 /* Trigger refcount exception if refcount result is negative. */
27 #define REFCOUNT_CHECK_LT_ZERO \
28 "js 111f\n\t" \
> 29 _REFCOUNT_EXCEPTION
30
31 /* Trigger refcount exception if refcount result is zero or negative. */
32 #define REFCOUNT_CHECK_LE_ZERO \
33 "jz 111f\n\t" \
> 34 REFCOUNT_CHECK_LT_ZERO
35
36 /* Trigger refcount exception unconditionally. */
37 #define REFCOUNT_ERROR \
38 "jmp 111f\n\t" \
39 _REFCOUNT_EXCEPTION
40
41 static __always_inline void refcount_add(unsigned int i, refcount_t *r)
42 {
43 asm volatile(LOCK_PREFIX "addl %1,%0\n\t"
> 44 REFCOUNT_CHECK_LT_ZERO
45 : [counter] "+m" (r->refs.counter)
46 : "ir" (i)
47 : "cc", "cx");
48 }
49
50 static __always_inline void refcount_inc(refcount_t *r)
51 {
52 asm volatile(LOCK_PREFIX "incl %0\n\t"
53 REFCOUNT_CHECK_LT_ZERO
54 : [counter] "+m" (r->refs.counter)
55 : : "cc", "cx");
56 }
57
58 static __always_inline void refcount_dec(refcount_t *r)
59 {
60 asm volatile(LOCK_PREFIX "decl %0\n\t"
> 61 REFCOUNT_CHECK_LE_ZERO
62 : [counter] "+m" (r->refs.counter)
63 : : "cc", "cx");
64 }
65
66 static __always_inline __must_check
67 bool refcount_sub_and_test(unsigned int i, refcount_t *r)
68 {
> 69 GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
REFCOUNT_CHECK_LT_ZERO,
70 r->refs.counter, "er", i, "%0", e);
> 71 }
72
73 static __always_inline __must_check bool
refcount_dec_and_test(refcount_t *r)
74 {
> 75 GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
REFCOUNT_CHECK_LT_ZERO,
76 r->refs.counter, "%0", e);
77 }
78
79 static __always_inline __must_check
80 bool refcount_add_not_zero(unsigned int i, refcount_t *r)
81 {
82 int c, result;
83
84 c = atomic_read(&(r->refs));
85 do {
86 if (unlikely(c == 0))
87 return false;
88
89 result = c + i;
90
91 /* Did we try to increment from/to an undesirable
state? */
92 if (unlikely(c < 0 || c == INT_MAX || result < c)) {
> 93 asm volatile(REFCOUNT_ERROR
94 : : [counter] "m" (r->refs.counter)
95 : "cc", "cx");
96 break;
97 }
98
99 } while (!atomic_try_cmpxchg(&(r->refs), &c, result));
100
101 return c != 0;
102 }
103
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