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shared: add helper function to add and check for overflow

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Use _builtin_uaddll_overflow/_builtin_uaddl_overflow when available,
abstracting the type to use it with uint64_t.

Otherwise fallback to the implementation as added in 67466f2 ("Prevent
offset + size overflow.").

This also adds the tests for this new helper in the testsuite.
This commit is contained in:
Lucas De Marchi 2015-02-10 10:41:47 -02:00
parent 14c3244f04
commit aac5f4514f
4 changed files with 39 additions and 0 deletions
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2
configure.ac
View File

@ -49,6 +49,8 @@ AC_CHECK_FUNCS_ONCE([finit_module])
CC_CHECK_FUNC_BUILTIN([__builtin_clz])
CC_CHECK_FUNC_BUILTIN([__builtin_types_compatible_p])
CC_CHECK_FUNC_BUILTIN([__builtin_uaddl_overflow], [ ], [ ])
CC_CHECK_FUNC_BUILTIN([__builtin_uaddll_overflow], [ ], [ ])
# dietlibc doesn't have st.st_mtim struct member
AC_CHECK_MEMBERS([struct stat.st_mtim], [], [], [#include <sys/stat.h>])

2
m4/attributes.m4
View File

@ -262,6 +262,8 @@ AC_DEFUN([CC_CHECK_FUNC_BUILTIN], [
m4_case([$1],
[__builtin_clz], [$1(0)],
[__builtin_types_compatible_p], [$1(int, int)],
[__builtin_uaddl_overflow], [$1(0UL, 0UL, (void*)0)],
[__builtin_uaddll_overflow], [$1(0ULL, 0ULL, (void*)0)],
[__builtin_expect], [$1(0, 0)]
)])],
[cc_cv_have_$1=yes],

16
shared/util.h
View File

@ -1,5 +1,6 @@
#pragma once
#include <inttypes.h>
#include <limits.h>
#include <stdbool.h>
#include <stdlib.h>
@ -72,3 +73,18 @@ static inline void freep(void *p) {
free(*(void**) p);
}
#define _cleanup_free_ _cleanup_(freep)
static inline bool addu64_overflow(uint64_t a, uint64_t b, uint64_t *res)
{
#if (HAVE___BUILTIN_UADDL_OVERFLOW && HAVE___BUILTIN_UADDLL_OVERFLOW)
#if __SIZEOF_LONG__ == 8
return __builtin_uaddl_overflow(a, b, res);
#elif __SIZEOF_LONG_LONG__ == 8
return __builtin_uaddll_overflow(a, b, res);
#else
#error "sizeof(long long) != 8"
#endif
#endif
*res = a + b;
return ULLONG_MAX - a < b;
}

19
testsuite/test-util.c
View File

@ -206,5 +206,24 @@ DEFINE_TEST(test_write_str_safe,
},
});
static int test_addu64_overflow(const struct test *t)
{
uint64_t res;
bool overflow;
overflow = addu64_overflow(UINT64_MAX - 1, 1, &res);
assert_return(!overflow, EXIT_FAILURE);
assert_return(res == UINT64_MAX, EXIT_FAILURE);
overflow = addu64_overflow(UINT64_MAX, 1, &res);
assert_return(overflow, EXIT_FAILURE);
return EXIT_SUCCESS;
}
DEFINE_TEST(test_addu64_overflow,
.description = "check implementation of addu4_overflow()",
.need_spawn = false,
);
TESTSUITE_MAIN();