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@kosaki kosaki/memcpy_chk.c
Last active Dec 16, 2015

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% make
cc -D_FORTIFY_SOURCE=2 -Wall -g -O2 memcpy_test.c memcpy_chk.c -o memcpy_test
In function ‘my_memcpy’,
inlined from ‘main’ at memcpy_test.c:29:
memcpy_test.c:17: 警告: call to ‘my_memcpy_warn’ declared with attribute warning: my warning
% ./memcpy_test
my buffer overflow detection
[1] 27873 abort (core dumped) ./memcpy_test
#include <stddef.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
void* my_memcpy_chk (void *dest, const void *src, size_t len, size_t destlen)
{
size_t i;
const char *s = src;
char *d = dest;
if (len > destlen) {
fprintf(stderr, "my buffer overflow detection\n");
abort();
}
for (i=0; i<len; i++)
d[i] = s[i];
return dest;
}
char* my_memcpy_warn () __attribute__ ((alias("my_memcpy_chk")));
#include <string.h>
#include <stdio.h>
char* my_memcpy_chk (char *dest, const char *src, size_t len, size_t destlen);
char* my_memcpy_warn (char *dest, const char *src, size_t len, size_t destlen)
__attribute__((__warning__ ("my warning")));
static char* my_memcpy(char* dst, const char* src, size_t len) __attribute__((always_inline));
static char* my_memcpy(char* dst, const char* src, size_t len)
{
size_t d = __builtin_object_size(dst, 0);
if (d != (size_t) -1) {
if (__builtin_constant_p(len) && len > d)
return my_memcpy_warn(dst, src, len, d);
else
return my_memcpy_chk(dst, src, len, d);
} else
return memcpy (dst, src, len);
}
int main(void)
{
const char *str = "12345";
char buf[5];
my_memcpy(buf, str, strlen(str)+1);
return 0;
}
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