Two changes:
1) Detect memory read overruns.
For example:
int main() {
char buf[10];
memcpy(buf, "abcde", sizeof(buf));
sprintf("%s\n", buf);
}
because "abcde" is only 6 bytes, copying 10 bytes from it is a bug.
This particular bug will be detected at compile time. Other similar
bugs may be detected at runtime.
2) Detect overlapping buffers on memcpy()
It is a bug to call memcpy() on buffers which overlap. For
example, the following code is buggy:
char buf3[0x800];
char *first_half = &buf3[0x400];
char *second_half = &buf3[1];
memset(buf3, 0, sizeof(buf3));
memcpy(first_half, second_half, 0x400);
printf("1: %s\n", buf3);
We now detect this at compile and run time.
Change-Id: I092bd89f11f18e08e8a9dda0ca903aaea8e06d91
memmove() unconditionally calls memcpy() if "dst" < "src". For
example, in the code below, memmove() would end up calling memcpy(),
even though the regions of memory overlap.
int main() {
char buf3[0x800];
char *dst = &buf3[1];
char *src = &buf3[0x400];
memset(buf3, 0, sizeof(buf3));
memmove(dst, src, 0x400);
printf("1: %s\n", buf3);
return 0;
}
Calling memcpy() on overlaping regions only works if you assume
that memcpy() copies from start to finish. On some architectures,
it's more efficient to call memcpy() from finish to start.
This is also triggering a failure in some of my code.
More reading:
* http://lwn.net/Articles/414467/
* https://bugzilla.redhat.com/show_bug.cgi?id=638477#c31 (comment 31)
Change-Id: I65a51ae3a52dd4af335fe5c278056b8c2cbd8948
On ARM there is currently no assembler optimized memmove in libc.
There is however a more optimized bcopy which copies long instead
of bytes where possible. This almost doubles the performance in
best case.
Change-Id: I1f1cd27529443358047c385730deaf938ce4e642
This reverts commit 80fba9a2fe,
which caused the system to not boot anymore, aborting with:
"java.lang.RuntimeException: Missing static main on com.android.server.SystemServer".
Change-Id: I745e0a23c728cccf5f95a3c7642d544478a4e57e
