glagolig/heapwatch

heapwatch's Issues

Invalid index

Program terminated with signal SIGSEGV, Segmentation fault.
194 entry = entriesByDataHash[stackHash];
(gdb) bt
#0 0xb778225d in ReferenceStack () at StackStorage.c:194
#1 0xb778179d in malloc (size=size@entry=352) at Preload.c:218
#2 0xb75e985c in __fopen_internal (filename=filename@entry=0xb77561a7 "/proc/filesystems", mode=mode@entry=0xb7756018 "r", is32=is32@entry=0) at iofopen.c:73
#3 0xb75ebe5b in _IO_fopen64 (filename=0xb77561a7 "/proc/filesystems", mode=0xb7756018 "r") at iofopen64.c:39
#4 0xb774a9b2 in selinuxfs_exists () from /lib/i386-linux-gnu/libselinux.so.1
#5 0xb77428c3 in ?? () from /lib/i386-linux-gnu/libselinux.so.1
#6 0xb7799d77 in call_init (l=, argc=argc@entry=2, argv=argv@entry=0xbffd84d4, env=env@entry=0xbffd84e0) at dl-init.c:78
#7 0xb7799e64 in call_init (env=0xbffd84e0, argv=0xbffd84d4, argc=2, l=) at dl-init.c:36
#8 _dl_init (main_map=0xb77ac938, argc=2, argv=0xbffd84d4, env=0xbffd84e0) at dl-init.c:126
#9 0xb778c10f in _dl_start_user () from /lib/ld-linux.so.2

(gdb) p stackHash
$1 = 4294919899

in a different run, in HashFn:
result = -2552111681634388
STORAGE_SIZE = 1299721
result % STORAGE_SIZE = -539301
(unsigned long)(result % STORAGE_SIZE) = 4294427995

Looks like, for negative values of result in HashFn, values larger than STORAGE_SIZE are possible when the signed values are cast to unsigned.

crash

I was seeing a crash because RealMalloc hadn't been assigned because the Init() constructor wasn't called.

LD_PRELOAD=./heapwatch_32.so ls
Segmentation fault (core dumped)
#0 0x00000000 in ?? ()
#1 0xb7737792 in malloc (size=size@entry=352) at Preload.c:216
#2 0xb759f85c in __fopen_internal (filename=filename@entry=0xb770c1a7 "/proc/filesystems", mode=mode@entry=0xb770c018 "r", is32=is32@entry=0) at iofopen.c:73
#3 0xb75a1e5b in _IO_fopen64 (filename=0xb770c1a7 "/proc/filesystems", mode=0xb770c018 "r") at iofopen64.c:39
#4 0xb77009b2 in selinuxfs_exists () from /lib/i386-linux-gnu/libselinux.so.1
#5 0xb76f88c3 in ?? () from /lib/i386-linux-gnu/libselinux.so.1
#6 0xb774fd77 in call_init (l=, argc=argc@entry=2, argv=argv@entry=0xbffbbd14, env=env@entry=0xbffbbd20) at dl-init.c:78
#7 0xb774fe64 in call_init (env=0xbffbbd20, argv=0xbffbbd14, argc=2, l=) at dl-init.c:36
#8 _dl_init (main_map=0xb7762938, argc=2, argv=0xbffbbd14, env=0xbffbbd20) at dl-init.c:126
#9 0xb774210f in _dl_start_user () from /lib/ld-linux.so.2

Instead of using the attribute((constructor)), I changed Init() to be called on first use of malloc. Obviously, this doesn't help if malloc isn't the first function called (i.e., calloc, valloc, posix_memalign are called before Init() is called)