带有pcap初始化的Valgrind错误

Question

我正在尝试在FreeBSD上使用Valgrind并遇到一些问题。这是输出

==4764== Memcheck, a memory error detector
==4764== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==4764== Using Valgrind-3.8.0 and LibVEX; rerun with -h for copyright info
==4764== Command: driver -i
==4764== 
==4764== 
==4764== HEAP SUMMARY:
==4764==     in use at exit: 33,852 bytes in 4 blocks
==4764==   total heap usage: 12 allocs, 8 frees, 171,894 bytes allocated
==4764== 
==4764== LEAK SUMMARY:
==4764==    definitely lost: 0 bytes in 0 blocks
==4764==    indirectly lost: 0 bytes in 0 blocks
==4764==      possibly lost: 0 bytes in 0 blocks
==4764==    still reachable: 33,852 bytes in 4 blocks
==4764==         suppressed: 0 bytes in 0 blocks
==4764== Rerun with --leak-check=full to see details of leaked memory
==4764== 
==4764== For counts of detected and suppressed errors, rerun with: -v
==4764== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
==4765== Syscall param ioctl(generic) points to uninitialised byte(s)
==4765==    at 0x3196CBC: __sys_ioctl (in /lib/libc.so.7)
==4765==    by 0x1A40469: ??? (in /lib/libpcap.so.8)
==4765==    by 0x1A3ED18: pcap_activate (in /lib/libpcap.so.8)
==4765==    by 0x1A3F43A: pcap_open_live (in /lib/libpcap.so.8)
==4765==    by 0x1822DB7: pcap_init (pcaputil.c:77)
==4765==    by 0x120FE6A: driver_init (recfm.c:387)
==4765==    by 0x402633: main (driver.c:224)
==4765==  Address 0x7ff000270 is on thread 1's stack
==4765==  Uninitialised value was created by a stack allocation
==4765==    at 0x1A3FED0: ??? (in /lib/libpcap.so.8)
==4765== 
==4765== Conditional jump or move depends on uninitialised value(s)
==4765==    at 0x1A408DD: ??? (in /lib/libpcap.so.8)
==4765==    by 0x1A3ED18: pcap_activate (in /lib/libpcap.so.8)
==4765==    by 0x1A3F43A: pcap_open_live (in /lib/libpcap.so.8)
==4765==    by 0x1822DB7: pcap_init (pcaputil.c:77)
==4765==    by 0x120FE6A: driver_init (recfm.c:387)
==4765==    by 0x402633: main (driver.c:224)
==4765==  Uninitialised value was created by a heap allocation
==4765==    at 0x1008DAB: malloc (vg_replace_malloc.c:274)
==4765==    by 0x1A4013E: ??? (in /lib/libpcap.so.8)
==4765==    by 0x1A3ED18: pcap_activate (in /lib/libpcap.so.8)
==4765==    by 0x1A3F43A: pcap_open_live (in /lib/libpcap.so.8)
==4765==    by 0x1822DB7: pcap_init (pcaputil.c:77)
==4765==    by 0x120FE6A: driver_init (recfm.c:387)
==4765==    by 0x402633: main (driver.c:224)
==4765== 
==4765== Warning: noted but unhandled ioctl 0x20004269 with no size/direction hints   This could cause spurious value errors to appear.   See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.Syscall param ioctl(generic) points to uninitialised byte(s)
==4765==    at 0x3196CBC: __sys_ioctl (in /lib/libc.so.7)
==4765==    by 0x1A40291: ??? (in /lib/libpcap.so.8)
==4765==    by 0x1A3ED18: pcap_activate (in /lib/libpcap.so.8)
==4765==    by 0x1A3F43A: pcap_open_live (in /lib/libpcap.so.8)
==4765==    by 0x1822DB7: pcap_init (pcaputil.c:77)
==4765==    by 0x120FE6A: driver_init (recfm.c:387)
==4765==    by 0x402633: main (driver.c:224)
==4765==  Address 0x7fefffd14 is on thread 1's stack
==4765==  Uninitialised value was created by a stack allocation
==4765==    at 0x1A3FEF8: ??? (in /lib/libpcap.so.8)
==4765== 
==4765== Syscall param ioctl(generic) points to uninitialised byte(s)
==4765==    at 0x3196CBC: __sys_ioctl (in /lib/libc.so.7)
==4765==    by 0x1A40C98: ??? (in /lib/libpcap.so.8)
==4765==    by 0x1823277: pcap_init (pcaputil.c:98)
==4765==    by 0x120FE6A: driver_init (recfm.c:387)
==4765==    by 0x402633: main (driver.c:224)
==4765==  Address 0x7ff000454 is on thread 1's stack
==4765==  Uninitialised value was created by a stack allocation
==4765==    at 0x1822C10: pcap_init (pcaputil.c:61)
==4765== 
--4765-- WARNING: unhandled syscall: 522
--4765-- You may be able to write your own handler.
--4765-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
--4765-- Nevertheless we consider this a bug.  Please report
--4765-- it at http://valgrind.org/support/bug_reports.html.

...repeated a bunch of times

最后一次警告反复出现，但是我认为这不一定是问题，对吗？我认为，另一个问题是更多的关注。

看来我的程序仍在后台运行，但是我显然没有从valgrind获得良好的报告。它提到的令人反感的内容之一是pcaputil：77

以下是：

pd=pcap_open_live(__intf, snaplen, 1, 512, ebuf)

其中_intf是char *，snaplen是int，并且ebuf是char ebuf[SIZE] = {0};数组

Answer 1

实际上，这只是Valgrind-for-FreeBSD并没有真正理解一些ioctl。在OS X上存在相同的问题（并且可能在所有其他* BSD上也存在）；参见Valgrind bug 312989（他们使用KDE的错误数据库；实际上并没有超过300,000个错误：-））。

FreeBSD的修复程序将是相似的，尽管出于某种原因，他们决定采用Linux约定“将所有内容从包含文件复制到Valgrind源中”，而不是Darwin约定“仅包含系统标头”文件”；这意味着头文件需要做更多的工作。我会问一下FreeBSD Valgrind的维护者，达尔文的方法是否会更好。

Answer 2

嗯，Valgrind有一个错误。 FreeBSD中有一个系统调用，它无法处理。 pcap可能调用了某些东西。这有可能正在传播，并导致Valgrind认为pcap在未初始化的数据上跳跃。甚至有可能您的程序运行正常，只是Valgrind存在问题。最好的方法是添加您自己的ioctl包装器，对valgrind进行补丁，然后查看它是否仍然怪异。或者，您可以使用pcap的替代方法，它不使用它正在使用的任何系统调用。

抱歉，如果这不是一个简单的解决方案。