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Created attachment 434491 [details] A testcase for Linux/x86-64 On x86-64, there is a 128byte red zone. But valgrind-3.5.0-17.fc13.x86_64 failed to handle it properly: [hjl@gnu-6 valgrind-1]$ make gcc -O2 foo.c -o foo ./foo || true valgrind --tool=memcheck ./foo ==23552== Memcheck, a memory error detector ==23552== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al. ==23552== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info ==23552== Command: ./foo ==23552== ==23552== Invalid read of size 8 ==23552== at 0x400548: check_absence_pattern_sets (in /export/home/hjl/bugs/gcc/valgrind-1/foo) ==23552== by 0x400676: main (in /export/home/hjl/bugs/gcc/valgrind-1/foo) ==23552== Address 0x1c is not stack'd, malloc'd or (recently) free'd ==23552== ==23552== ==23552== Process terminating with default action of signal 11 (SIGSEGV) ==23552== Access not within mapped region at address 0x1C ==23552== at 0x400548: check_absence_pattern_sets (in /export/home/hjl/bugs/gcc/valgrind-1/foo) ==23552== by 0x400676: main (in /export/home/hjl/bugs/gcc/valgrind-1/foo) ==23552== If you believe this happened as a result of a stack ==23552== overflow in your program's main thread (unlikely but ==23552== possible), you can try to increase the size of the ==23552== main thread stack using the --main-stacksize= flag. ==23552== The main thread stack size used in this run was 8388608. ==23552== ==23552== HEAP SUMMARY: ==23552== in use at exit: 96 bytes in 2 blocks ==23552== total heap usage: 2 allocs, 0 frees, 96 bytes allocated ==23552== ==23552== LEAK SUMMARY: ==23552== definitely lost: 0 bytes in 0 blocks ==23552== indirectly lost: 0 bytes in 0 blocks ==23552== possibly lost: 0 bytes in 0 blocks ==23552== still reachable: 96 bytes in 2 blocks ==23552== suppressed: 0 bytes in 0 blocks ==23552== Rerun with --leak-check=full to see details of leaked memory ==23552== ==23552== For counts of detected and suppressed errors, rerun with: -v ==23552== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 6 from 6) make: *** [all] Segmentation fault [hjl@gnu-6 valgrind-1]$
Valgrind will touch (%RSP - 8). If (%RSP - 8) is used for spill, we will get the wrong value when it is restored.
Please continue in the upstream bug.
Created attachment 434800 [details] A smaller testcase Here is a smaller testcase which doesn't require libc. I also fixed a bug in the original testcase.