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Diffstat (limited to 'results/classifier/zero-shot-user-mode/instruction/1815024')
| -rw-r--r-- | results/classifier/zero-shot-user-mode/instruction/1815024 | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/results/classifier/zero-shot-user-mode/instruction/1815024 b/results/classifier/zero-shot-user-mode/instruction/1815024 new file mode 100644 index 000000000..3c95bc42b --- /dev/null +++ b/results/classifier/zero-shot-user-mode/instruction/1815024 @@ -0,0 +1,21 @@ +instruction: 0.883 +runtime: 0.068 +syscall: 0.049 + + + +SIGILL on instruction "stck" under qemu-s390x in user mode + +qemu-s390x in user mode crashes with SIGILL (under host architecture x86_64, running Debian unstable) when executing target instruction "stck" ("STORE CLOCK", see https://www-01.ibm.com/support/docview.wss?uid=isg26480faec85f44e2385256d5200627dee&aid=1), which is basically a kind of equivalent of Intel "rdtsc". The same instruction works fine under qemu-s390x in system mode. The bug is reproducible with both the qemu version distributed in Debian unstable and with the latest upstream master (commit 47994e16b1d66411953623e7c0bf0cdcd50bd507). + +This bug manifested itself as a crash of ssh-keygen program, which uses "stck" to obtain some bits of randomness during key creation. Bisection of the code led to the attached minimal example. Compile with (inside an s390x system): + + $ gcc -c -o test.o test.c + $ gcc -c -o rdtsc.o rdtsc.S + $ gcc -o test test.o rdtsc.o + +Then run test. It will crash with SIGILL in user mode and run fine in system mode. Also, compare with the original file at https://github.com/openssl/openssl/blob/master/crypto/s390xcpuid.pl#L139 (there the instruction "stckf" is also used; it is probable that it has the same problem if it is supported altogether, but it did not test for this). + +Running qemu-s390x with options -d in_asm,out_asm,op,op_opt,exec,nochain,cpu gives the trace attached in log.txt. + +Thanks, Giovanni. \ No newline at end of file |