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authorChristian Krinitsin <mail@krinitsin.com>2025-06-01 21:19:28 +0200
committerChristian Krinitsin <mail@krinitsin.com>2025-06-01 21:19:28 +0200
commit05ed9b00104b3da2e9cb0d541b5c5bbceb027fde (patch)
treed47bd9721b78db6131d56780e7230cf69412eaa6 /classification/semantic_issues/gitlab_semantic_addsubps
parentcddf7dfa5a6e92a9057e7f6afae5d9b970585e6f (diff)
downloademulator-bug-study-05ed9b00104b3da2e9cb0d541b5c5bbceb027fde.tar.gz
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+x86 SSE/SSE2/SSE3 instruction semantic bugs with NaN
+
+Description of problem
+The result of SSE/SSE2/SSE3 instructions with NaN is different from the CPU. From Intel manual Volume 1 Appendix D.4.2.2, they defined the behavior of such instructions with NaN. But I think QEMU did not implement this semantic exactly because the byte result is different.
+
+Steps to reproduce
+
+Compile this code
+
+void main() {
+    asm("mov rax, 0x000000007fffffff; push rax; mov rax, 0x00000000ffffffff; push rax; movdqu XMM1, [rsp];");
+    asm("mov rax, 0x2e711de7aa46af1a; push rax; mov rax, 0x7fffffff7fffffff; push rax; movdqu XMM2, [rsp];");
+    asm("addsubps xmm1, xmm2");
+}
+
+Execute and compare the result with the CPU. This problem happens with other SSE/SSE2/SSE3 instructions specified in the manual, Volume 1 Appendix D.4.2.2.
+
+CPU xmm1[3] = 0xffffffff
+
+QEMU xmm1[3] = 0x7fffffff
+
+Additional information
+This bug is discovered by research conducted by KAIST SoftSec.