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authorChristian Krinitsin <mail@krinitsin.com>2025-07-03 19:39:53 +0200
committerChristian Krinitsin <mail@krinitsin.com>2025-07-03 19:39:53 +0200
commitdee4dcba78baf712cab403d47d9db319ab7f95d6 (patch)
tree418478faf06786701a56268672f73d6b0b4eb239 /results/classifier/108/debug/2495
parent4d9e26c0333abd39bdbd039dcdb30ed429c475ba (diff)
downloademulator-bug-study-dee4dcba78baf712cab403d47d9db319ab7f95d6.tar.gz
emulator-bug-study-dee4dcba78baf712cab403d47d9db319ab7f95d6.zip
restructure results
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@@ -1,87 +0,0 @@
-debug: 0.948
-graphic: 0.934
-PID: 0.928
-other: 0.924
-files: 0.918
-device: 0.916
-performance: 0.890
-socket: 0.881
-vnc: 0.880
-network: 0.858
-boot: 0.856
-KVM: 0.817
-permissions: 0.815
-semantic: 0.809
-
-A bug in x86-64 MMX instructions
-Description of problem:
-It seems QEMU emits invalid TCG when lifting MMX instructions with redundant REX prefixes. For example, when lifting `490f7ec0 (movq r8, mm0)`, QEMU generates the following valid TCG.
-
-```
- ---- 00000000004011f2 0000000000000000
- call enter_mmx,$0x0,$0,env
- ld_i64 loc0,env,$0x270
- mov_i64 r8,loc0
- mov_i64 rip,$0x4011f6
- exit_tb $0x0
- set_label $L0
- exit_tb $0x7f84f82ec143
-```
-
-However, after changing the value of the rex prefix to `4f` , so the instruction becomes `4f0f7ec0 (rex.WRXB movq r8, mm0)`, the lifted TCG is changed to:
-
-```
- ---- 00000000004011f2 0000000000000000
- call enter_mmx,$0x0,$0,env
- ld_i64 loc0,env,$0x2f0 // The offset to MM0 is changed
- mov_i64 r8,loc0
- mov_i64 rip,$0x4011f6
- exit_tb $0x0
- set_label $L0
- exit_tb $0x7f98e82ec143
-```
-
-I have observed this bug in numerous MMX instructions. For example, `410fdaff (rex.B pminub mm7, mm7)` is lifted to the wrong TCGs.
-
-It seems this bug looks similar to #2474.
-Steps to reproduce:
-1. Write `test.c` 
-```
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>
-
-uint8_t i_R8[8] = { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 };
-uint8_t i_MM0[8] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
-uint8_t o_R8[8];
-
-void __attribute__ ((noinline)) show_state() {
-    printf("R8: ");
-    for (int i = 0; i < 8; i++) {
-        printf("%02x ", o_R8[i]);
-    }
-    printf("\n");
-}
-
-void __attribute__ ((noinline)) run() {
-    __asm__ (
-        ".intel_syntax noprefix\n"
-        "mov r8, qword ptr [rip + i_R8]\n"
-        "movq mm0, qword ptr [rip + i_MM0]\n"
-        ".byte 0x4f, 0x0f, 0x7e, 0xc0\n"
-        "mov qword ptr [rip + o_R8], r8\n"
-        ".att_syntax\n"
-    );
-}
-
-int main(int argc, char **argv) {
-    run();
-    show_state();
-    return 0;
-}
-```    
-2. Compile `test.bin` using this command: `gcc-12 -O2 -no-pie ./test.c -o ./test.bin`
-3. Run QEMU using this command: `qemu-x86_64 ./test.bin` 
-4. The program, runs on top of the buggy QEMU, prints the value of R8 as `00 00 00 00 00 00 00 00`. It should print `ff ff ff ff ff ff ff ff` after the bug is fixed.
-Additional information:
-