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Diffstat (limited to 'results/classifier/semantic-bugs/2371')
| -rw-r--r-- | results/classifier/semantic-bugs/2371 | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/results/classifier/semantic-bugs/2371 b/results/classifier/semantic-bugs/2371 new file mode 100644 index 000000000..2db65ca18 --- /dev/null +++ b/results/classifier/semantic-bugs/2371 @@ -0,0 +1,65 @@ +other: 0.840 +semantic: 0.839 +graphic: 0.831 +mistranslation: 0.816 +vnc: 0.770 +socket: 0.722 +network: 0.699 +instruction: 0.679 +device: 0.671 +assembly: 0.628 +boot: 0.550 +KVM: 0.531 + +A bug in RISC-V froundnx.h instruction +Description of problem: +According to the RISCV ISA manual, the froundnx.h instruction rounds a half-precision floating-point number in the source register to an integer and writes the integer, represented as a half-precision floating-point number, to the destination register. Because the values are stored in 64-bit width registers, they must be NaN-unboxed/boxed before/after the operation. When an input value lacks the proper form of NaN-boxing, it should be treated as a canonical NaN. +However, when an incorrectly NaN-boxed value is passed to froundnx.h, QEMU produces 0 instead of the canonical NaN. This is because there is a typo in the definition of helper_froundnx_h: +``` +// target/riscv/fpu_helper.c +uint64_t helper_froundnx_h(CPURISCVState *env, uint64_t rs1) +{ + float16 frs1 = check_nanbox_s(env, rs1); // This should be check_nanbox_h. + frs1 = float16_round_to_int(frs1, &env->fp_status); + return nanbox_h(env, frs1); +} +``` +Steps to reproduce: +1. Write `test.c`. +``` +#include <stdio.h> + +char i_F6[8] = { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 }; +char o_F5[8]; + +void __attribute__ ((noinline)) show_state() { + for (int i = 0; i < 8; i++) { + printf("%02x ", o_F5[i]); + } + printf("\n"); +} + +void __attribute__ ((noinline)) run() { + __asm__ ( + "lui t5, %hi(i_F6)\n" + "addi t5, t5, %lo(i_F6)\n" + "fld ft6, 0(t5)\n" + ".insn 0x445372d3\n" // froundnx.h ft5, ft6 + "lui t5, %hi(o_F5)\n" + "addi t5, t5, %lo(o_F5)\n" + "fsd ft5, 0(t5)\n" + ); +} + +int main(int argc, char **argv) { + run(); + show_state(); + + return 0; +} +``` +2. Compile `test.bin` using this command: `riscv64-linux-gnu-gcc-12 -O2 -no-pie -march=rv64iv ./test.c -o ./test.bin`. +3. Run QEMU using this command: `qemu-riscv64 -L /usr/riscv64-linux-gnu/ ./test.bin`. +4. The program, runs on top of the buggy QEMU, prints `00 00 ff ff ff ff ff ff`. It should print `00 7e ff ff ff ff ff ff` after the bug is fixed. +Additional information: + |