Gunnar,
As usual, fantastic work. We'll review it for merging and toss it into the
repository.
Thanks,
Tyler
> Hello everybody,
>
> in the master branch, marss/ptlsim/x86/decode-complex.cpp, lines 2048+,
>
> case 0xfa: { // cli
> EndOfDecode();
>
> // this << TransOp(OP_collcc, REG_temp0, REG_zf, REG_cf, REG_of,
> // 3, 0, 0, FLAGS_DEFAULT_ALU);
> TransOp ast(OP_ast, REG_temp1, REG_temp0, REG_zero, REG_zero, 3);
> ast.riptaken = L_ASSIST_CLI;
>
> and lines 2061+,
>
> case 0xfb: { // sti
> EndOfDecode();
>
> // this << TransOp(OP_collcc, REG_temp0, REG_zf, REG_cf, REG_of,
> // 3, 0, 0, FLAGS_DEFAULT_ALU);
> TransOp ast(OP_ast, REG_temp1, REG_temp0, REG_zero, REG_zero, 3);
> ast.riptaken = L_ASSIST_STI;
>
> The lightweight assist functions are called with uninitialized values of
> the ra
> parameter. Lines 231+,
>
> W64 l_assist_sti(Context& ctx, W64 ra, W64 rb, W64 rc, W16 raflags,
> W16 rbflags, W16 rcflags, W16& flags) {
>
> W16 current_flags = (W16)ra;
> current_flags |= IF_MASK;
> flags = current_flags;
>
> and lines 254+,
>
> W64 l_assist_cli(Context& ctx, W64 ra, W64 rb, W64 rc, W16 raflags,
> W16 rbflags, W16 rcflags, W16& flags) {
>
> W16 current_flags = (W16)ra;
> current_flags &= ~IF_MASK;
> flags = current_flags;
>
> Now, the unintialized ra parameter might have FLAG_INV set. This will make
> the
> assist uop fail and can cause indefinite re-issues of this and preceding
> not-yet-committed uops if the uninitialized REG_temp0/1 registers remain
> unchanged.
>
> Changing the
>
> W16 current_flags = (W16)ra;
>
> lines to
>
> W16 current_flags = (W16)ctx.reg_flags;
>
> worked for me. (However, this might not be quite clean with regard to uop
> issue vs commit semantics.)
>
> I came across this error when investigating spurious Linux kernel freezes
> after
> scheduler timer interrupts.
>
>
> Regards,
>
> gunnar.
>
>
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>
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