Restore EPC at the branch whose delay slot is emulated if the delay-slot
instruction signals. This is so that code in `fpu_emulator_cop1Handler'
does not see EPC having advanced and mistakenly successfully resume
userland execution from the location at the branch target in that case.
Restoring EPC guarantees an immediate exit from the emulation loop and
if EPC hasn't advanced at all since entering the loop, also issuing the
signal reported by the delay-slot instruction.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9701/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
/*
* Branch taken: emulate dslot instruction
*/
/*
* Branch taken: emulate dslot instruction
*/
+ unsigned long bcpc;
+
+ /*
+ * Remember EPC at the branch to point back
+ * at so that any delay-slot instruction
+ * signal is not silently ignored.
+ */
+ bcpc = xcp->cp0_epc;
xcp->cp0_epc += dec_insn.pc_inc;
contpc = MIPSInst_SIMM(ir);
xcp->cp0_epc += dec_insn.pc_inc;
contpc = MIPSInst_SIMM(ir);
* Single step the non-CP1
* instruction in the dslot.
*/
* Single step the non-CP1
* instruction in the dslot.
*/
- return mips_dsemul(xcp, ir, contpc);
+ sig = mips_dsemul(xcp, ir,
+ contpc);
+ if (sig)
+ xcp->cp0_epc = bcpc;
+ /*
+ * SIGILL forces out of
+ * the emulation loop.
+ */
+ return sig ? sig : SIGILL;
}
} else
contpc = (xcp->cp0_epc + (contpc << 2));
}
} else
contpc = (xcp->cp0_epc + (contpc << 2));
if (cpu_has_mips_2_3_4_5_r)
goto emul;
if (cpu_has_mips_2_3_4_5_r)
goto emul;
/* its one of ours */
goto emul;
/* its one of ours */
goto emul;
case spec_op:
switch (MIPSInst_FUNC(ir)) {
case spec_op:
switch (MIPSInst_FUNC(ir)) {
if (cpu_has_mips_4_5_r)
goto emul;
if (cpu_has_mips_4_5_r)
goto emul;
+
+ bc_sigill:
+ xcp->cp0_epc = bcpc;
+ return SIGILL;
}
/*
* Single step the non-cp1
* instruction in the dslot
*/
}
/*
* Single step the non-cp1
* instruction in the dslot
*/
- return mips_dsemul(xcp, ir, contpc);
+ sig = mips_dsemul(xcp, ir, contpc);
+ if (sig)
+ xcp->cp0_epc = bcpc;
+ /* SIGILL forces out of the emulation loop. */
+ return sig ? sig : SIGILL;
} else if (likely) { /* branch not taken */
/*
* branch likely nullifies
} else if (likely) { /* branch not taken */
/*
* branch likely nullifies
flush_cache_sigtramp((unsigned long)&fr->emul);
flush_cache_sigtramp((unsigned long)&fr->emul);
- return SIGILL; /* force out of emulation loop */
}
int do_dsemulret(struct pt_regs *xcp)
}
int do_dsemulret(struct pt_regs *xcp)