For the Arm target, we have a 3-operand tcg_insn_start,
where the 3 arguments are the PC, condexec bits, and
a syndrome value. We set it up like this:
tcg_gen_insn_start(dc->pc,
(dc->condexec_cond << 4) | (dc->condexec_mask >> 1),
0);
dc->insn_start = tcg_last_op();
and then we patch in the 3rd operand later in disas_set_insn_syndrome():
tcg_set_insn_param(s->insn_start, 2, syn);
Unfortunately, if we're running on a setup where
TARGET_LONG_BITS > TCG_TARGET_REG_BITS (ie 64 bit guest
on 32 bit host), tcg_gen_insn_start() has under the hood
split the 3 operands we gave it into 6, and so we end
up patching a syndrome value into the condexec bits.
This means we'll end up with corrupted guest condexec
state if we have to do a cpu_restore_state(), which happens
often when using icount and occasionally for load/store
instructions that fault.
Fix the bug by using the correct operand offset for the
64-on-32 case.
Cc: qemu-stable@nongnu.org
Reported-by: alarson@ddci.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
This doesn't apply as-is to the stable branch, but the
difference is minor (insn_start was insn_start_idx, but
the 2 vs 4 for argument 2 is still the same.)
---
target/arm/translate.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/target/arm/translate.h b/target/arm/translate.h
index c47febf99d..f04ece9cfd 100644
--- a/target/arm/translate.h
+++ b/target/arm/translate.h
@@ -120,7 +120,15 @@ static inline void disas_set_insn_syndrome(DisasContext *s, uint32_t syn)
/* We check and clear insn_start_idx to catch multiple updates. */
assert(s->insn_start != NULL);
+#if TARGET_LONG_BITS <= TCG_TARGET_REG_BITS
tcg_set_insn_param(s->insn_start, 2, syn);
+#else
+ /* tcg_gen_insn_start has split every target_ulong argument to
+ * op_insn_start into two 32-bit arguments, so we want the low
+ * half of the 3rd argument, which is at index 4.
+ */
+ tcg_set_insn_param(s->insn_start, 4, syn);
+#endif
s->insn_start = NULL;
}
--
2.16.2
On 04/09/2018 08:38 PM, Peter Maydell wrote: > +#if TARGET_LONG_BITS <= TCG_TARGET_REG_BITS > tcg_set_insn_param(s->insn_start, 2, syn); > +#else > + /* tcg_gen_insn_start has split every target_ulong argument to > + * op_insn_start into two 32-bit arguments, so we want the low > + * half of the 3rd argument, which is at index 4. > + */ > + tcg_set_insn_param(s->insn_start, 4, syn); > +#endif > Ouch, good catch. I think we should fix this in tcg_set_insn_param instead, as several other targets are also affected by this. r~
On 9 April 2018 at 23:09, Richard Henderson <rth@twiddle.net> wrote: > On 04/09/2018 08:38 PM, Peter Maydell wrote: >> +#if TARGET_LONG_BITS <= TCG_TARGET_REG_BITS >> tcg_set_insn_param(s->insn_start, 2, syn); >> +#else >> + /* tcg_gen_insn_start has split every target_ulong argument to >> + * op_insn_start into two 32-bit arguments, so we want the low >> + * half of the 3rd argument, which is at index 4. >> + */ >> + tcg_set_insn_param(s->insn_start, 4, syn); >> +#endif >> > > Ouch, good catch. > > I think we should fix this in tcg_set_insn_param instead, > as several other targets are also affected by this. Are they? My grep didn't find anybody else using tcg_set_insn_param() except the gen-icount.h code, which isn't using target_long arguments. If we can fix it in the tcg generic code instead that would be nicer than an ifdef here, though. thanks -- PMM
On 04/10/2018 08:13 AM, Peter Maydell wrote: > On 9 April 2018 at 23:09, Richard Henderson <rth@twiddle.net> wrote: >> On 04/09/2018 08:38 PM, Peter Maydell wrote: >>> +#if TARGET_LONG_BITS <= TCG_TARGET_REG_BITS >>> tcg_set_insn_param(s->insn_start, 2, syn); >>> +#else >>> + /* tcg_gen_insn_start has split every target_ulong argument to >>> + * op_insn_start into two 32-bit arguments, so we want the low >>> + * half of the 3rd argument, which is at index 4. >>> + */ >>> + tcg_set_insn_param(s->insn_start, 4, syn); >>> +#endif >>> >> >> Ouch, good catch. >> >> I think we should fix this in tcg_set_insn_param instead, >> as several other targets are also affected by this. > > Are they? My grep didn't find anybody else using > tcg_set_insn_param() except the gen-icount.h code, > which isn't using target_long arguments. Ah, the s390 code I thought I remembered is still sitting on a branch. I shall have to revive that for the next devel cycle... > If we can fix it in the tcg generic code instead that > would be nicer than an ifdef here, though. I am working on this now. r~
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