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target/arm: Add assertion about FSC format for syndrome registers

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In tlb_fill() we construct a syndrome register value from a
fault status register value which is filled in by arm_tlb_fill().
arm_tlb_fill() returns FSR values which might be in the format
used with short-format page descriptors, or the format used
with long-format (LPAE) descriptors. The syndrome register
always uses LPAE-format FSR status codes.

It isn't actually possible to end up delivering a syndrome
register value to the guest for a fault which is reported
with a short-format FSR (that kind of stage 1 fault will only
happen for an AArch32 translation regime which doesn't have
a syndrome register, and can never be redirected to an AArch64
or Hyp exception level). Add an assertion which checks this,
and adjust the code so that we construct a syndrome with
an invalid status code, rather than allowing set bits in
the FSR input to randomly corrupt other fields in the syndrome.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1491486152-24304-1-git-send-email-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2017-04-20 17:32:29 +01:00
parent 2c4a7cc5af
commit 65ed2ed90d
1 changed files with 18 additions and 5 deletions
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23
target/arm/op_helper.c
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@ -130,7 +130,7 @@ void tlb_fill(CPUState *cs, target_ulong addr, MMUAccessType access_type,
if (unlikely(ret)) {
ARMCPU *cpu = ARM_CPU(cs);
CPUARMState *env = &cpu->env;
uint32_t syn, exc;
uint32_t syn, exc, fsc;
unsigned int target_el;
bool same_el;
@ -145,19 +145,32 @@ void tlb_fill(CPUState *cs, target_ulong addr, MMUAccessType access_type,
env->cp15.hpfar_el2 = extract64(fi.s2addr, 12, 47) << 4;
}
same_el = arm_current_el(env) == target_el;
/* AArch64 syndrome does not have an LPAE bit */
syn = fsr & ~(1 << 9);
if (fsr & (1 << 9)) {
/* LPAE format fault status register : bottom 6 bits are
* status code in the same form as needed for syndrome
*/
fsc = extract32(fsr, 0, 6);
} else {
/* Short format FSR : this fault will never actually be reported
* to an EL that uses a syndrome register. Check that here,
* and use a (currently) reserved FSR code in case the constructed
* syndrome does leak into the guest somehow.
*/
assert(target_el != 2 && !arm_el_is_aa64(env, target_el));
fsc = 0x3f;
}
/* For insn and data aborts we assume there is no instruction syndrome
* information; this is always true for exceptions reported to EL1.
*/
if (access_type == MMU_INST_FETCH) {
syn = syn_insn_abort(same_el, 0, fi.s1ptw, syn);
syn = syn_insn_abort(same_el, 0, fi.s1ptw, fsc);
exc = EXCP_PREFETCH_ABORT;
} else {
syn = merge_syn_data_abort(env->exception.syndrome, target_el,
same_el, fi.s1ptw,
access_type == MMU_DATA_STORE, syn);
access_type == MMU_DATA_STORE, fsc);
if (access_type == MMU_DATA_STORE
&& arm_feature(env, ARM_FEATURE_V6)) {
fsr |= (1 << 11);