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target/arm: Don't allow stage 2 page table walks to downgrade to NS 

Bit 63 in a Table descriptor is only the NSTable bit for stage 1
translations; in stage 2 it is RES0.  We were incorrectly looking at
it all the time.

This causes problems if:
 * the stage 2 table descriptor was incorrectly setting the RES0 bit
 * we are doing a stage 2 translation in Secure address space for
   a NonSecure stage 1 regime -- in this case we would incorrectly
   do an immediate downgrade to NonSecure

A bug elsewhere in the code currently prevents us from getting
to the second situation, but when we fix that it will be possible.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230504135425.2748672-2-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2023-05-12 15:43:37 +01:00
parent 67ce09b544
commit 21a4ab8318
1 changed files with 3 additions and 2 deletions
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5
target/arm/ptw.c
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@ -1415,17 +1415,18 @@ static bool get_phys_addr_lpae(CPUARMState *env, S1Translate *ptw,
descaddrmask &= ~indexmask_grainsize;
/*
* Secure accesses start with the page table in secure memory and
* Secure stage 1 accesses start with the page table in secure memory and
* can be downgraded to non-secure at any step. Non-secure accesses
* remain non-secure. We implement this by just ORing in the NSTable/NS
* bits at each step.
* Stage 2 never gets this kind of downgrade.
*/
tableattrs = is_secure ? 0 : (1 << 4);
next_level:
descaddr |= (address >> (stride * (4 - level))) & indexmask;
descaddr &= ~7ULL;
nstable = extract32(tableattrs, 4, 1);
nstable = !regime_is_stage2(mmu_idx) && extract32(tableattrs, 4, 1);
if (nstable) {
/*
* Stage2_S -> Stage2 or Phys_S -> Phys_NS