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target/xtensa: Make use of 'segment' in pptlb helper less confusing 

Coverity gets confused about the use of the 'segment' variable in the
pptlb helper function: it thinks that we can take a code path where
we first initialize it:
  unsigned segment = XTENSA_MPU_PROBE_B;  // 0x40000000
and then use that value as a shift count:
  } else if (nhits == 1 && (env->sregs[MPUENB] & (1u << segment))) {

In fact this isn't possible, beacuse xtensa_mpu_lookup() is passed
'&segment', and it uses that as an output value, which it will always
set if it returns nonzero.  But the way the code is currently written
is confusing to a human reader as well as to Coverity.

Instead of initializing 'segment' at the top of the function with a
value that's only used in the "nhits == 0" code path, use the
constant value directly in that code path, and don't initialize
segment.  This matches the way we use xtensa_mpu_lookup() in its
other callsites in get_physical_addr_mpu().

Resolves: Coverity CID 1547589

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Message-id: 20240723151454.1396826-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2024-07-23 16:14:54 +01:00
parent b69c95e718
commit b42ba4ea43
1 changed files with 2 additions and 2 deletions
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4
target/xtensa/mmu_helper.c
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@ -991,7 +991,7 @@ uint32_t HELPER(rptlb1)(CPUXtensaState *env, uint32_t s)
uint32_t HELPER(pptlb)(CPUXtensaState *env, uint32_t v)
{
unsigned nhits;
unsigned segment = XTENSA_MPU_PROBE_B;
unsigned segment;
unsigned bg_segment;
nhits = xtensa_mpu_lookup(env->mpu_fg, env->config->n_mpu_fg_segments,
@ -1005,7 +1005,7 @@ uint32_t HELPER(pptlb)(CPUXtensaState *env, uint32_t v)
xtensa_mpu_lookup(env->config->mpu_bg,
env->config->n_mpu_bg_segments,
v, &bg_segment);
return env->config->mpu_bg[bg_segment].attr | segment;
return env->config->mpu_bg[bg_segment].attr | XTENSA_MPU_PROBE_B;
}
}