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target-arm: A64: Correctly fault FP/Neon if CPACR.FPEN set

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For the A64 instruction set, the only FP/Neon disable trap
is the CPACR FPEN bits, which may indicate "enabled", "disabled"
or "disabled for EL0". Add a bit to the AArch64 tb flags indicating
whether FP/Neon access is currently enabled and make the decoder
emit code to raise exceptions on use of FP/Neon insns if it is not.

We use a new flag in DisasContext rather than borrowing the
existing vfp_enabled flag because the A32/T32 decoder is going
to need both.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
---
I'm aware this is a rather hard to review patch; sorry.
I have done an exhaustive check that we have fp access checks
in all code paths with the aid of the assertions added in the
next patch plus the code-coverage hack patch I posted to the
list earlier.

This patch is correct as of
09e037354 target-arm: A64: Add saturating accumulate ops (USQADD/SUQADD)
which was the last of the Neon insns to be added, so assuming
no refactoring of the code it should be fine.
This commit is contained in:
Peter Maydell 2014-04-15 19:18:39 +01:00
parent 00892383c9
commit 8c6afa6ab1
5 changed files with 320 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

7
target-arm/cpu.c
View file

@ -100,8 +100,15 @@ static void arm_cpu_reset(CPUState *s)
env->pstate = PSTATE_MODE_EL0t;
/* Userspace expects access to CTL_EL0 and the cache ops */
env->cp15.c1_sys |= SCTLR_UCT | SCTLR_UCI;
/* and to the FP/Neon instructions */
env->cp15.c1_coproc = deposit64(env->cp15.c1_coproc, 20, 2, 3);
#else
env->pstate = PSTATE_MODE_EL1h;
#endif
} else {
#if defined(CONFIG_USER_ONLY)
/* Userspace expects access to cp10 and cp11 for FP/Neon */
env->cp15.c1_coproc = deposit64(env->cp15.c1_coproc, 20, 4, 0xf);
#endif
}