arm: Add missing hflag update after writing PSTATE - #2386
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reg_write() for UC_ARM64_REG_PSTATE called pstate_write() but never refreshed env->hflags. The hflags cache holds PSTATE-derived state such as the current exception level, so after a user raises the EL by writing PSTATE, MRS CurrentEL (which materializes the EL as a translate-time constant from the TB flags) and a subsequent ERET still observed the stale level. The sibling UC_ARM64_REG_CP_REG case already calls arm_rebuild_hflags(); do the same after pstate_write(), matching the AArch32 fix in unicorn-engine#2268. Fixes unicorn-engine#2333.
Write PSTATE to raise the exception level to EL2 and check that MRS CurrentEL observes EL2. Without the hflags rebuild the read returns the stale EL1.
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Summary
Fixes #2333.
uc_reg_write(UC_ARM64_REG_PSTATE, ...)calledpstate_write()but did not refreshenv->hflags. QEMU caches PSTATE-derived state (current exception level, SP selection, ...) inhflags, andMRS CurrentELin particular is materialized as a translate-time constant from the TB flags. So after a user raises the exception level by writing PSTATE,MRS CurrentELand a subsequentERETstill observed the stale level.The fix mirrors the existing
UC_ARM64_REG_CP_REGcase (which already callsarm_rebuild_hflags()), and the merged AArch32 counterpart #2268 ("arm: Add missing hflag update after writing xpsr"). Thearm_rebuild_hflagsmechanism itself was introduced for cp-regs in #1844.Before / after
Writing PSTATE to elevate to EL2, then executing
MRS X0, CurrentEL:X0 = 0x4(stale EL1).X0 = 0x8(EL2), matching the written PSTATE.Testing
Added
test_arm64_pstate_hflags_rebuildintests/unit/test_arm64.c: it writes PSTATE to EL2 and assertsMRS CurrentELreports EL2. The assertion fails on the unpatched tree (returns EL1) and passes with the fix. The full unit-test suite passes.Scope
TTBR0/1,MAIR,PAR,VBAR) do not feedhflags, so they need no rebuild.UC_ARM64_REG_CPACR_EL1does feed the SVE-related hflags (SVEEXC_EL/ZCR_LEN); refreshing it is a separate, lower-impact concern that can be handled as a follow-up if desired.arm_rebuild_hflagscall after writing toUC_ARM64_REG_PSTATE? #2333 also mentions a secondary problem (aCurrentELraw_read/fieldoffsetassert); that is out of scope for this change.