linux-user, fix: Preserve x87 state in signal frames - #423
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The 32-bit signal path invoked destructive FSAVE before building the FXSAVE or XSAVE image. FSAVE initializes the x87 state, so sigreturn restored an empty stack instead of the interrupted state for Minke.MI. Organ CLR suspension. Capture the extended state before filling the legacy FSAVE area. This preserves both signal-frame formats while leaving the initialized x87 state for the handler, matching Linux x86 signal semantics. Tests: - Verify that an x87 value survives SIGUSR1 delivery and sigreturn Signed-off-by: Wenqiang Wei <weiwenqiang@mail.ustc.edu.cn>
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Motivation
An x87 value could be lost or restored into the wrong logical stack slot after a guest signal because the i386 signal frame did not preserve the complete x87 state used by LATX.
Changes
linux-user/i386/signal.c.Validation
ninja -C build32 latx-i386LATX_SOFTFPU=2 build32/latx-i386 latx-x87-signal-stack-test-onesignals=1 failures=0.Scope
This PR contains one correctness fix. LBT TOP cleanup is submitted separately.