• Russell King's avatar
    ARM: VFP: fix emulation of second VFP instruction · 5e4ba617
    Russell King authored
    Martin Storsjö reports that the sequence:
    
            ee312ac1        vsub.f32        s4, s3, s2
            ee702ac0        vsub.f32        s5, s1, s0
            e59f0028        ldr             r0, [pc, #40]
            ee111a90        vmov            r1, s3
    
    on Raspberry Pi (implementor 41 architecture 1 part 20 variant b rev 5)
    where s3 is a denormal and s2 is zero results in incorrect behaviour -
    the instruction "vsub.f32 s5, s1, s0" is not executed:
    
            VFP: bounce: trigger ee111a90 fpexc d0000780
            VFP: emulate: INST=0xee312ac1 SCR=0x00000000
            ...
    
    As we can see, the instruction triggering the exception is the "vmov"
    instruction, and we emulate the "vsub.f32 s4, s3, s2" but fail to
    properly take account of the FPEXC_FP2V flag in FPEXC.  This is because
    the test for the second instruction register being valid is bogus, and
    will always skip emulation of the second instruction.
    
    Cc: <stable@vger.kernel.org>
    Reported-by: default avatarMartin Storsjö <martin@martin.st>
    Tested-by: default avatarMartin Storsjö <martin@martin.st>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    5e4ba617
vfpmodule.c 18.5 KB