Thanks for the test case.
The problem is that we have raised the UDEF exception,
and then the qemu kernel emulation code has decided that
we should emulate the instruction as an FPE11 instruction.
Which seems clearly incorrect, given we're in thumb mode.
** Changed in: qemu
Status: Invalid => In Progress
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https://bugs.launchpad.net/bugs/1925512
Title:
UNDEFINED case for instruction BLX
Status in QEMU:
In Progress
Bug description:
Hi
I refer to the instruction BLX imm (T2 encoding) in ARMv7 (Thumb
mode).
11110 S imm10H 11 J1 0 J2 imm10L H
if H == '1' then UNDEFINED;
I1 = NOT(J1 EOR S); I2 = NOT(J2 EOR S); imm32 =
SignExtend(S:I1:I2:imm10H:imm10L:'00', 32);
targetInstrSet = InstrSet_A32;
if InITBlock() && !LastInITBlock() then UNPREDICTABLE;
According to the manual, if H equals to 1, this instruction should be
an UNDEFINED instruction. However, it seems QEMU does not check this
constraint in function trans_BLX_i. Thanks
Regards
Muhui
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