Data abort with FEAT_PFAR is marked as invalid

[bearzly]

The ESR 0x96004010 was generated by an Arm system that supports FEAT_PFAR. When plugging this into the decoder it returns Invalid ESR, res0 is 0x1

Based on the docs the encoding is

• EC = 0x25 (Data abort)
• IL = 1 (32-bit instruction)
• ISS
  • ISV = 0 (No valid instruction syndrome. ISS[23:14] are RES0.)
  • DFSC = 0b010000 (Synchronous external abort)
  • ISS[14] = 0b1

Since ISV == 0 but ISS[14] is non-zero, the decoder raises an error expecting all the bits to be 0.

However, the docs provide an alternate encoding for bit 14

When FEAT_PFAR is implemented and (DFSC == 0b010000, or DFSC IN {0b01001x}, or DFSC IN {0b0101xx}):
PFV, bit [14]

PFV	Meaning
0b0	
PFAR_EL1 is UNKNOWN.

0b1	
PFAR_EL1 is valid.

There are also a handful of other cases where ISV == 0 that aren't currently handled

[qwandor]

Thanks for the report. Want to send a PR to fix it?