Messages in this thread | | | Date | Wed, 8 Apr 2020 18:17:41 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH v2] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend |
| |
On Wed, Apr 08, 2020 at 01:29:41PM +0200, Fredrik Strupe wrote: > For thumb instructions, call_undef_hook() in traps.c first reads a u16, > and if the u16 indicates a T32 instruction (u16 >= 0xe800), a second > u16 is read, which then makes up the the lower half-word of a T32 > instruction. For T16 instructions, the second u16 is not read, > which makes the resulting u32 opcode always have the upper half set to > 0. > > However, having the upper half of instr_mask in the undef_hook set to 0 > masks out the upper half of all thumb instructions - both T16 and T32. > This results in trapped T32 instructions with the lower half-word equal > to the T16 encoding of setend (b650) being matched, even though the upper > half-word is not 0000 and thus indicates a T32 opcode. > > An example of such a T32 instruction is eaa0b650, which should raise a > SIGILL since T32 instructions with an eaa prefix are unallocated as per > Arm ARM, but instead works as a SETEND because the second half-word is set > to b650. > > This patch fixes the issue by extending instr_mask to include the > upper u32 half, which will still match T16 instructions where the upper > half is 0, but not T32 instructions. > > Signed-off-by: Fredrik Strupe <fredrik@strupe.net> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Fixes: 2d888f48e056 ("arm64: Emulate SETEND for AArch32 tasks")
Queued for 5.7. Thanks.
-- Catalin
| |