Re: [PING] [PATCH v2] arm: ptrace: Fix mask for thumb breakpoint hook

[Russell King - ARM Linux admin]

On Mon, May 18, 2020 at 03:12:06PM +0200, Fredrik Strupe wrote:
> call_undef_hook() in traps.c applies the same instr_mask for both 16-bit
> and 32-bit thumb instructions. If instr_mask then is only 16 bits wide
> (0xffff as opposed to 0xffffffff), the first half-word of 32-bit thumb
> instructions will be masked out. This makes the function match 32-bit
> thumb instructions where the second half-word is equal to instr_val,
> regardless of the first half-word.
> 
> The result in this case is that all undefined 32-bit thumb instructions
> with the second half-word equal to de01 (udf #1) work as breakpoints
> and will raise a SIGTRAP instead of a SIGILL, instead of just the one
> intended 16-bit instruction. An example of such an instruction is
> eaa0b650, which is unallocated according to Arm ARM and should raise a
> SIGILL, but instead raises a SIGTRAP.

How can 0xeaa0b650 match 0xde01 when masked with 0xffff ?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up