On Mon, May 18, 2020 at 05:02:27PM +0200, Fredrik Strupe wrote: > On 18.05.2020 16:18, Russell King - ARM Linux admin wrote: > > 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 ? > > > > Sorry, that is a typo; it should say 0xeaa0de01. > > For reference, this is similar to the problem with SETEND emulation that > was fixed in commit fc2266011acc in the mainline kernel > (or as discussed here: https://lkml.org/lkml/2020/4/8/274).
Thanks for the clarification. Please update the patch description and put it in the patch system, thanks. -- 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