Messages in this thread | | | Date | Mon, 18 May 2020 15:18:59 +0100 | From | Russell King - ARM Linux admin <> | Subject | Re: [PING] [PATCH v2] arm: ptrace: Fix mask for thumb breakpoint hook |
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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 ?
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