• Fredrik Strupe's avatar
    ARM: 8977/1: ptrace: Fix mask for thumb breakpoint hook · 3866f217
    Fredrik Strupe authored
    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 0xde01 (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
    0xeaa0de01, which is unallocated according to Arm ARM and should raise a
    SIGILL, but instead raises a SIGTRAP.
    
    This patch fixes the issue by setting all the bits in instr_mask, which
    will still match the intended 16-bit thumb instruction (where the
    upper half is always 0), but not any 32-bit thumb instructions.
    
    Cc: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: default avatarFredrik Strupe <fredrik@strupe.net>
    Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
    3866f217
ptrace.c 22.8 KB