| Message ID | 6ab2ce75-0763-75b1-0d72-ddfb2b9dec19@strupe.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm: ptrace: Fix mask for thumb breakpoint hook | expand |
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 36718a424..f51bec0bc 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -228,9 +228,14 @@ static struct undef_hook arm_break_hook = { .fn = break_trap, }; +/* + * Set all bits in the instruction mask, even though the thumb + * instruction is only 16 bits. This is to prevent accidental + * matching of thumb2 instructions. + */ static struct undef_hook thumb_break_hook = { - .instr_mask = 0xffff, - .instr_val = 0xde01, + .instr_mask = 0xffffffff, + .instr_val = 0x0000de01, .cpsr_mask = PSR_T_BIT, .cpsr_val = PSR_T_BIT, .fn = break_trap,
Since instr_mask in struct undef_hook is 32 bits wide, a mask with value 0xffff will essentially be extended to 0x0000ffff. This makes undefined thumb2 instructions with the second half-word as 0xde01 generate SIGTRAPs instead of SIGILLs. This happens in total for 3143 instructions on my system. An example of such an instruction is e800de01. This patch fixes the issue by extending the mask to the full 32 bits, such that both half-words have to be matched. This will remove all of the accidental matchings, as 0x0000 is not a valid thumb2 prefix, while preserving the intended thumb hook. Signed-off-by: Fredrik Strupe <fredrik@strupe.net> --- arch/arm/kernel/ptrace.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)