Messages in this thread | | | Subject | Re: [PATCH v2] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend | From | Suzuki K Poulose <> | Date | Wed, 8 Apr 2020 12:39:50 +0100 |
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On 04/08/2020 12:29 PM, Fredrik Strupe wrote: > For thumb instructions, call_undef_hook() in traps.c first reads a u16, > and if the u16 indicates a T32 instruction (u16 >= 0xe800), a second > u16 is read, which then makes up the the lower half-word of a T32 > instruction. For T16 instructions, the second u16 is not read, > which makes the resulting u32 opcode always have the upper half set to > 0. > > However, having the upper half of instr_mask in the undef_hook set to 0 > masks out the upper half of all thumb instructions - both T16 and T32. > This results in trapped T32 instructions with the lower half-word equal > to the T16 encoding of setend (b650) being matched, even though the upper > half-word is not 0000 and thus indicates a T32 opcode. > > An example of such a T32 instruction is eaa0b650, which should raise a > SIGILL since T32 instructions with an eaa prefix are unallocated as per > Arm ARM, but instead works as a SETEND because the second half-word is set > to b650. > > This patch fixes the issue by extending instr_mask to include the > upper u32 half, which will still match T16 instructions where the upper > half is 0, but not T32 instructions. > > Signed-off-by: Fredrik Strupe <fredrik@strupe.net> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Fixes: 2d888f48e056 ("arm64: Emulate SETEND for AArch32 tasks") > --- > arch/arm64/kernel/armv8_deprecated.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c > index 9d3442d62..8c06dfee0 100644 > --- a/arch/arm64/kernel/armv8_deprecated.c > +++ b/arch/arm64/kernel/armv8_deprecated.c > @@ -609,7 +609,7 @@ static struct undef_hook setend_hooks[] = { > }, > { > /* Thumb mode */ > - .instr_mask = 0x0000fff7, > + .instr_mask = 0xfffffff7, > .instr_val = 0x0000b650, > .pstate_mask = (PSR_AA32_T_BIT | PSR_AA32_MODE_MASK), > .pstate_val = (PSR_AA32_T_BIT | PSR_AA32_MODE_USR), >
Reviewed-by : Suzuki K Poulose <suzuki.poulose@arm.com>
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