Messages in this thread | | | Subject | Re: [PATCH] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend | From | Suzuki K Poulose <> | Date | Tue, 7 Apr 2020 11:47:26 +0100 |
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On 04/07/2020 10:27 AM, Catalin Marinas wrote: > On Mon, Apr 06, 2020 at 04:16:05PM +0200, Fredrik Strupe wrote: >> Use a full 32-bit mask to prevent accidental matchings of thumb32 >> instructions where the second half-word is equal to the thumb16 setend >> encoding. >> >> This fixes the same problem as the following patch: >> >> https://lkml.org/lkml/2020/3/16/341 > > This link is not guaranteed to be stable and the commit should have the > full description rather than referring to another email. > >> but for setend emulation instead. >> >> Signed-off-by: Fredrik Strupe <fredrik@strupe.net> > > It also needs Fixes: and Cc: stable tags. > >> --- >> 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, > > I can see how this could happen but it would be useful to provide a > concrete example in the commit log. > > The instruction opcode built by call_undef_hook() first reads a u16 as a > T16 instruction and the above should be fine. However, if this looks > like a T32 opcode, it reads a subsequent u16 which becomes the lowest > half-word and the above mask/val may inadvertently match it. >
We also do a check on the pstate_val, along with the instr_val to confirm the mode. So this should be fine as it is ?
Suzuki
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