On 26/07/2019 14:05, Will Deacon wrote:
On Fri, Jul 26, 2019 at 01:38:24PM +0100, Robin Murphy wrote:
On 26/07/2019 13:27, Will Deacon wrote:
On Fri, Jul 26, 2019 at 01:13:54PM +0100, Mark Rutland wrote:
On Fri, Jul 26, 2019 at 01:10:57PM +0100, Mark Rutland wrote:
On Fri, Jul 26, 2019 at 01:27:16PM +0200, Anders Roxell wrote:
When fall-through warnings was enabled by default, commit d93512ef0f0e
("Makefile: Globally enable fall-through warning"), the following
warnings was starting to show up:
../arch/arm64/kernel/hw_breakpoint.c: In function ‘hw_breakpoint_arch_parse’:
../arch/arm64/kernel/hw_breakpoint.c:540:7: warning: this statement may fall
through [-Wimplicit-fallthrough=]
if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
^
../arch/arm64/kernel/hw_breakpoint.c:542:3: note: here
case 2:
^~~~
../arch/arm64/kernel/hw_breakpoint.c:544:7: warning: this statement may fall
through [-Wimplicit-fallthrough=]
if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
^
../arch/arm64/kernel/hw_breakpoint.c:546:3: note: here
default:
^~~~~~~
Rework so that the compiler doesn't warn about fall-through. Rework so
the code looks like the arm code. Since the comment in the function
indicates taht this is supposed to behave the same way as arm32 because
Typo: s/taht/that/
it handles 32-bit tasks also.
Cc: stable@xxxxxxxxxxxxxxx # v3.16+
Fixes: 6ee33c2712fc ("ARM: hw_breakpoint: correct and simplify alignment fixup code")
Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
The patch itself looks fine, but I don't think this needs a CC to
stable, nor does it require that fixes tag, as there's no functional
problem.
Hmm... I now see I spoke too soon, and this is making the 1-byte
breakpoint work at a 3-byte offset.
I still don't think it's quite right though, since it forbids a 2-byte
watchpoint on a byte-aligned address.
Plus, AFAICS, a 1-byte watchpoint on a 2-byte-aligned address.
[and of course, what I missed was that that's the case the fallthrough
serves... yuck indeed]
Not that I know anything about this code, but it does start to look like it
might want rewriting without the offending switch statement anyway. At a
glance, it looks like the intended semantic might boil down to:
if (hw->ctrl.len > offset)
return -EINVAL;
Given that it's compat code, I think it's worth staying as close to the
arch/arm/ implementation as we can.
Right, I also misread the accompanying arch/arm/ patch and got the
impression that 32-bit also had a problem such that any fix would happen
in parallel - on closer inspection the current arch/arm/ code does
actually seem to make sense, even if it is horribly subtle.
Also, beware that the
ARM_BREAKPOINT_LEN_* definitions are masks because of the BAS fields in
the debug architecture.
Fun... Clearly it's a bit too Friday for me to be useful here, so
apologies for the confusion :)
Robin.
